Many individuals with impaired vision experience a decreased quality of life. Quality of life is defined as "the degree to which an individual enjoys the important possibilities of their life. " Vision rehabilitation outcomes primarily focus on the functional impacts of interventions, with less attention being paid to any associated psychosocial impacts. This study examines the relationship between measures of visual function status and psychosocial status in individuals acquiring low vision assistive devices for the first time. One hundred and twenty subjects were evaluated after purchasing their first low vision device from a University-based low vision clinic. The measures used were the National Eye Institute Visual Function Questionnaire (NEI-VFQ 25) and the Psychosocial Impact of Assistive Devices Scales (PIADS). The NEI-VFQ 25 measures the status of visual function, while PIADS is a device impact measure, which explores the psychosocial impact of devices on three domains: competence, adaptability, and self-esteem. This study determines the strength of association between these two measures at initial and follow-up administrations, and between each subsequent measure as a result of the time interval between administrations, in addition to assessing whether or not a change in stability for the measures occurred over time. Modest strengths of associations were anticipated and the short time interval was not expected to be a factor in change in stability of the measures. The expectation was that subjective reports of functional changes should have a moderate correlation with psychosocial impact.

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.

The aim of this study was to determine management regimens and level of knowledge of diabetes and its‟ ocular complications among private patients in a sample of the population of the Western Cape region of South Africa. A population-based cross-sectional study design, using purposive accidental random sampling, was used. Questionnaires completed by diabetic patients who fund their condition privately outside of the South African Public Health sector were used. One hundred and twenty-two subjects participated in the research, 66 (54%) males and 56 (46%) females. There were 73 rural and 49 urban participants. The overall sample mean BMI was 30.7, average fasting plasma glucose (FPG) 8.1 mmol/l and the majority of respondents did not perform a daily FPG test or know the significance of the HbA1c test. The majority of participants were unaware of the serious ocular consequences of prolonged hyperglycaemia. Sixty-seven percent of respondents considered that they knew enough about diabetes to manage their own condition. From the data it is apparent that private patients‟ knowledge of the systemic and ocular complications of diabetes is sub-optimal. Whilst the majority considered annual eye examinations as important, less than one-third of respondents actually undertook them. Optometrists should be offered programmes to enhance their skills and co-manage and educate diabetic patients with other health care practitioners on a formal basis. Health insurance institutions should take cognisance of the value of patient education and preventative diabetic management and incentivize patients and health care providers in this regard. / Thesis (M.Optom.)-University of KwaZulu-Natal, Westville, 2011.

The 2010 National Education Technology Plan steadily replaces paper textbooks with study materials on computers. One risk of increased computer usage is increased Computer Vision Syndrome (CVS) symptoms. I researched multiple studies to analyze the effects of computer use on dry eye and eye strain and how these symptoms can progress to musculoskeletal pain, headaches, decreased quality of life, loss of confidence and even anxiety and depression. Currently, there is not much data on tablet use so I propose two future experiments to determine if tablets can also cause CVS ocular symptoms.

Myopia is a major cause of vision loss throughout the world. High myopia is associated with severe eye diseases like maculopathy, retinal detachment and glaucoma. The prevalence of myopia is increasing, and varies by country and by ethnic group. In some Asian populations the prevalence is 70%-80%.  This thesis includes five experiments. In experiment I we investigated the effects of added positive and negative spherical aberration on accommodative response accuracy. We found that the accommodative response can be altered by modulating the spherical aberration of the eye with soft contact lenses. There was an improvement in the accommodative response slopes and a decrease in the lag of accommodation with the negative spherical aberration lenses compared to positive spherical aberration lenses.  In experiment II we investigated whether the negative spherical aberration in contact lenses could be tolerated visually in terms of wearability and comfort. We found that all the subjects were satisfied with the contact lens comfort, distance and near vision and the stability of the vision with the lenses. The accommodative response was stable through out the treatment period. In experiment III we investigated the efficacy of a novel dual treatment for the improvement of accommodative accuracy and dynamics in myopes. The spherical aberration of the eye was effectively altered to negative in the treatment group as predicted. In the control group as expected there was no significant change in the spherical aberration of the eye with and without contact lenses. The treatment lenses decreased the lag of accommodation and increased the accommodative response slope at 3 months. In the experiment IV we investigated the effect of the treatment lenses used in the previous experiment on high and low contrast visual acuities after a one year treatment period. The results showed a significant improvement in both high and low contrast visual acuities after the one year period in the treatment group compared to the control group, even though it was not clinically significant. In experiment V we investigated the intrasession repeatability of peripheral aberrations using COAS-HD VR aberrometer and also reported the distribution of higher order aberrations in a group of young emmetropes. There was no significant difference in the variance of total higher-order RMS between on- and off-axis measurements. There was a significant change in the horizontal coma, spherical aberration and higher-order RMS with off-axis angle along the horizontal visual field. We demonstrated that fast, repeatable and valid peripheral aberration measurements can be obtained with this instrument. This thesis contributes new results in this field of myopia, aberration and accommodation.

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.

Purpose: It is unknown whether individuals with two balanced eyes show quicker response and lower threshold in fine stereoscopic detection. Previous methods to measure ocular dominance were primarily qualitative, which do not quantify the degree of dominance and show limitation in identifying the dominant eye. In this study, we aimed at quantifying the difference of ocular strength between the two eyes with ocular dominance index (ODI) and studying the association of ocular balance between the two eyes with stereoscopic detection. Methods: Stereoscopic threshold was measured in thirty-three subjects. Stereopsis was measured with random dot stimuli. The minimal detectable disparity (Dmin) and the minimal time needed to acquire the best stereoacuity (Tmin) were quantified. Ocular dominance was measured by a continuous flashing technique with the tested eye viewing a titled Gabor patch increasing in contrast and the fellow non-tested eye viewing a Mondrian noise decreasing in contrast. The log ratio of Mondrian to Gabor’s contrasts was recorded when a subject just detected the tilting direction of the Gabor during each trial. The t-value derived from a t-test of the 50 values obtained in each eye was used to determine a subject’s ODI (ocular dominance index) to quantify the degree of ocular dominance. A subject with ODI ≥ 2 (p < 0.05) was defined to have clear dominance and the eye with larger mean ratio was the dominant eye. Results: The Dmin (55.40 arcsec) in subjects with two balanced eyes were not significantly different from the Dmin (43.29 arcsec) in subjects with clear ocular dominance (p = 0.87). Subjects with two balanced eyes had significantly (p = 0.01) shorter reaction times on average (Tmin = 138.28 msec) compared to subjects with clear dominance (Tmin = 1229.02 msec). Tmin values were highly correlated with ocular dominance (p = 0.0004). Conclusion: Subjects with two relatively balanced eyes take shorter reaction time to achieve optimal level of stereoacuity. Keywords: Ocular Dominance, Local Stereopsis, Binocular, Balanced Eyes, Anisometropia

Background. The United States military relies on visual acuity standards to assess enlistment induction and military occupational specialty eligibility. In addition, the military recently instituted the Vision Readiness and Classification System to monitor Soldiers' combat vision readiness. The primary aim of this study was to investigate the relationship between visual acuity and marksmanship performance using a single blind randomized trial with the Engagement Skills Trainer 2000. Methods. Marksmanship performance was evaluated in 28 subjects under simulated day and night conditions with habitual spectacle prescription and contact lenses that created visual blur. Results. The relationship between visual acuity and marksmanship performance was found to have a statistically significant correlation of -0.735 with a 95% confidence interval from -0.790 to -0.669. Subsequently, 54 percent of the variance in marksmanship performance was accounted for by visual acuity. In addition, a panel poison regression model using an independent correlation structure revealed significant differences (p< .001) as visual acuity decreased from 20/25 to 20/50. Conclusions. Marksmanship performance decreases as visual acuity decreases. This relationship supports the use of a visual acuity requirement in the assessment of military readiness.

Objectives: This study compares wearing time for four months after receiving a new spectacle correction in subjects within Autism Spectrum Disorder (ASD) population to typically developing (TD) children and adolescents age 9 to 17 years old. Methods: Children and adolescents who were ASD or TD were enrolled from subjects recruited from another pilot study focused on eye examination testing for children and adolescents with ASD. A psychologist determined group status/ eligibility using American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-Text Revision (DSM-IV-TR) criteria after review of previous evaluations and parent report of symptomology on the Social Communication Questionnaire. Parents provided the subject's age, level of parent education, gender, race, ethnicity and urbanization level. Parents completed a telephone survey at 1, 2, 4, 8, 12, and 16 weeks after the child received their spectacles. The survey asked questions about wearing time, willingness to wear spectacles and amount of prompting required. Data was analyzed to determine if there were differences between the ASD and TD group. Results: 22 subjects were enrolled who met review criteria for ASD or TD group and needed refractive correction. No significant difference was found between ASD and TD wearing time (p > 0.05). Age, gender, ethnicity, level of parent education, urbanization level and grade in school did not demonstrate differences in adaptation between the TD and ASD groups. Conclusions: Parental reports of wearing time and resistant behavior demonstrate that children and adolescents with ASD adapt to spectacle wear for significant refractive error similarly to typical children and adolescents.

ABSTRACT Global summation of radial frequency patterns and the effect of sudden onset glare on shape discrimination The purpose of this study was to provide evidence of global pooling around the circumference of the Radial frequency (RF) pattern, and to study the effect of sudden onset glare on shape discrimination. The RF stimuli were generated by the amplitude modulation of the radius of a circle which deforms them from circularity, while the cross sectional luminance profile was the fourth derivative of Gaussians (D4). The amplitude of the stimuli determines how distinct the pattern is and thus measures the degree of sensitivity while the radial frequency determines the number of lobes the pattern has. In the first part of the study, whole RF patterns (RF3 to RF16) and open component fractions (0.125, 0.25, 0.5, 0.75), which are incomplete sectors of the whole, were tested against their respective reference unmodulated patterns. Subjects were tasked with discriminating minute deviations from their reference patterns. In the second part of the study, high contrast (20 X detection threshold) RF3 and RF4 contours and equivalent low contrast (5 X detection threshold) RF3 and RF4 contours were used as stimuli. Shape discrimination threshold for the high contrast target was determined with and without sudden onset glare. The result of the first part of the study showed that threshold decreased significantly as larger component RF patterns were tested (p < 0.05). The decrease could not be accounted for by the probabilistic sampling of local filters (probability summation). The result of the second part of the study showed that shape discrimination threshold increased with sudden onset glare. The increase was even more pronounced with lower mean luminance and when smaller fractions of the contours were tested. Shape discrimination threshold was significantly higher with high contrast contours in the presence of glare than equivalent low contrast contours, indicating that the veiling luminance model alone could not account for a decrease in visual performance in this shape discrimination task.