Dissertations / Theses on the topic 'Clinical optometry'

This thesis sets out to examine in detail the condition of systemic hypertension (high Blood Pressure) in relation to optometric practice in the United Kingdom. Systemic hypertension, which is asymptomatic in the early stages, is diagnosed from the Blood Pressure (BP) measurement recorded by a sphygmomanometer and/or from the complications that have developed in target organs. Optometric practice based surveys revealed that diagnosed systemic hypertension was the most prevalent cardiovascular medical condition (20.5%). Measurement of BP of patients in this sample revealed that if an optometrist included sphygmomanometry into the sight examination then at least one patient each day would be referred for suspect systemic hypertension. Optometric opinion felt that the measurement of BP in optometric practice would advance the profession, being appreciated by both patients and General Practitioners (GPs), but was felt to be an unnecessary routine procedure. The present sight examination for the systemic hypertensive is similar to that of the normotensive patient, but may involve an altered fundus examination and a visual field test. The GPs were in favour of optometric BP measurement and a future role in the share care management of the systemic hypertensive. The application of a new pictorial grading scale for the grading of vascular changes associated with pre-malignant systemic hypertension was found to be both accurate and reliable. Clinical trial of the grading scale in optometric practice found positive correlations between BP and increasing severity of the retinal vascular features. The application of the pictorial grading scale to optometric practice and training the optometrist in the use of sphygmomanometry would improve the management of the systemic hypertensive patient in optometric practice. Future advances in image analysis hold substantial benefits for the detection and monitoring of subtle vascular changes associated with systemic hypertension.

Visual perception is dependent on both light transmission through the eye and neuronal conduction through the visual pathway. Advances in clinical diagnostics and treatment modalities over recent years have increased the opportunities to improve the optical path and retinal image quality. Higher order aberrations and retinal straylight are two major factors that influence light transmission through the eye and ultimately, visual outcome. Recent technological advancements have brought these important factors into the clinical domain, however the potential applications of these tools and considerations regarding interpretation of data are much underestimated. The purpose of this thesis was to validate and optimise wavefront analysers and a new clinical tool for the objective evaluation of intraocular scatter. The application of these methods in a clinical setting involving a range of conditions was also explored. The work was divided into two principal sections: 1. Wavefront Aberrometry: optimisation, validation and clinical application The main findings of this work were: • Observer manipulation of the aberrometer increases variability by a factor of 3. • Ocular misalignment can profoundly affect reliability, notably for off-axis aberrations. • Aberrations measured with wavefront analysers using different principles are not interchangeable, with poor relationships and significant differences between values. • Instrument myopia of around 0.30D is induced when performing wavefront analysis in non-cyclopleged eyes; values can be as high as 3D, being higher as the baseline level of myopia decreases. Associated accommodation changes may result in relevant changes to the aberration profile, particularly with respect to spherical aberration. • Young adult healthy Caucasian eyes have significantly more spherical aberration than Asian eyes when matched for age, gender, axial length and refractive error. Axial length is significantly correlated with most components of the aberration profile. 2. Intraocular light scatter: Evaluation of subjective measures and validation and application of a new objective method utilising clinically derived wavefront patterns. The main findings of this work were: • Subjective measures of clinical straylight are highly repeatable. Three measurements are suggested as the optimum number for increased reliability. • Significant differences in straylight values were found for contact lenses designed for contrast enhancement compared to clear lenses of the same design and material specifications. Specifically, grey/green tints induced significantly higher values of retinal straylight. • Wavefront patterns from a commercial Hartmann-Shack device can be used to obtain objective measures of scatter and are well correlated with subjective straylight values. • Perceived retinal stray light was similar in groups of patients implanted with monofocal and multi focal intraocular lenses. Correlation between objective and subjective measurements of scatter is poor, possibly due to different illumination conditions between the testing procedures, or a neural component which may alter with age. Careful acquisition results in highly reproducible in vivo measures of higher order aberrations; however, data from different devices are not interchangeable which brings the accuracy of measurement into question. Objective measures of intraocular straylight can be derived from clinical aberrometry and may be of great diagnostic and management importance in the future.

The two elcctrophysiological tests currently favoured in the clinical measurement of hearing threshold arc the brainstorm evoked potential (BAEP) and the slow vertex response (SVR). However, both tests possess disadvantages. The BAEP is the test of choice in younger patients as it is stable at all levels of arousal, but little information has been obtained to date at a range of frequencies. The SVR is frequency specific but is unreliable in certain adult subjects and is unstable during sleep or in young children. These deficiencies have prompted research into a third group of potentials, the middle latency response (MLR) and the 40HZ responses. This research has compared the SVR and 40HZ response in waking adults and reports that the 40HZ test can provide a viable alternative to the SVR provided that a high degree of subject relaxation is ensured. A second study examined the morphology of the MLR and 40HZ during sleep. This work suggested that these potentials arc markedly different during sleep and that methodological factors have been responsible for masking these changes in previous studies. The clinical possibilities of tone pip BAEPs were then examined as these components were proved to be the only stable responses present in sleep. It was found that threshold estimates to SOOHz, lOOOHz and 4000Hz stimuli could be made to within 15dBSL in most cases. A final study looked more closely at methods of obtaining frequency specific information in sleeping subjects. Threshold estimates were made using established BAEP parameters and this was compared to a 40HZ procedure which recorded a series of BAEPs over a 100msec. time sweep. Results indicated that the 40mHz procedure was superior to existing techniques in estimating threshold to low frequency stimuli. This research has confirmed a role for the MLR and 40Hz response as alternative measures of hearing capability in waking subjects and proposes that the 40Hz technique is useful in measuring frequency specific thresholds although the responses recorded derive primarily from the brainstcm.

Purpose. It has been documented previously that the push up (PU) and pull away (PA) methods overestimate accommodative amplitude (AA), while the minus lens-to-blur (MLB) method underestimates it. It also has been shown that the PU and PA methods produce similar results. We sought to compare data obtained from these three clinically used methods to determine AA in children and young adults with base-line normative data predicted by Hofstetter. Methods. Ninety healthy subjects (mean 11.7 years, range: 6-36 and 50F/40M), split into two groups, children (mean 9.8 years, range: 6-13 and 38F/22M) and young adults (mean 25.5 years, range: 21-36 and 16F/14M), were recruited from the patient and student populations of two schools of optometry. The subjects completed three accommodative tests presented in a random order: PA, PU, and MLB methods. Results.Findings from the MLB technique varied significantly from Hofstetter's normative values (P Conclusions. As compared with Hofstetter's normative values, this study demonstrates that the MLB technique gives a lower AA in children, while the PU and PA methods yielded consistent findings with each other and with Hofstetter's normative values. The PU method yielded values that compared closest with Hofstetter's normative data for the oldest subjects 4 tested in this study and indicates that the most consistent methods to measure AA in children is either the PU or PA methods, and the PU method for adults.

This study was designed to compare computer aided learning (CAL), in the form of a Virtual Patient (VP), and traditional didactic lectures as methods of teaching clinical decision making (CDM) skills to second year Optometry undergraduates. Comparisons were based on performance in multiple-choice examinations testing CDM skills (actual mastery), student feedback relating to confidence in CDM skills (perceived mastery or self-efficacy) and student satisfaction. The influence of sex, learning style and academic ability was also investigated. This is the first time that these aspects of teaching pedagogy have been studied together. Current literature informed development of didactic lectures and an online VP. Both teaching methods were designed to ensure that the same clinical content was included. This content was aimed at training students to perform problem-orientated eye examinations. A cohort of 102 students was taught using the traditional didactic lectures in academic year 2010-11 and 93 students using the online VP in academic year 2011-12. An established Index of Learning Styles instrument was used to classify students according to their preference in four learning style dimensions. Both teaching methods were designed to cater for both poles of each learning style dimension. Most students had no strong learning preferences but those that did had a tendency towards the active-sensing-visual-sequential profile. Actual and perceived mastery were scored for five key learning objectives; question selection, critical symptom recognition, test selection, critical sign recognition and referral urgency selection. The influence of academic ability and teaching method differed for each learning objective; didactic lectures favouring some, the VP others. Learning style and sex had no influence, indicating that both teaching methods catered equally for males and females with all learning styles. Comparisons between perceived and actual mastery revealed poor self-assessment accuracy. Student satisfaction, rated on a five point Likert scale, was equally high for both teaching methods. Sex was the only influential variable, with males favouring one aspect of VP training. Overall, the findings suggest that CAL should be used to supplement traditional teaching rather than replace it in order to ensure that all students benefit equally. Future research may wish to focus on self-assessment accuracy as a means of improving academic performance.

Although experiential prescribing maxims are quoted in some optometric textbooks their content varies significantly and no direct research evidence was available to support their use. Accordingly in chapters 2 and 3, the uses of several potential prescribing rules were investigated in the UK optometric profession. Our results indicated that the subjective refraction result exerted a strong hold on the prescribing outcome with 40-85% of optometrists prescribing the subjective result in a variety of scenarios. The finding that after 40 years qualified, experienced optometrists were three times more likely to suggest a partial prescription was an important discovery that provides significant support for the prescribing rules suggested by various authors. It would also appear from the results of the retrospective evaluation of the ¿if it ain¿t broke, don¿t fix it¿ clinical maxim in Chapter 4 that spectacle dissatisfaction rates could be reduced by between 22 to 42% depending on how strictly the maxim is interpreted by the practitioner. Certainly an ¿if it ain¿t broke, don¿t fix it much¿ maxim was suggested as being particularly appropriate. Chapter 5 included a reanalysis of previously published data that found no change in falls rate after cataract surgery to investigate any influence of refractive correction change and /or visual acuity change on falls rate. Unfortunately these data were not sufficiently powered to provide significant results. In chapter 6, a spectacle adaptation questionnaire (SAQ) was developed and validated using Rasch analysis. Initial studies found no differences in SAQ with gender or age.
College of Optometrists

Although experiential prescribing maxims are quoted in some optometric textbooks their content varies significantly and no direct research evidence was available to support their use. Accordingly in chapters 2 and 3, the uses of several potential prescribing rules were investigated in the UK optometric profession. Our results indicated that the subjective refraction result exerted a strong hold on the prescribing outcome with 40-85% of optometrists prescribing the subjective result in a variety of scenarios. The finding that after 40 years qualified, experienced optometrists were three times more likely to suggest a partial prescription was an important discovery that provides significant support for the prescribing rules suggested by various authors. It would also appear from the results of the retrospective evaluation of the 'if it ain't broke, don't fix it' clinical maxim in Chapter 4 that spectacle dissatisfaction rates could be reduced by between 22 to 42% depending on how strictly the maxim is interpreted by the practitioner. Certainly an 'if it ain't broke, don't fix it much' maxim was suggested as being particularly appropriate. Chapter 5 included a reanalysis of previously published data that found no change in falls rate after cataract surgery to investigate any influence of refractive correction change and /or visual acuity change on falls rate. Unfortunately these data were not sufficiently powered to provide significant results. In chapter 6, a spectacle adaptation questionnaire (SAQ) was developed and validated using Rasch analysis. Initial studies found no differences in SAQ with gender or age.

A sizeable amount of the testing in eye care, requires either the identification of targets such as letters to assess functional vision, or the subjective evaluation of imagery by an examiner. Computers can render a variety of different targets on their monitors and can be used to store and analyse ophthalmic images. However, existing computing hardware tends to be large, screen resolutions are often too low, and objective assessments of ophthalmic images unreliable. Recent advances in mobile computing hardware and computer-vision systems can be used to enhance clinical testing in optometry. High resolution touch screens embedded in mobile devices, can render targets at a wide variety of distances and can be used to record and respond to patient responses, automating testing methods. This has opened up new opportunities in computerised near vision testing. Equally, new image processing techniques can be used to increase the validity and reliability of objective computer vision systems. Three novel apps for assessing reading speed, contrast sensitivity and amplitude of accommodation were created by the author to demonstrate the potential of mobile computing to enhance clinical measurement. The reading speed app could present sentences effectively, control illumination and automate the testing procedure for reading speed assessment. Meanwhile the contrast sensitivity app made use of a bit stealing technique and swept frequency target, to rapidly assess a patient’s full contrast sensitivity function at both near and far distances. Finally, customised electronic hardware was created and interfaced to an app on a smartphone device to allow free space amplitude of accommodation measurement. A new geometrical model of the tear film and a ray tracing simulation of a Placido disc topographer were produced to provide insights on the effect of tear film breakdown on ophthalmic images. Furthermore, a new computer vision system, that used a novel eye-lash segmentation technique, was created to demonstrate the potential of computer vision systems for the clinical assessment of tear stability. Studies undertaken by the author to assess the validity and repeatability of the novel apps, found that their repeatability was comparable to, or better, than existing clinical methods for reading speed and contrast sensitivity assessment. Furthermore, the apps offered reduced examination times in comparison to their paper based equivalents. The reading speed and amplitude of accommodation apps correlated highly with existing methods of assessment supporting their validity. Their still remains questions over the validity of using a swept frequency sine-wave target to assess patient’s contrast sensitivity functions as no clinical test provides the range of spatial frequencies and contrasts, nor equivalent assessment at distance and near. A validation study of the new computer vision system found that the authors tear metric correlated better with existing subjective measures of tear film stability than those of a competing computer-vision system. However, repeatability was poor in comparison to the subjective measures due to eye lash interference. The new mobile apps, computer vision system, and studies outlined in this thesis provide further insight into the potential of applying mobile and image processing technology to enhance clinical testing by eye care professionals.

Background: The World Health Organization estimates that there are 517 million people in the world who are visually impaired due to uncorrected presbyopia. Equal sphere ready-made bifocal and single vision reading spectacles are an inexpensive alternative to custom made spectacles. Methods: A visual satisfaction questionnaire was administered before patients were examined at an outreach clinic and again after ready-made bifocals or reading spectacles were dispensed. The results of both sets of questions along with presenting acuities, corrected acuities, refractive data, and willingness to pay were analyzed. Results: There was an unmet need of 38% (of the 338 subjects that needed glasses only 208 had them). There was no gender bias; the unmet need was higher in the rural areas (47% rural, 36% urban). Those who could not read were 3.4 times less likely to have the glasses they needed than the literate. Unmet need decreased with every level of education. Those without any schooling showed 77% prevalence of unmet need and those with university education had an unmet need rate of 32%. Ready-made spectacles were dispensed to 89.5% of those examined. The ready-made bifocals were very well accepted, with the percentage of subjects giving the highest satisfaction rating improving from a presenting value of 11% to 89.4% with the bifocals at distance and from 6.6% to 89.4% at near. Distance visual acuity of 20/40 or better improved from the presenting value of 60% to 84.5% and near vision of 20/40 or better improved from the presenting value of 44% to 97%. With ready-made single vision readers, functionally good near vision (20/40 or better) improved from a presenting value of 38% to 97%. The highest ranking for near satisfaction improved from 6.3% to 86.6%. The subjects indicted that they would be willing to pay US$18.39 to replace the bifocals and US$16.67 to replace the readers. Conclusion: There is a high unmet need for vision correction in the population over age 35 in Nicaragua. Dissatisfaction with distance and near vision is very high. Although custom made glasses are ideal, ready-made bifocals and ready-made single vision readers are an acceptable and affordable alternative.

This is a study on the prevalence of refractive errors and patients requiring refractive services at 15 eye clinics in the Amathole, Chris Hani, Joe Gqabi and OR Tambo District Municipalities of the Eastern Cape. This is an area characterised by extreme poverty where the cost of an eye examination and prescription spectacles remains financially unobtainable for most. Optometry services are provided mainly by private optometrists who service the small proportion of the population that can afford them. Adults and children remain house bound or are labelled as dull and unproductive simply because they don’t have access to an eye examination and a pair of spectacles. Purpose The purpose of the study is to identify patients with refractive errors and those requiring refractive services at the 15 eye clinics in the Eastern Cape. Another purpose is to describe the refractive services that are available to patients attending health facilities, where the eye clinics are conducted. Lastly, the purpose is to explore the possibility of nurses providing refractive services independently or under the supervision of optometrists to supplement the lack to refracting and dispensing services. Study Method A quantitative and qualitative non-experimental descriptive design was used. Research involved the analysis of Vision Care’s eye clinic records collected from 15 eye clinics from January 2010-June 2010. Semi-structured interviews were conducted with 30 nurses working at the 15 health facilities where the eye clinics were conducted using purposive sampling. The quantitative data was analysed using excel spreadsheets and graphs and qualitative data was analysed using coding and categorizing methods. Conclusion According to Vision Care’s data of the patients assessed, 19.2 percent had a refractive error and 54 percent of the patients required refractive services. It is estimated that 71.41 percent of the patients had a refractive error according to the optometrist. Although there were some organisations active in the eradication of cataracts, there was little healthcare available in the form of refraction services. xiv Patients needed to travel an average of 63.8kms to access refraction services against the backdrop of poor roads, poverty and unemployment. 28 out of 30 nurses either ‘strongly agreed’ or ‘agreed’ that nurses could be trained to perform refractions and dispense spectacles. 29 out of 30 nurses thought that this would have a positive impact on eye care. Further research is necessary to assess the feasibility of implementing a nurse operated refractive program and whether it should be within their scope of practice to refract and dispense spectacles.

碩士
中山醫學大學
生物醫學科學學系碩士班
100
Refraction errors are commonly found in clinical settings and are the most avoidable among all the factors that may affect vision. Previous researches have pointed out that pinhole can be used for the best correction of refraction errors. However, the use of pinhole to achieve best corrected visual acuity (BCVA) has not been extensively studied under different illumination conditions. This study aims to clarify this issue in an effort to achieve the best use of pinhole. A total of 30 volunteers, aged between 20 and 50, were recruited to assess visual acuity under 500 lux or 5 lux conditions, with black target or white target. The results were analyzed with student’s T test and Paired-T test. The average visual acuity achieved with white target under 5 lux was 0.63 ± 0.20 without pinhole, which was increased to 0.81 ± 0.23, showing a relative increase by 8.82% ± 48.43 ( p < 0.001 ). Furthermore, the results indicated that pinhole with white target under 5 lux may be used for prediction of whether BCVA had been achieved by the previous prescription. Thus, a novel use of pinhole was proposed.

In a teaching clinic, healthcare students and their supervisors talk with their patients in the examination room and they talk about their patients during teaching consultations outside the examination room. Effective doctor-patient communication helps to establish management plans that are appropriate for both doctors and their patients. Amid a pressure to provide more patient-centered care, communicating effectively with older adult patients is particularly crucial because the occurrence of health problems and the likelihood of age-based communication barriers and negative attitudes increase with age. This project is a qualitative, collective case study of eye examinations, case presentations and participant interviews. This study took place in the Primary Care Clinic at the University of Waterloo, School of Optometry. Participants included 8 fourth-year optometry students, 5 supervising optometrists, and 10 patients between 60 and 85 years of age. The study involved audio-recording and analyzing eye examinations of older adult patients, case discussions about these patients, and interviews of older adult patients, optometry students and their optometrist supervisors. Data were analyzed using a constant-comparative approach, consistent with grounded theory. This study identified some of the discursive features of and reflections about patient-centered communication during the talk with and about older adult patients. During the eye examinations, optometry students incorporated five types of verbal communication that were consistent with a patient-centered model: Patient Agenda, Social Talk, Analogies, Patient Agency, and Health Promotion & Prevention. Although these successful attempts to incorporate patient-centered communication strategies were evident in the talk with patients, optometry students routinely engaged in seven other verbal strategies that challenged this patient-centered ethos: Closed-Ended Questions, Biomedical and Technical Language, Patient as a Problem, Unacknowledged Patient Voice, Patient Understanding, Doc Talk, and Caregiver Agency. Two types of discursive strategies related to patient-centered care were identified in the talk about older adult patients during novice case presentations: Voice of Optometry and Voice of Patient. The Voice of Optometry incorporated field-sanctioned language strategies including three subcategories: Biomedical, Technical and Judgment. In contrast, the Voice of Patient represented various levels of patient agency: Passive Recipient, Negotiated Agency and Patient Agency. According to their interviews, optometry students received limited explicit training, in both classroom and clinic instruction, on how to talk with and about patients. During their interviews, optometry students and their supervisors made clear distinctions between patient–centered and doctor-centered care. Most of the students and supervisors believed that the optometry profession and the optometry school promoted patient-centered care. Elements of patient voice were represented in the eye examinations, the case presentations and the post-examination patient interviews. During novice case presentations patient voice was often fragmented into sound bytes of the original patient statements or translated into field-sanctioned language. Although many instances of patient education and counselling were evident throughout the eye exams, limited discussion occurred in the novice case presentations between students and their instructors about what to say to patients, In addition, the majority of topics addressed during educational and counselling moments were not discussed during the novice case presentations. Additionally, post-examination patient recall regarding education and counselling was generally limited. Throughout this study, talk about age appeared in four ways: 1) caregivers used age to make clinical decisions during case presentations, 2) caregivers referenced age during counseling and education to explain eye and vision changes, 3) patients commented on the impact of age on themselves, and 4) caregivers spoke about how they considered age when speaking to their patients. While the caregivers generally valued a patient-centered approach, the talk with and about patients was skewed towards strategies that may limit the ability to support this ethos. It is questionable what audience (i.e. patient or supervisor) optometry students value and how this affects their ability to adopt patient-centered communication strategies. Findings from this study suggest that caregivers and their patients might benefit from some changes in the way patient-centered practice is taught and practiced in this optometry teaching clinic. As a greater understanding develops of the strategies of and challenges to patient-centered practices in optometry, it is my hope that optometry training programs as well as optometry professional organizations will further embrace patient-centered practices.

M.Sc. (Optometry)
The difference between objective automatic and subjective clinical refraction is studied using new statistical techniques. The question, by how much the two refraction techniques differ, is investigated by subtracting the subjective refraction finding from the auto refractory finding and then examining the distribution of the difference or excess as it will be called here. Computerized procedures were developed to automate mathematical and statistical methods of analysis. The methods were applied to two different samples: one of patients visiting an ordinary optometric practice (the clinical sample) and the other of children refracted in a screening program (the sample of school children) . The clinical sample, consisting of mainly older patients, is examined first. The difference between the autorefractor and subjective findings is studied and described. This difference could be used to compare different types of auto refractors assuming that the subjective refraction is correct. For the purpose of this study, however, the results of eight autorefractors are grouped together, combining left and right eyes, to serve as basis for studying the older population. The study shows that on the average there is no clinically significant excess. This means that there is on average no clinically significant difference between the automatic and clinical refraction for this population.