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1
Awan, Musarat. "Amblyopia and visual development." Thesis, University of Leicester, 2008. http://hdl.handle.net/2381/9539.
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Background: Amblyopia, ‘lazy’ eye is a unilateral or bilateral reduction in vision for which no organic cause is present by physical examination of the eye with a prevalence of approximately 3.5% of the childhood population. It is commonly associated with a strabismus, refractive error or both. The most common form of treatment is conventional occlusion (daily patching the good eye). Clinical studies have attempted to investigate the optimal treatment of the disease and investigate compliance, however an evidence-base for treatment is still incomplete. Methods: The study included (i) a retrospective study of 322 amblyopic children to assess current visual outcomes in comparison to clinical effort and costs; (ii) A randomised control trial (n=52) comparing prescribed treatments of 0-hours, 3-hours and 6-hours patching per day in which compliance was electronically recorded; (iii) interviews of 25 families to explore reasons behind poor compliance; and (iv) a pilot study of educational material to improve compliance. Results: Current outcomes of amblyopia treatment are mediocre at considerable financial and time-costs. The RCT revealed poor compliance in both patching groups (3-hours and 6-hours) leading to visual improvements that were not significantly better than no patching. However, there was a clear dose-response between visual improvement and effective hours patched (p=0.00013). The interviews demonstrated emotional distress in families, lack of social acceptance, and confusion about amblyopia, its treatment and the role of professionals. Early findings indicate that an educational intervention could reduce the number of poor compliers. Conclusion: Poor compliance leads to poor visual outcomes of occlusion treatment for amblyopia. However, objective monitoring of patching demonstrates that occlusion therapy is effective. An educational intervention could address some of the problems associated with poor compliance such as poor parental understanding, providing feedback of visual improvement to the family and strategies for implementing patching as a normal routine.
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Demanins, Rita. "Spatial vision in strabismic amblyopia." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35960.
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Spatial vision, refers to how the visual system encodes the relationships between simple features in the external world for extraction of meaningful information as to object form and location in space. Amblyopia (from the Greek, meaning "blunt vision") is a developmental monocular deficit arising in an estimated 5% of children and is the most common cause of unilateral blindness in the adult population. The condition is primarily associated with a strabismus (misalignment of an eye) or anisometropia (unequal refractive error in the two eyes) or both (mixed amblyopia) being present at or shortly after birth. The strabismic amblyopic deficit includes a decrease in contrast sensitivity, with an accompanying loss in acuity. This population is unique in that unlike the anisometropic group, they experience spatial distortions and non-contrast dependent anomalous spatial localization. This has led to the proposition that tarachopia or "distorted" vision may be a better descriptive term to use as opposed to amblyopia or "blunt" vision.In an effort to characterize the distortions that strabismic amblyopes perceive, we have quantified the deficit in spatial localization across the dimensions of spatial scale, eccentricity and exposure duration. The results show that: (1) the deficits of spatial localization, spatial uncertainty (increased alignment threshold) and bias (perceived point of subjective alignment) are uncorrelated; (2) both deficits are scale invariant for well separated elements; (3) the form of the regional distribution depends on the spatial measure used and the scale at which it is measured; (4) there is a poor correlation between the deficit for either spatial measure and the contrast sensitivity loss; and (5) spatial uncertainty is invariant with exposure duration.
In addition we have sought to characterize the neural substrate of the spatial deficits. We psychophysically probe the sampling properties of the neuronal population and analyze the dependence of simple pattern discrimination on stimulus bandwidth properties. Our results show that the detection deficit due to neural pooling is effective in limiting the spatial frequencies where sampling considerations are important. Within this region of visible high frequencies, an irregular arrangement of neurons rather than neural loss is the greater contributor to the strabismic amblyopes' deficit. In addition, the amblyopic eye either has broader orientation and spatial frequency detectors or is deficient only for first-order orientation processing.
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Pradeep, Archana. "Can amblyopia treatment be optimised?" Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/38534.
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Demanins, Rita. "Spatial vision in a strabismic amblyopia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0028/NQ50290.pdf.
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Piano, Marianne Emma Florence. "Perceptual visual distortions in human amblyopia." Thesis, Glasgow Caledonian University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676486.
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It has been shown that adults and children with amblyopia can experience metamorphopsia (perceptual visual distortions). This body of work chronicles the piloting of a novel dichoptic technique to quantitatively map perceptual visual distortions in adults with amblyopia. It was demonstrated that perceptual visual distortions as measured with this method were more severe in strabismic amblyopes, were not homogenous across the visual field, and were highly individual to each amblyope, in common with the findings of other studies using alternative distortion mapping methods. It was established that perceptual visual distortions in adult amblyopes remained stable geotopically and in magnitude over time, and were closely associated with the angle of strabismic deviation and strength of binocular single vision - unique findings not documented in the literature previously. The dichoptic paradigm was then used to measure perceptual visual distortions in children with amblyopia at different stages of amblyopia treatment, as no study before had attempted to relate severity of perceptual visual distortions to amblyopia treatment outcomes, or establish how prevalent they were amongst amblyopic children. For the first time, a large sample of amblyopic children was tested (n = 82) and compared to agematched visually normal controls (n = 140). It was established that 56.1% of the sample had perceptual visual distortions, and importantly, that the severity of these was independent of amblyopia treatment outcomes. Instead, as in the adult amblyopes, distortion severity was found to be primarily dictated by strength of binocular function and the size of the angle of deviation. Overall, the key message of this work is the importance of evaluating all aspects of the disruption to visual function in amblyopia, and attempting a unified, binocular treatment approach that addresses these aspects, in the hope of producing better amblyopia treatment outcomes for children in the future.
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Bruce, Alison. "Structural Integrity of Eyes Diagnosed with Amblyopia. The measurement of retinal structure in amblyopia using Optical Coherence Tomography." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4894.
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Amblyopia is the leading cause of monocular visual impairment in children. Therapy for amblyopia is extremely beneficial in some children but ineffective in others. It is critical that the reasons for this discrepancy are understood. Emerging evidence indicates that current clinical protocols for the diagnosis of amblyopia may not be sufficiently sensitive in identifying individuals who, on more detailed examination, exhibit subtle structural defects of the eye. Presently, the magnitude of this problem is unknown. The aim of this study was to establish the prevalence of subtle retinal/optic nerve head defects in eyes diagnosed with amblyopia, to distinguish between possible explanations for the origin of such defects and to investigate the relationship between quantitative measures of retinal structure, retinal nerve fibre layer thickness and optic nerve head dimensions. Using the imaging technique of Optical Coherence Tomography (OCT) retinal structure has been investigated in detail, following the visual pathway across the retina from the fovea, via the paramacular bundle to the optic disc, where peripapillary retinal nerve fibre thickness has been imaged and subjected to detailed measures along with optic disc size and shape. The study formed two phases, the first imaging the eyes of visually normal adults and children, comparing them to amblyopes, both adults and children who had completed their treatment. The second phase, a longitudinal study, investigated retinal structure of amblyopic children undertaking occlusion therapy for the first time. By relating pre-therapy quantitative measures to the visual outcome the second phase of the study aimed to examine whether OCT imaging could identify children achieving a poor final outcome. The results show a clear picture of inter-ocular symmetry structure in all individuals, visually normal and amblyopic. Optic disc characteristics revealed no structural abnormalities in amblyopes, in any of the measured parameters, nor was there any association between the level of visual acuity and the measured structure. At the fovea differences were shown to occur in the presence of amblyopia, with thickening of the fovea and reduction of the foveal pit depth. The structural changes were found to be both bilateral and symmetrical with the fellow eye also affected. In the longitudinal phase of the study these changes were demonstrated to a greater extent in children who 'failed' to respond to treatment. This bilateral, symmetrical structural change found at the fovea, which has not been previously reported, cannot therefore be the primary cause of the visual loss which has been diagnosed as amblyopia.
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Maconachie, Gail Dorothy Elizabeth. "The development and treatment of strabismic amblyopia." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/33165.
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Background: Strabismus development is a complex process involving various parts of the visual system. This complexity is increased by the presence of numerous subtypes. Although research has shown strong genetic and environmental components it is not yet clear if there are stronger associations with particular subtypes. In addition, the association between strabismus and retinal development and its limitation on visual outcome, in combination with other factors such as compliance to treatment, has not yet been explored. Methods: Strabismic subjects were recruited to four areas to assess the development and treatment of strabismic amblyopia. Genetic and environmental factors were systematically identified within the literature and through strabismic pedigrees. The influence of strabismic development on the retina was assessed using optical coherence tomography (OCT) in strabismic infants compared to healthy controls. OCT and electronic monitors were used to investigate causes of poor outcomes after amblyopia treatment. Results: Systematic reviewing of the literature revealed strong associations between strabismus and various environmental and genetic factors. By observing the inheritance of strabismus through pedigrees it was observed that accommodative forms of esotropia had a stronger association with inheritance than other subtypes. The effect of strabismus on retinal development revealed delayed or abnormal changes within particular layers of the retina. These defects were observed in both eyes of strabismic subjects and were sustained in subjects who failed to reach successful outcomes after treatment. In addition, through using electronic monitors, compliance to both glasses wearing and occlusion were significantly correlated to visual outcomes. Conclusion: This thesis continues to support growing evidence that both genetic and environmental factors play a role in strabismus development. Its development also has retrograde effects on the visual pathway in particular the retina, which is sustained unless treatment is successful. In addition, compliance to treatment has shown to be vital in obtaining a successful outcome.
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Conner, Ian Patrick. "fMRI studies of amblyopia pediatric and adult perspectives /." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4077.
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Thesis (Ph. D.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains xi, 199 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
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Aavali, Sridharasundaram Preethi. "The efficacy of video biofeedback treatment of amblyopia." Thesis, Anglia Ruskin University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341655.
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Bossi, Manuela. "Amblyopia : assessment and treatment of binocular visual function." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10054824/.
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Unilateral amblyopia is a common neurodevelopmental syndrome characterized by reduced acuity and contrast sensitivity in the amblyopic eye (AE) & by abnormal inter-ocular visual function, e.g. reduced stereoacuity; without a concomitant etiological dysfunction. Standard treatment consists of a period of optical correction followed, when necessary, by occlusion therapy. Although ~70% children gain vision, this monocular therapy is limited by poor compliance and uncertain impact on stereo-function. Recently, binocular treatments have attempted to “rebalance” vision, by adjusting the intensity of monocular visual inputs (enhancing usage to AE or reducing fellow-eye -FE- one), while stimulating binocular cortical interactions. We have developed a “Balanced Binocular Viewing” (BBV) treatment that has patients spend an hour per day at home watching modified movies while wearing 3D goggles (to control what each eye sees). Movies present a blurred image to the FE and a sharp image to the AE. Performance (compliance and binocular-imbalance) is monitored throughout treatment using the child’s performance on a game, played during movie playback. Two ‘ghost’-stimuli, each made of a mixture of luminance increment/decrement, were presented dichoptically (some visible only through goggles): we quantified the mixture required for the child to be equally likely to report either ghost as ‘whiter’. Treating children (N=22) for 8-24 weeks lead to significant improvement in the AE acuity (mean gain: 0.27 logMAR). This is comparable to results achieved with occlusion, but elicits much higher compliance (89% of prescribed daily dose). We also compared our measure of binocular-imbalance to others, also quantifying sensory eye-dominance, to assess any test’s suitability to complement clinical practice. Pilot data measured with adult and children, with and without amblyopia, suggest that a variant of the ’ghost’-game is a potentially useful and efficient stand-alone clinical test with the advantage of being suitable for unsupervised home-based monitoring of patient’s binocular status.
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Chu, Chung-yin, and 朱仲賢. "Factors for suboptimal compliance and outcome in amblyopia treatment for children in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46935460.
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Agrawal, Ritwick. "Psychophysical studies of binocular and spatial vision in humans with anisometropic and strabismic amblyopia." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3497.
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Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains vii, 49 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 45-47).
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Panesar, Gurvinder K. "The functional impact of amblyopia and its associated conditions : an investigation of the potential disability associated with amblyopia and its associated conditions." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/5415.
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In the past decade, considerable attention has been paid to examination of the impact of amblyopia, and strabismus, upon the lives of the individuals. Although an extensive amount of literature exists regarding amblyopia and its associated visual defects, little is known about the contribution of the amblyopic eye in the habitual viewing condition (i.e. both eyes viewing). The purpose of these studies was to determine whether amblyopes are disadvantaged in the performance of tasks under habitual viewing conditions, highlighting any functional differences which may exist as a consequence of amblyopia. Secondly, the work aimed to investigate whether the amblyopic eye contributes to the habitual performance of these tasks. A simple light detection task, in a dichoptic arrangement based upon blue/yellow stimuli viewed through yellow filters, was used to investigate the above two aims and investigate the degree of interocular suppression in amblyopic participants. Using a 3D motion analysis system performance was assessed for an obstacle crossing task (adaptive gait) and a task of reaching for and grasping of an isolated object and in a 'cluttered' environment. Fine motor skills were assessed in a threading a needle task. On the whole it was found that amblyopes are not disadvantaged under habitual viewing conditions, and in cases where differences were found to exist this appeared to be in tasks requiring speed and accuracy. Consistently across all studies it was found that the amblyopic eye contributed in a positive manner, thus, as in visual normals, two eyes are better than one.
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Waddingham, Paula E. "Application of virtual reality in the treatment of amblyopia." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490842.
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Amblyopia is the term used to describe a loss of vision which has occurred as the result of a significant interruption of the normal visual development. Amblyopia, which is more commonly known as 'lazy eye', affects 2-3% of the population, but is a potentially reversible condition.
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Levi, D. M., David J. Whitaker, and A. Provost. "Amblyopia masks the scale invariance of normal human vision." ARVO, 2009. http://hdl.handle.net/10454/4549.
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noIn normal vision, detecting a kink (a change in orientation) in a line is scale invariant: it depends solely on the length/width ratio of the line (D. Whitaker, D. M. Levi, & G. J. Kennedy, 2008). Here we measure detection of a change in the orientation of lines of different length and blur and show that strabismic amblyopia is qualitatively different from normal foveal vision, in that: 1) stimulus blur has little effect on performance in the amblyopic eye, and 2) integration of orientation information follows a different rule. In normal foveal vision, performance improves in proportion to the square root of the ratio of line length to blur (L: B). In strabismic amblyopia improvement is proportional to line length. Our results are consistent with a substantial degree of internal neural blur in first-order cortical filters. This internal blur results in a loss of scale invariance in the amblyopic visual system. Peripheral vision also shows much less effect of stimulus blur and a failure of scale invariance, similar to the central vision of strabismic amblyopes. Our results suggest that both peripheral vision and strabismic amblyopia share a common bottleneck in having a truncated range of spatial mechanisms-a range that becomes more restricted with increasing eccentricity and depth of amblyopia.
Leverhulme Trust, Wellcome Trust, NIH
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Renström, Björkdahl Jeanette. "Följsamhet vid ocklusionsbehandling : - hur kan ögonsjuksköterskan främja den?" Thesis, Högskolan i Halmstad, Akademin för hälsa och välfärd, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-36948.
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Följsamheten av ocklusionsbehandling hos barn med amblyopi är bristfällig. Det finns begränsat med forskning om vilka erfarenheter vårdpersonal har av denna bristande följsamhet, och det vore därför av intresse att undersöka vilka åtgärder ögonsjuksköterskor upplever kan vidtas för att främja följsamheten. Syftet med pilotstudien var därför att undersöka hur ögonsjuksköterskan kan främja följsamhetenav ocklusionsbehandling. Studien genomfördes som en beskrivande, kvalitativ pilotstudie med induktiv ansats där data analyserades med manifest kvalitativ dataanalys. I resultatet framkom fem kategorier, vilka påvisade vikten av att ögonsjuksköterskor tänker på att bemöta vårdnadshavare och barn med ett icke-dömande förhållningssätt, att ge tydlig och individanpassad information både muntligt och skriftligt, samt olika praktiska råd kring själva genomförandet av behandlingen. I resultatet framkom även vikten av att skapa en personlig relation vårdpersonal, vårdnadshavare och barn emellan och betydelsen av täta återbesök, samt hur ett gott samarbete och stöd kollegor emellan kan främja följsamheten. Rekommendationer för vårdverksamhet är bland annat att ge vårdnadshavare och barn kontinuitet vid besöken och rekommendationer för utbildning inom omvårdnad att lära ut vikten av ett positivt förhållningssätt och att ställa öppna frågor. Större studier med samma syfte är av intresse, samt forskning kring hur information på internet påverkar följsamheten.Adherence to occlusion therapy with amblyopic children is inadequate. There is limited with research about medical staff’s experiences of inadequate occlusion therapy. Therefore it is of importance investigating which arrangements ophthalmic nurses’ perceive can be taken to improve adherence. The purpose of this pilot study was to investigate how ophthalmic nurses can improve adherence to occlusion therapy. The study was conducted as a descriptive, qualitative pilot study with an inductive approach where data was analyzed with manifest qualitative content analysis. Five different categories were revealed and showed the importance of a non-judgmental attitude among ophthalmic nurses towards the child and the caregivers, the importance of giving both verbal and written comprehensible, individualized information. Practical advice about carrying out the occlusion therapy emerged in the data along with the importance of creating a personal relationship between the medical staff and the child/caregiver. Frequent revisits were seen as important, and good support and cooperation between colleagues was believed to be able to improve adherence. Recommendations for care activities is to give the child and the caregivers continuity during visits and a recommendation for nursingeducation is to teach the importance of a positive attitude and open-ended questions. Larger studies with the same purpose are of interest, also further research of how information on the internet affects adherence to occlusion therapy.
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Vedamurthy, Indu Optometry & Vision Science Faculty of Science UNSW. "Interocular interactions in normal and amblyopic visual systems." Awarded by:University of New South Wales. School of Optometry and Vision Science, 2006. http://handle.unsw.edu.au/1959.4/24931.
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The aim of this study was to add to our understanding of interocular interactions in normally sighted children (Group I, N=20), normal adults (Group II, N=20) and adults with anisometropic amblyopia (N=12) by investigating responses to a range of visual functions under three kinds of viewing condition. Visual functions tested were visual acuity, contrast sensitivity and alignment sensitivity. Stimuli were generated on a Cambridge VSG card driving a high resolution monitor and FE liquid crystal goggles, enabling three kinds of viewing conditions: 1. Monocular (non-tested eye occluded), used as a baseline for most functions. 2. Dichoptic (uniform field presented to the non-tested eye but with a binocular fusion lock). 3. Binocular. In general, binocular performance was better than monocular (binocular summation) but so too was dichoptic performance (dichoptic advantage). However there was much variation within individuals (the three functions showing different summation/advantage pattern) and between individuals. Significant conclusions include: (a) Maturational windows for interocular interactions differ for different spatial visual functions. (b) Interpretations of results from one visual function cannot be applied automatically to other functions. (c) Care must be taken in interpreting results based on 5 or fewer subjects.
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Ho, Cindy. "Low- and high-level motion deficits in amblyopia: studies of maximum motion displacement." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/285.
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The human visual system comprises two neural pathways, the magnocellular/M and parvocellular/P pathways that process aspects of motion and form perception, respectively. Amblyopia is a developmental condition which may affect an otherwise healthy eye if it experiences abnormal visual stimulation due to ocular misalignment (strabismus), unequal refractive errors (anisometropia), or both. Amblyopia has been associated with deficits in both form and motion perception.
Random-dot kinematograms (RDKs) which are created by shifting a computer-generated dot display in one direction by a given displacement can be used to assess motion processing. Maximum motion displacement (Dmax) is the largest dot displacement at which the direction of motion for a RDK can be correctly discriminated. Strabismic and anisometropic amblyopia represent two distinct subtypes of amblyopia and have been proposed to have different neural substrates. They have also been reported to have different Dmax deficits (Ho et al., 2005).
The intentions of this thesis were: 1) to characterize deficits in Dmax for direction discrimination in the fellow and amblyopic eyes of participants with anisometropic and strabismic amblyopia using psychophysical methods; and 2) to investigate the relationship between psychophysical Dmax deficits and dysfunction in motion-sensitive extrastriate cortex of the M pathway using functional MRI techniques.
The psychophysical results showed that Dmax thresholds are smaller in both amblyopic and fellow eyes for both subtypes of amblyopia relative to controls, although the deficits were greatest for strabismic amblyopia. Functional MRI results revealed decreased extrastriate cortical activation in both the strabismic and anisometropic groups relative to the control group when either eye viewed the RDK stimulus, although the lack of cortical activation was greatest for strabismic amblyopia. Taken together, this evidence suggests that dysfunctional binocular motion processing mechanisms in extrastriate cortex are part of the neural deficit underlying anisometropic and strabismic amblyopia and implies that strabismic amblyopia may be affected to a greater degree.
For both amblyopic groups, there was a robust correlation between depth perception (stereoacuity) and Dmax thresholds. Specifically, direction discrimination was better when stereoacuity was worse. Abnormal binocular integration may have a significant role in predicting motion deficits in both anisometropic and strabismic amblyopia.
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Pitrolo, Yuenan Sun. "fMRI studies of binocular suppression in human amblyopic subjects." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4743.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains vii, 94 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 83-94).
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Astle, Andrew. "A study of perceptual learning effects in human adult amblyopia." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537787.
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Davis, Alison Ruth. "Investigation of the effect of age of onset on amblyopia." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1445483/.
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This research aimed to investigate if age of onset affects the pathogenesis of amblyopia. Amblyopic subjects were compared with normal controls. Strabismic amblyopes were assigned to early or late onset groups on the basis of detailed clinical history. Confirmatory histories were obtained from parents where possible. Contrast Sensitivity (CS) to a 3.2 cyc/deg (cpd) sinusoidal grating pattern was recorded. Monocular pattern appearance visual evoked potentials (VEP) at five contrast levels were recorded. Luminance and chromatic CS, motion onset and colour VEPs were recorded. Late onset amblyopes showed reduced CS at 3.2 cpd for the amblyopic, but increased CS for the fellow eye compared to normal. Late onset amblyopic eye VEP CII latencies were longer and amplitudes smaller than normal. CII responses in amblyopic and fellow eyes of the early onset group were of shorter latency and smaller amplitude than normal. Late onset amblyopes had reduced luminance CS of the amblyopic compared to fellow eyes. Fellow eye chromatic CS was lower than normal in all eyes. The (M-P)/M ratio was greater in the late onset amblyopic eyes. This ratio was increased in all fellow eyes compared to normal. All amblyopes had shorter N200 latencies for both eyes compared to normal. Late onset amblyopic eye VEP N130 latency was longer than in early amblyopes. Early onset amblyopic eye N130 amplitude was smaller than fellow eye amplitude. Results were independent of visual acuity. Different patterns of contrast abnormality occur in early and late onset amblyopes. Late onset amblyopes have a greater parvocellular (P) deficit. Magnocellular (M) results suggest an enhancement of this pathway in all amblyopes. Fellow eyes of amblyopes are abnormal. Examining children during treatment for amblyopia would develop these hypotheses. The changes observed in the M and P pathways could be used to develop treatment strategies in the future.
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Pallet, Lauren J. "Screening of Children Study: Evaluation of Tests of Suppression." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492616795726485.
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Knox, Pamela Jane. "Global motion processing, binocular interactions and perceptual learning in human amblyopia." Thesis, Glasgow Caledonian University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687405.
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Amblyopia, a developmental disorder of the visual system, is widely known to cause a reduction in optotype acuity but it can also be associated with disrupted binocular vision, reduced contrast sensitivity and many other subtle high level visual processing deficits. The initial stages of the work presented in this thesis involved laboratory investigation of the functional visual deficit in global motion processing that has previously been reported abnormal in the presence of amblyopia. The key question is whether higher-levels of visual processing "inherit" abnormalities from lower levels, or whether additional developmental abnormalities arise in direct consequence of impoverished visual input. Overall, the results imply a far more complex perceptual change in amblyopia than would be predicted by the well -established losses in resolution and contrast sensitivity. The motivation behind Chapters 5 and 6 stems from the current observation that the recovery of visual function in amblyopia is contingent on even brief periods of correlated binocular vision, suggesting that amblyopia is intrinsically a binocular problem and that it is suppressive mechanisms that render the cortex, which is a structurally binocular system, functionally monocular. Research is now casting doubts on the idea that amblyopes do not possess cortical binocular connections, suggesting an active suppression rather than a deficit of cellular function. Interestingly, this is echoed in the clinical domain where, in cases of de-correlated visual input, strabismus clinical protocols have now established that the correction of refractive error alone can be sufficient to improve acuity, again implying incomplete inhibition mechanisms. The clinical investigations in this thesis have involved the validation of a series of psychophysical paradigms in cohorts of juvenile and adult amblyopes (as well as age-matched controls) to establish the degree of binocular interaction present and to explore the potential for treating amblyopia with prolonged viewing of a binocular stimulus adapted to correlate the visual imput from both eyes.
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Nicol, David Speirs. "Cortical evoked potentials to flicker, motion and stereoscopic stimuli in amblyopia." Thesis, Glasgow Caledonian University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.688259.
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Vianya-Estopa, Marta, David B. Elliott, and Brendan T. Barrett. "An evaluation of the Amblyopia and Strabismus Questionnaire using Rasch analysis." Association for Research in Vision and Ophthalmology, 2010. http://hdl.handle.net/10454/4730.
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noPURPOSE. To evaluate whether the Amblyopia and Strabismus Questionnaire (A&SQ) is a suitable instrument for the assessment of vision-related quality-of life (VR-QoL) in individuals with strabismus and/or amblyopia. METHODS. The A&SQ was completed by 102 individuals, all of whom had amblyopia, strabismus, or both. Rasch analysis was used to evaluate the usefulness of individual questionnaire items (i.e., questions); the response-scale performance; how well the items targeted VR-QoL; whether individual items showed response bias, depending on factors such as whether strabismus was present; and dimensionality. RESULTS. Items relating to concerns about the appearance of the eyes were applicable only to those with strabismus, and many items showed large ceiling effects. The response scale showed disordered responses and underused response options, which improved after the number of response options was reduced from five to three. This change improved the discriminative ability of the questionnaire (person separation index increased from 1.98 to 2.11). Significant bias was found between strabismic and nonstrabismic respondents. Separate Rasch analyses conducted for subjects with and without strabismus indicated that all A&SQ items seemed appropriate for individuals with strabismus (Rasch infit values between 0.60 and 1.40), but several items fitted the model poorly in amblyopes without strabismus. The AS&Q was not found to be unidimensional. CONCLUSIONS. The findings highlight the limitations of the A&SQ instrument in the assessment of VR-QoL in subjects with strabismus and especially in those with amblyopia alone. The results suggest that separate instruments are needed to quantify VR-QoL in amblyopes with and without strabismus.
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Webber, Ann Louise. "The effect of Amblyopia on motor and psychosocial skills in children." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/30211/1/Ann_Webber_Thesis.pdf.
Full textAbstract:
Background/Aims: In an investigation of the functional impact of amblyopia on children, the fine motor skills, perceived self-esteem and eye movements of amblyopic children were compared with that of age-matched controls. The influence of amblyogenic condition or treatment factors that might predict any decrement in outcome measures was investigated.
The relationship between indirect measures of eye movements that are used clinically and eye movement characteristics recorded during reading was examined and the relevance of proficiency in fine motor skills to performance on standardised educational tests was explored in a sub-group of the control children.
Methods: Children with amblyopia (n=82; age 8.2 ± 1.3 years) from differing causes (infantile esotropia n=17, acquired strabismus n=28, anisometropia n=15, mixed n=13 and deprivation n=9), and a control group of children (n=106; age 9.5 ± 1.2 years) participated in this study. Measures of visual function included monocular logMAR visual acuity (VA) and stereopsis assessed with the Randot Preschool Stereoacuity test, while fine motor skills were measured using the Visual-Motor Control (VMC) and Upper Limb Speed and Dexterity (ULSD) subtests of the Brunicks-Oseretsky Test of Motor Proficiency. Perceived self esteem was assessed for those children from grade 3 school level with the Harter Self Perception Profile for Children and for those in younger grades (preschool to grade 2) with the Pictorial Scale of Perceived Competence and Acceptance for Young Children. A clinical measure of eye movements was made with the Developmental Eye Movement (DEM) test for those children aged eight years and above. For appropriate case-control comparison of data, the results from amblyopic children were compared with age-matched sub-samples drawn from the group of children with normal vision who completed the tests. Eye movements during reading for comprehension were recorded by the Visagraph infra-red recording system and results of standardised tests of educational performance were also obtained for a sub-set of the control group.
Results Amblyopic children (n=82; age 8.2 ± 1.7 years) performed significantly poorer than age-matched control children (n=37; age 8.3 ± 1.3 years) on 9 of 16 fine motor skills sub-items and for the overall age-standardised scores for both VMC and ULSD items (p<0.05); differences were most evident on timed manual dexterity tasks. The underlying aetiology of amblyopia and level of stereoacuity significantly affected fine motor skill performance on both items. However, when examined in a multiple regression model that took into account the inter-correlation between visual characteristics, poorer fine motor skills performance was only associated with strabismus (F1,75 = 5.428; p =0. 022), and not with the level of stereoacuity, refractive error or visual acuity in either eye.
Amblyopic children from grade 3 school level and above (n=47; age 9.2 ± 1.3 years), particularly those with acquired strabismus, had significantly lower social acceptance scores than age-matched control children (n=52; age 9.4 ± 0.5 years) (F(5,93) = 3.14; p = 0.012). However, the scores of the amblyopic children were not significantly different to controls for other areas related to self-esteem, including scholastic competence, physical appearance, athletic competence, behavioural conduct and global self worth. A lower social acceptance score was independently associated with a history of treatment with patching but not with a history of strabismus or wearing glasses. Amblyopic children from pre-school to grade 2 school level (n=29; age = 6.6 ± 0.6 years) had similar self-perception scores to their age-matched peers (n=20; age = 6.4 ± 0.5 years).
There were no significant differences between the amblyopic (n=39; age 9.1 ± 0.9 years) and age-matched control (n = 42; age = 9.3 ± 0.38 years) groups for any of the DEM outcome measures (Vertical Time, Horizontal Time, Number of Errors and Ratio (Horizontal time/Vertical time)). Performance on the DEM did not significantly relate to measures of VA in either eye, level of binocular function, history of strabismus or refractive error.
Developmental Eye Movement test outcome measures Horizontal Time and Vertical Time were significantly correlated with reading rates measured by the Visagraph for both reading for comprehension and naming numbers (r>0.5). Some moderate correlations were also seen between the DEM Ratio and word reading rates as recorded by Visagraph (r=0.37).
In children with normal vision, academic scores in mathematics, spelling and reading were associated with measures of fine motor skills. Strongest effect sizes were seen with the timed manual dexterity domain, Upper Limb Speed and Dexterity.
Conclusions Amblyopia may have a negative impact on a child’s fine motor skills and an older child’s sense of acceptance by their peers may be influenced by treatment that includes eye patching. Clinical measures of eye movements were not affected in amblyopic children.
A number of the outcome measures of the DEM are associated with objective recordings of reading rates, supporting its clinical use for identification of children with slower reading rates. In children with normal vision, proficiency on clinical measures of fine motor skill are associated with outcomes on standardised measures of educational performance. Scores on timed manual dexterity tasks had the strongest association with educational performance.
Collectively, the results of this study indicate that, in addition to the reduction in visual acuity and binocular function that define the condition, amblyopes have functional impairment in childhood development skills that underlie proficiency in everyday activities. The study provides support for strategies aimed at early identification and remediation of amblyopia and the co-morbidities that arise from abnormal visual neurodevelopment.
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Webber, Ann Louise. "The effect of Amblyopia on motor and psychosocial skills in children." Queensland University of Technology, 2009. http://eprints.qut.edu.au/30211/.
Full textAbstract:
Background/Aims: In an investigation of the functional impact of amblyopia on children, the fine motor skills, perceived self-esteem and eye movements of amblyopic children were compared with that of age-matched controls. The influence of amblyogenic condition or treatment factors that might predict any decrement in outcome measures was investigated.
The relationship between indirect measures of eye movements that are used clinically and eye movement characteristics recorded during reading was examined and the relevance of proficiency in fine motor skills to performance on standardised educational tests was explored in a sub-group of the control children.
Methods: Children with amblyopia (n=82; age 8.2 ± 1.3 years) from differing causes (infantile esotropia n=17, acquired strabismus n=28, anisometropia n=15, mixed n=13 and deprivation n=9), and a control group of children (n=106; age 9.5 ± 1.2 years) participated in this study. Measures of visual function included monocular logMAR visual acuity (VA) and stereopsis assessed with the Randot Preschool Stereoacuity test, while fine motor skills were measured using the Visual-Motor Control (VMC) and Upper Limb Speed and Dexterity (ULSD) subtests of the Brunicks-Oseretsky Test of Motor Proficiency. Perceived self esteem was assessed for those children from grade 3 school level with the Harter Self Perception Profile for Children and for those in younger grades (preschool to grade 2) with the Pictorial Scale of Perceived Competence and Acceptance for Young Children. A clinical measure of eye movements was made with the Developmental Eye Movement (DEM) test for those children aged eight years and above. For appropriate case-control comparison of data, the results from amblyopic children were compared with age-matched sub-samples drawn from the group of children with normal vision who completed the tests. Eye movements during reading for comprehension were recorded by the Visagraph infra-red recording system and results of standardised tests of educational performance were also obtained for a sub-set of the control group.
Results Amblyopic children (n=82; age 8.2 ± 1.7 years) performed significantly poorer than age-matched control children (n=37; age 8.3 ± 1.3 years) on 9 of 16 fine motor skills sub-items and for the overall age-standardised scores for both VMC and ULSD items (p<0.05); differences were most evident on timed manual dexterity tasks. The underlying aetiology of amblyopia and level of stereoacuity significantly affected fine motor skill performance on both items. However, when examined in a multiple regression model that took into account the inter-correlation between visual characteristics, poorer fine motor skills performance was only associated with strabismus (F1,75 = 5.428; p =0. 022), and not with the level of stereoacuity, refractive error or visual acuity in either eye.
Amblyopic children from grade 3 school level and above (n=47; age 9.2 ± 1.3 years), particularly those with acquired strabismus, had significantly lower social acceptance scores than age-matched control children (n=52; age 9.4 ± 0.5 years) (F(5,93) = 3.14; p = 0.012). However, the scores of the amblyopic children were not significantly different to controls for other areas related to self-esteem, including scholastic competence, physical appearance, athletic competence, behavioural conduct and global self worth. A lower social acceptance score was independently associated with a history of treatment with patching but not with a history of strabismus or wearing glasses. Amblyopic children from pre-school to grade 2 school level (n=29; age = 6.6 ± 0.6 years) had similar self-perception scores to their age-matched peers (n=20; age = 6.4 ± 0.5 years).
There were no significant differences between the amblyopic (n=39; age 9.1 ± 0.9 years) and age-matched control (n = 42; age = 9.3 ± 0.38 years) groups for any of the DEM outcome measures (Vertical Time, Horizontal Time, Number of Errors and Ratio (Horizontal time/Vertical time)). Performance on the DEM did not significantly relate to measures of VA in either eye, level of binocular function, history of strabismus or refractive error.
Developmental Eye Movement test outcome measures Horizontal Time and Vertical Time were significantly correlated with reading rates measured by the Visagraph for both reading for comprehension and naming numbers (r>0.5). Some moderate correlations were also seen between the DEM Ratio and word reading rates as recorded by Visagraph (r=0.37).
In children with normal vision, academic scores in mathematics, spelling and reading were associated with measures of fine motor skills. Strongest effect sizes were seen with the timed manual dexterity domain, Upper Limb Speed and Dexterity.
Conclusions Amblyopia may have a negative impact on a child’s fine motor skills and an older child’s sense of acceptance by their peers may be influenced by treatment that includes eye patching. Clinical measures of eye movements were not affected in amblyopic children.
A number of the outcome measures of the DEM are associated with objective recordings of reading rates, supporting its clinical use for identification of children with slower reading rates. In children with normal vision, proficiency on clinical measures of fine motor skill are associated with outcomes on standardised measures of educational performance. Scores on timed manual dexterity tasks had the strongest association with educational performance.
Collectively, the results of this study indicate that, in addition to the reduction in visual acuity and binocular function that define the condition, amblyopes have functional impairment in childhood development skills that underlie proficiency in everyday activities. The study provides support for strategies aimed at early identification and remediation of amblyopia and the co-morbidities that arise from abnormal visual neurodevelopment.
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Malmsten, Oscar. "Ortoptisters upplevelser av vad som påverkar följsamhet till amblyopibehandling hos barn." Thesis, Linnéuniversitetet, Institutionen för hälso- och vårdvetenskap (HV), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-65796.
Full textAbstract:
Bakgrund: Amblyopi är en synnedsättning som uppkommer under de första levnadsåren och orsakas av bristande stimulans eller hämning av celler i synbarken. Följsamhet till behandlingen är viktig hos barn med amblyopi för att kunna utveckla en optimal synskärpa. En dålig följsamhet kan leda till bestående synnedsättning, ökat lidande och minskad livskvalitet. Följsamhet kan kopplas till de tre engelska termerna compliance, adherence och concordance, som definieras på olika sätt.
Syfte: Syftet med studien var att ur ortoptistens perspektiv belysa vad som är av betydelse för följsamhet vid behandling av barn med amblyopi.
Metod: Data samlades in genom nio intervjuer med verksamma ortoptister. Databearbetning genomfördes med hjälp av kvalitativ innehållsanalys.
Resultat: I resultatet framträder fyra områden som påverkar följsamheten. Barnets förutsättningar, hur behandlingen hanteras, kommunikation och behandlingens utformning, resultat och påverkan i vardagen upplevs av ortoptisterna som faktorer som både främjar och försvårar följsamheten. Mycket av resultatet stämmer överens med tidigare forskning, men att ortoptisterna upplever att familjekonstellation och bemötande har betydelse för följsamhet är nytt.
Slutsats: Vid amblyopibehandling hos barn är det nödvändigt att ortoptisten har kunskap om och förståelse för vad som har betydelse för följsamhet. Med denna kunskap kan ortoptisten på flera områden verka för ett bättre behandlingsresultat där barnet uppnår optimal synskärpa. Ortoptistens syn på följsamhet påverkar på vilket sätt som hen får ansvar för barnets följsamhet.
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Shea, Sarah Jayne. "Motion VEPs in early onset strabismus." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343703.
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Wolf, Janet Elizabeth. "Identification of defects in specific parallel #channels' of the human visual system." Thesis, City University London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319690.
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Kendall, Bridget. "The effect of strabismic amblyopia on the central visual field of children." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37829.pdf.
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Cleary, Marie. "Clinical evaluation of fixation characteristics and visual acuity outcomes in human amblyopia." Thesis, Glasgow Caledonian University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370008.
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Kanonidou, Evgenia. "An investigation into reading ability using eye movement recordings in strabismic amblyopia." Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/9935.
Full textAbstract:
1. Introduction 1.1 Amblyopia 1.1.1 Definition Amblyopia or „lazy eye‟ has conventionally been defined as “a unilateral or bilateral decrease of visual acuity caused by deprivation of pattern vision or abnormal binocular interaction, for which no cause can be detected by physical examination of the eye and which in some cases can be reversed by therapeutic measures” (1). Clinically, amblyopia is defined as a reduction in best-corrected visual acuity to less than 6/9 monocularly in Snellen optotype or as a two-line difference or more in best-corrected visual acuity between the eyes in LogMAR optotype. This compares with findings in normal subjects, in which the interocular difference in best-corrected visual acuity has been found to be less than two lines (0.2 LogMAR optotype) in both infants and adults (2). However, clinical definitions are debated with different studies using different inclusion criteria for the amblyopic subjects participated. 1.1.2 Prevalence Amblyopia is a significant cause of unilateral visual deficit in childhood and is still considered as one of the most common causes of persistent unilateral visual impairment in adulthood, including populations in which advanced medical care is offered. The prevalence of amblyopia detected in children is estimated between 0.2-5.4% (3-30, 30-35) and in adults between 0.35-3.6% (36-41). It is also classified among the major causes of unilateral visual loss in visually impaired children (13, 42-47) and adults (48-60), in parallel with refractive error, retinal lesions, cataract, corneal opacities and age-related macular degeneration. However, prevalence estimates of amblyopia are affected by the criteria of visual loss used to define amblyopia, the socio-economic properties of the population, the efficacy of the applied screening programmes for amblyopia and amblyogenic risk factors and the effectiveness of the prescribed treatment regimens (1, 24, 61-72). 1.1.3 Aetiology Amblyopia is a form of cerebral visual impairment, in the absence of an organic cause (73-76). It is considered to derive from the degradation of the retinal image associated with abnormal visual experience during the developmental period of the visual system in infancy and early childhood (73-76). Children with anisometropia, strabismus or any other condition causing a reduction in the clarity of the image in one or both eyes, thereby disrupting equal binocular vision, are at risk of developing amblyopia (74-76). Amblyopia is therefore classified according to the type of pathology underlying the abnormal binocular interaction and/or form vision deprivation as (1, 77): (i) Anisometropic, in which a difference in the refractive error between the two eyes represents a risk for developing amblyopia due to creation of dissimilar images; (ii) Strabismic, in which the confusion and diplopia caused by the misalignment of the visual axes of the two eyes can lead to binocular rivalry and suppression of input from the deviating eye at the level of the visual cortex; (iii) Mixed, if anisometropic and strabismic amblyopia co-exist and, (iv) Stimulus deprivation, if there is some obstruction to vision during the sensitive period of visual development (opacities in the media e.g. cataract or severe ptosis). The results of the adult population study of Attebo et al (39) indicated that, the predominant cause of amblyopia was anisometropia in 50%, followed by strabismus in 19%, mixed in 27% and visual deprivation in 4%.
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Beneish, Raquel Gabriela. "Pattern reversal visual evoked potentials in children with strabismic and with anisometropic amblyopia." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61883.
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Kvarnström, Gun. "Visual screening of children in Sweden : epidemiological and methodological aspects /." Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/med852s.pdf.
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Marquardt, Westlake Laura L. "Effectiveness of five vision screening instruments for detecting possible amblyogenetic factors in young children." Laramie, Wyo. : University of Wyoming, 2005. http://proquest.umi.com/pqdweb?did=1051260181&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Algaze, Antonio. "Characterization of the Blood Oxygen Level Dependent Functional Magnetic Resonance Imaging Response in Amblyopia." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039109427.
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Earley, Michael J. "Psychophysical analysis of spatial, temporal and chromatic vision in human refractive and strabismic amblyopia /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487777901661054.
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Simmers, Anita J. "Clinical evaluation of visual dysfunction in human amblyopia and the effect of occlusion therapy." Thesis, Glasgow Caledonian University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360092.
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Göransson, Anne. "Vision in sight : the relationships between knowledge, health beliefs and treatment outcomes : the case of amblyopia /." Linköping : Univ, 1999. http://www.bibl.liu.se/liupubl/disp/disp99/ipp65s.htm.
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Udas, Swati. "Classification algorithms for finding the eye fixation from digital images /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p1418072.
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Vincent, Stephen James. "Ocular characteristics of anisometropia." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/47531/1/Stephen_Vincent_Thesis.pdf.
Full textAbstract:
Animal models of refractive error development have demonstrated that visual experience influences ocular growth. In a variety of species, axial anisometropia (i.e. a difference in the length of the two eyes) can be induced through unilateral occlusion, image degradation or optical manipulation. In humans, anisometropia may occur in isolation or in association with amblyopia, strabismus or unilateral pathology. Non-amblyopic myopic anisometropia represents an interesting anomaly of ocular growth, since the two eyes within one visual system have grown to different endpoints. These experiments have investigated a range of biometric, optical and mechanical properties of anisometropic eyes (with and without amblyopia) with the aim of improving our current understanding of asymmetric refractive error development.
In the first experiment, the interocular symmetry in 34 non-amblyopic myopic anisometropes (31 Asian, 3 Caucasian) was examined during relaxed accommodation. A high degree of symmetry was observed between the fellow eyes for a range of optical, biometric and biomechanical measurements. When the magnitude of anisometropia exceeded 1.75 D, the more myopic eye was almost always the sighting dominant eye. Further analysis of the optical and biometric properties of the dominant and non-dominant eyes was conducted to determine any related factors but no significant interocular differences were observed with respect to best-corrected visual acuity, corneal or total ocular aberrations during relaxed accommodation.
Given the high degree of symmetry observed between the fellow eyes during distance viewing in the first experiment and the strong association previously reported between near work and myopia development, the aim of the second experiment was to investigate the symmetry between the fellow eyes of the same 34 myopic anisometropes following a period of near work. Symmetrical changes in corneal and total ocular aberrations were observed following a short reading task (10 minutes, 2.5 D accommodation demand) which was attributed to the high degree of interocular symmetry for measures of anterior eye morphology, and corneal biomechanics. These changes were related to eyelid shape and position during downward gaze, but gave no clear indication of factors associated with near work that might cause asymmetric eye growth within an individual.
Since the influence of near work on eye growth is likely to be most obvious during, rather than following near tasks, in the third experiment the interocular symmetry of the optical and biometric changes was examined during accommodation for 11 myopic anisometropes. The changes in anterior eye biometrics associated with accommodation were again similar between the eyes, resulting in symmetrical changes in the optical characteristics. However, the more myopic eyes exhibited slightly greater amounts of axial elongation during accommodation which may be related to the force exerted by the ciliary muscle. This small asymmetry in axial elongation we observed between the eyes may be due to interocular differences in posterior eye structure, given that the accommodative response was equal between eyes. Using ocular coherence tomography a reduced average choroidal thickness was observed in the more myopic eyes compared to the less myopic eyes of these subjects. The interocular difference in choroidal thickness was correlated with the magnitude of spherical equivalent and axial anisometropia.
The symmetry in optics and biometrics between fellow eyes which have undergone significantly different visual development (i.e. anisometropic subjects with amblyopia) is also of interest with respect to refractive error development. In the final experiment the influence of altered visual experience upon corneal and ocular higher-order aberrations was investigated in 21 amblyopic subjects (8 refractive, 11 strabismic and 2 form deprivation). Significant differences in aberrations were observed between the fellow eyes, which varied according to the type of amblyopia. Refractive amblyopes displayed significantly higher levels of 4th order corneal aberrations (spherical aberration and secondary astigmatism) in the amblyopic eye compared to the fellow non-amblyopic eye. Strabismic amblyopes exhibited significantly higher levels of trefoil, a third order aberration, in the amblyopic eye for both corneal and total ocular aberrations. The results of this experiment suggest that asymmetric visual experience during development is associated with asymmetries in higher-order aberrations, proportional to the magnitude of anisometropia and dependent upon the amblyogenic factor. This suggests a direct link between the development of higher-order optical characteristics of the human eye and visual feedback.
The results from these experiments have shown that a high degree of symmetry exists between the fellow eyes of non-amblyopic myopic anisometropes for a range of biomechanical, biometric and optical parameters for different levels of accommodation and following near work. While a single specific optical or biomechanical factor that is consistently associated with asymmetric refractive error development has not been identified, the findings from these studies suggest that further research into the association between ocular dominance, choroidal thickness and higher-order aberrations with anisometropia may improve our understanding of refractive error development.
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Chen, Sean Ingram. "The patterns of visual loss and recovery in childhood amblyopia : a prospective, longitudinal treatment study." Thesis, University of Liverpool, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431730.
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Chima, Akash S. "Neural mapping of binocular and amblyopic suppression." Thesis, Anglia Ruskin University, 2015. https://arro.anglia.ac.uk/id/eprint/581521/1/Akash%20S%20Chima%20thesis%20FINAL.pdf.
Full textAbstract:
Inter-ocular suppression occurs when very different images are presented to each eye. Diplopia ensues if different images are superimposed and perceived. The brain removes this unfavourable viewing experience by suppressing one eye’s input to enable clear single vision. Inter-ocular suppression during visual development occurs in response to sufficiently disparate images caused by strabismus (misalignment of the visual axis) or anisometropia (uncorrected difference in refractive error), and if persistent may result in amblyopia. This is reduced visual sensitivity, usually in one eye, to a range of visual functions that cannot be corrected by refraction. Furthermore, binocular vision is reduced or absent.
Depth and extent of suppression is measured across the central visual field in healthy participants with monocularly blurred vision, healthy participants with monocularly reduced luminance using neutral density (ND) filters, and participants with naturally disrupted binocular vision and/or amblyopia. Suppression of spatial stimuli defined by luminance (L) and luminancemodulated noise (LM) was compared to that measured for stimuli defined by contrast-modulated noise (CM), for which there is no change in mean luminance. For all stimuli suppression depth increased with increased imbalance of binocular input. Suppression was of a similar depth across the visual field with imposed blur and localised central suppression was found with ND filters. Microstrabismics showed central suppression, while strabismic amblyopes showed central in addition to hemifield suppression.
Suppression for all participants was measured to be deeper for CM spatial stimuli than for LM spatial stimuli. This is suggested to be a result of CM stimuli engaging more binocular mechanisms of processing, than LM stimuli, thereby becoming more sensitive to disruptions of binocularity such as those produced in the participants in the present study. CM stimuli are therefore more sensitive to detecting suppression, which is associated with amblyopia.
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Chima, Akash S. "Neural mapping of binocular and amblyopic suppression." Thesis, Anglia Ruskin University, 2015. http://arro.anglia.ac.uk/581521/.
Full textAbstract:
Inter-ocular suppression occurs when very different images are presented to each eye. Diplopia ensues if different images are superimposed and perceived. The brain removes this unfavourable viewing experience by suppressing one eye’s input to enable clear single vision. Inter-ocular suppression during visual development occurs in response to sufficiently disparate images caused by strabismus (misalignment of the visual axis) or anisometropia (uncorrected difference in refractive error), and if persistent may result in amblyopia. This is reduced visual sensitivity, usually in one eye, to a range of visual functions that cannot be corrected by refraction. Furthermore, binocular vision is reduced or absent. Depth and extent of suppression is measured across the central visual field in healthy participants with monocularly blurred vision, healthy participants with monocularly reduced luminance using neutral density (ND) filters, and participants with naturally disrupted binocular vision and/or amblyopia. Suppression of spatial stimuli defined by luminance (L) and luminancemodulated noise (LM) was compared to that measured for stimuli defined by contrast-modulated noise (CM), for which there is no change in mean luminance. For all stimuli suppression depth increased with increased imbalance of binocular input. Suppression was of a similar depth across the visual field with imposed blur and localised central suppression was found with ND filters. Microstrabismics showed central suppression, while strabismic amblyopes showed central in addition to hemifield suppression. Suppression for all participants was measured to be deeper for CM spatial stimuli than for LM spatial stimuli. This is suggested to be a result of CM stimuli engaging more binocular mechanisms of processing, than LM stimuli, thereby becoming more sensitive to disruptions of binocularity such as those produced in the participants in the present study. CM stimuli are therefore more sensitive to detecting suppression, which is associated with amblyopia.
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Goodyear, Bradley Gordon. "fMRI of human primary visual cortex at submillimeter resolution, ocular dominance and contrast perception in amblyopia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0001/NQ42523.pdf.
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Secen, John. "A functional MRI investigation into the neural correlates of the multiple-object tracking deficit in amblyopia." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27431.
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Amblyopia is a visual developmental disorder defined by reduced visual acuity in one (amblyopic) eye, while the other (fellow) eye has normal visual acuity and is otherwise healthy. Deficits in motion perception – such as multiple object tracking - affect both the amblyopic eye and the fellow eye. This thesis examined the neural correlates of the multiple-object tracking deficit to further understand the cortical deficit in amblyopia. Functional data were collected as participants with and without a history of amblyopia performed the multiple-object tracking task monocularly inside a 3T MRI scanner. Participants were asked to use their attention to track 0, 1, 2 or 4 of 9 moving balls (6 deg/s) for 12 seconds. MR signal change relative to fixation, as a function of target numerosity (track 0, track 1, track 2, track 4), group (control, amblyopia), and eye were examined in six regions of interest: putative V1, MT, superior parietal lobule, frontal eye fields, anterior intraparietal sulcus, and posterior intraparietal sulcus. For all four tracking conditions, area MT was found to be less active in participants with amblyopia with both fellow and amblyopic eye viewing. When tracking 4 balls, the anterior intraparietal sulcus was found to be less active in participants with amblyopia, only with amblyopic eye viewing. This finding suggests the functional differences in this region may be subtle. Future investigations targeting the network involved in sustained attention can determine the extent to which posterior parietal function may be impaired in amblyopia. Overall, this thesis provided neuroimaging evidence that the MT region is affected in human amblyopia, and that both eyes are affected by underlying cortical changes in dorsal extra-striate areas.
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Carlton, Jill. "The development of a paediatric disease-specific measure of health related quality of life in amblyopia." Thesis, University of Sheffield, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.684921.
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Ribeiro, Jaqueline Alves. "Development and functional assessment of natural latex membranes : a new proposal for the treatment of amblyopia." reponame:Repositório Institucional da UnB, 2016. http://repositorio.unb.br/handle/10482/22340.
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Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2016.Submitted by Fernanda Percia França (fernandafranca@bce.unb.br) on 2016-09-08T19:03:51Z No. of bitstreams: 1 2016_JaquelineAlvesRibeiro.pdf: 2612234 bytes, checksum: 1572b341382aba1a47d87ac82645b3c7 (MD5)
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O crescente desenvolvimento tecnológico e os avanços no campo da medicina permitiram uma significativa melhoria na qualidade de vida da população. Como por exemplo, desenvolvimento de biomateriais, que são empregados para substituir total ou parcialmente tecidos orgânicos perdidos ou danificados, ou mesmo serem utilizados em contato direto e contínuo com o corpo para realização de tratamento não farmacológico. A disfunção oftálmica ambliopia, também conhecido popularmente como olho preguiçoso, consiste na baixa de visão em um olho por não ter se desenvolvido adequadamente na infância. O objetivo desse trabalho foi a obtenção e caracterização de membranas de borracha natural a fim de avaliar sua viabilidade de aplicação como uma membrana oclusora com propriedade de alterar a passagem de luz e estimular o olho amblíope. Trata-se de uma nova proposta para tratamento de pacientes amblíopes utilizando membranas de látex. As membranas de látex foram confeccionadas pelas técnicas de deposição e a técnica criada denominada de Van Gogh sendo caracterizadas através de métodos físicos e químicos, a fim de analisar as propriedades do látex in natura e das membranas de borracha natural, tratadas termicamente a 40 e 70 °C. Os métodos utilizados para a caracterização das amostras foram: microscopia eletrônica de varredura (MEV), medidas de fluorescência, difração de raios X (XRD), análises termogravimétricas (TG), calorimetria exploratória diferencial (DSC), análise de absorção em soro fisiológico, espectroscopia por FT-IR modo ATR, análise de componentes principais e análise de passagem de luz. Na caracterização das membranas foram analisadas as propriedades dos polímeros com o intuito de se obter dados sobre a viabilidade do uso de uma membrana de látex LENCOC® no tratamento de ambliopia com segurança e conforto para o usuário. Foi possível verificar a passagem de luz das membranas de Van Gogh M1 e M2 com a oclusão parcial e total, respectivamente. Conclui-se que, os ensaios utilizados na caracterização da membrana de látex LENCOC® mostraram-se satisfatórios e promissores para sua utilização no tratamento da ambliopia.
The growing technological development and the advancements in the field of medicine caused significant improvement in the quality of life of the population. One example is the development of biomaterials, which are used to completely or partially replace parts of lost or damaged organic tissues and are also used in direct and continuous contact with the body in non-pharmacological treatments. Amblyopia, an ophthalmic disorder commonly known as lazy eye, result in decreased vision in one eye that does not develop properly during childhood. The objective of this study was to obtain and characterize natural rubber membranes in order to evaluate the feasibility of its application as an occluder membrane with the capacity of changing the course of light and stimulating the amblyopic eye. This is a new proposal for treating amblyopic patients using latex membranes. The latex membranes were produced with the deposition technique and a new technique called Van Gogh. They were characterized using physical and chemical methods in order to analyze the properties of latex in natura and of the natural rubber membranes, thermally treated at 40 °C and 70 °C. The methods used to characterize the samples were: scanning electron microscopy (SEM), Fluorescence measurements, X-ray diffraction (XRD), thermogravimetric analyses (TG), differential scanning calorimetry (DSC), saline absorption analysis, FT-IR spectroscopy ATR mode, principal component analysis (PCA) and light crossing analysis. When characterizing the membranes, we analyzed the properties of the polymers with the goal of obtaining data on the feasibility of using a LENCOC® latex membrane in the treatment of amblyopia with safety and comfort for the patient. The light crossing analysis of the M1 and M2 Van Gogh membranes presented partial and total occlusion, respectively. We concluded that the tests used for characterizing the LENCOC® latex membrane were satisfactory and promising regarding its use for the treatment of amblyopia.
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Salmon, Anne. "Higher-order aberrations in amblyopia : an analysis of pre- and post-wavefront-guided laser refractive correction." Thesis, Aston University, 2015. http://publications.aston.ac.uk/25159/.
Full textAbstract:
For more than a century it has been known that the eye is not a perfect optical system, but rather a system that suffers from aberrations beyond conventional prescriptive descriptions of defocus and astigmatism. Whereas traditional refraction attempts to describe the error of the eye with only two parameters, namely sphere and cylinder, measurements of wavefront aberrations depict the optical error with many more parameters. What remains questionable is the impact these additional parameters have on visual function. Some authors have argued that higher-order aberrations have a considerable effect on visual function and in certain cases this effect is significant enough to induce amblyopia. This has been referred to as ‘higher-order aberration-associated amblyopia’. In such cases, correction of higher-order aberrations would not restore visual function. Others have reported that patients with binocular asymmetric aberrations display an associated unilateral decrease in visual acuity and, if the decline in acuity results from the aberrations alone, such subjects may have been erroneously diagnosed as amblyopes. In these cases, correction of higher-order aberrations would restore visual function. This refractive entity has been termed ‘aberropia’. In order to investigate these hypotheses, the distribution of higher-order aberrations in strabismic, anisometropic and idiopathic amblyopes, and in a group of visual normals, was analysed both before and after wavefront-guided laser refractive correction. The results show: (i) there is no significant asymmetry in higher-order aberrations between amblyopic and fixing eyes prior to laser refractive treatment; (ii) the mean magnitude of higher-order aberrations is similar within the amblyopic and visually normal populations; (iii) a significant improvement in visual acuity can be realised for adult amblyopic patients utilising wavefront-guided laser refractive surgery and a modest increase in contrast sensitivity was observed for the amblyopic eye of anisometropes following treatment (iv) an overall trend towards increased higher-order aberrations following wavefront-guided laser refractive treatment was observed for both visually normal and amblyopic eyes. In conclusion, while the data do not provide any direct evidence for the concepts of either ‘aberropia’ or ‘higher-order aberration-associated amblyopia’, it is clear that gains in visual acuity and contrast sensitivity may be realised following laser refractive treatment of the amblyopic adult eye. Possible mechanisms by which these gains are realised are discussed.