There is considerable evidence to indicate that most gas permeable contact lenses do not transmit sufficient oxygen to supply all the corneal oxygen requirement. This problem is further exacerbated by non-valid methods of characterizing the oxygen performance of such lenses. The current methods of using oxygen permeability (Dk) and oxygen transmissibility (Dk/L) as indices of oxygen performance of contact lenses is completely erroneous. Dk and Dk/L pertain to contact lens materials in flat sheet form having uniform thickness and equal diffusion path at all points on the surface. Finished contact lenses, of necessity, are curved surfaces and of varying thickness. Consequently the concept of Dk and Dk/L cannot be applied to contact lenses. To date there are no studies to determine the absolute oxygen tension under gas permeable contact lenses on the human eye. All attempts to quantify the oxygen tension under a lens have been by indirect methods or by predicting the p02 from Dk values, using mathematical equations. These results do not match the clinical findings. This study was done to show that oxygen flux through a contact lens, measured in vitro, is a better determinant of the in vivo oxygen performance of gas permeable contact lenses. A special cell was designed to measure the oxygen flux, in vitro under standardised conditions. Contact lens microelectrodes were designed to measure the oxygen tension in vivo. The data obtainedwas used to develop a model for the oxygen performance of rigid gas permeable lenses on the human eye. / Thesis (M.Optom.)-University of Durban-Westville, 1989.

The effectiveness of a vision screening programme in government schools in the Durban Functional Region under the jurisdiction of the House of Representatives was evaluated. For the purpose of the study a Comprehensive Vision Screening Programme (CVSP) was developed based on the Modified Clinical Technique (MCT) used in the Orinda Study. Of the represetative sample of 419 children assessed, the CVSP classified 85 (20.3%) as referrals. In comparison, the school health nurses referred 35 (9.6%) of the children for a complete ocular examination, 40 per cent of which were unwarranted. Analysis of the usable records showed that the school vision screening programme (SVSP) correctly categorised 307 (83.9%) of the children and incorrectly categorised 59 (16.1%) of them. The latter consisted of 3.8% over-referrals and 12.3% under-referrals. The school vision screening programme did not detect with a reasonable degree of accuracy those children with visual disorders. The effectiveness of the SVSP, as determined by the phi coefficient, was 0.35. Approximately two thirds of the children with visual disorders were not detected by the SVSP. One in every eight children classified as having no visual problem by the SVSP was an under-referral and two in every five children referred by the SVSP were over-referred. The high incorrect referral rates was attributed to the use of inappropriate screening techniques. The prevalence of visual disorders in the children was 20.3%; in boys 18.7% and 21.9% in girls. The relative risk of visual disorders in girls compared to boys was 1.2 (95% CI = 0.8 - 1.7). The prevalence of eye co-ordination disorders was 11.2%, refractive error problems 10.3%, visual acuity 4.5%, perceptual status (colour vision and stereopsis) 4.0% and organic disorders 1.2%. The binocular disorders were characterised as convergence insufficiencies and the disorders of accommodation were described as accommodative insufficiencies. Referable myopia (6.7%) was more prevalent than referable hyperopia (2.1%). Myopia was more prevalent in girls and hyperopia was more prevalent in boys. The clinical findings of the refractive error was compared to that measured by an autorefractor. The findings were remarkably similar and the study concluded that the difference between the two measures was not clinically significant. The study recommended that the MCT be used as the method of choice in school vision screening protocols. / Thesis (M.A.)-University of Durban-Westville, 1992.

Age, sex, race, heredity, environment and nutrition have been found to influence ametropia. In this study, the distribution of refractive errors has been investigated in relation to age, sex, race, education and near work, and lighting conditions. Visual awareness and vision screening in pre-school and schoolchildren were also investigated. Data were collected using the Nikon auto-refractor, retinoscope, Snellen V.A chart, and subjective techniques. 777 people were refracted, whose ages ranged between four and eighty years. Measurements were made in different sections of Umlazi township, therefore people of different socio-economic sectors were refracted. Four year-old children were found to be hyperopic. Hyperopia decreased and refraction shifted towards emmetropia. Myopia started to appear at the age of ten. Myopia increased until the age of twenty, and thereafter decreased slowly until the age of thirty three, where the average refraction was emmetropia. From age forty onwards, hyperopia was predominant. The incidence of high astigmatism, high hyperopia and high myopia is low in this community. Most people fall in the spherical refractive error region of between -1.000 and +1.000. The curve is leptokurtotic with highest peak around +0.250. The cylindrical error is between -0.500 and -1.000. No significant difference between sexes was found except at the fourth age group (40-51), where females are more hyperopic than males. The other sex difference is at ages ten to twelve, where females develop myopia earlier than males. Illumination plays no important role in the development of refractive errors in this community. Education and near work seem to account very little to the development of myopia. The influence of heredity on the development of ametropia was not investigated in depth. However, there is no evidence of heredity influencing the development of ametropia. There is a lack of vision screening and visual awareness. / Thesis (M.Optom.)-University of Durban-Westville, 1988.

Aim: The aim of this study was to establish normal values for Schirmer tear test (version 2) and tear break up time (TBUT) in a South African young adult Black population. Method: Following ethical approval by the biomedical research and ethics committee, KwaZulu-Natal, participants were recruited from the city of Durban in South Africa via personal invitations, poster advertisements and University of KwaZulu-Natal optometry clinic clients. McMonnies questionnaire for dry eye diagnosis was administered and those who failed were excluded from the main study. Two hundred (100 males and 100 females) participants who met the inclusion criteria were included in the study. Following a slit lamp examination of the eye, the Schirmer test was administered and the following day, the TBUT was measured. A re-test version of the two procedures were conducted one week after, at about the same time of the day for each subject. Results: The participants were aged 18-30 years, mean = 20.77 ± 2.29 years. The mean Schirmer test values for all participants (N = 200; 400 eyes) was 15.96 ± 6.86mm. The values for the males and females (200 eyes each) were 16.34 ± 6.93mm and 15.58 ± 6.81mm respectively. The mean TBUT (400 eyes) was 7.18 ± 1.89 secs. The mean values for the males and females (200 eyes each) were 6.90 ± 1.88 secs and 7.32 ± 1.67 secs respectively. A strong positive correlation (r = 0.895) and (r = 0.914) respectively was found between the right and left eyes in the two tests. Conclusion: Generally, the mean values found in this study for the Schirmer test are similar to those that have been reported in the literature. However, values for TBUT differ from the values that have been previously reported, being higher in some instances and lower in others. These findings have implications for dry eye diagnosis and also contact lens practice in South Africa. / Thesis (M.Optom.)-University of KwaZulu-Natal, Westville, 2012.

Dyslexia is a neurological disorder with genetic origin that affects a person’s word processing ability, their spelling, writing, comprehension and reading, and results in poor academic performance. As a result, optometrists are consulted for assistance with the diagnosis and treatment of a possible vision condition. Optometrists are able to assist with treatment as part of a multidisciplinary management approach, where optometric support is necessary. International studies have indicated that up to 20% of Caucasian school children are affected by dyslexia, while there are no similar figures for African children. Studies have been done to assess the extent of visual defects among Caucasian dyslexics, but not among African dyslexic children. The aim of the study is therefore to determine the prevalence of vision conditions in an African South African population of dyslexic school children, and to investigate the relationship between dyslexia and vision. The possible relationship between dyslexia and vision conditions has been recognized as an important area of study, resulting in research being conducted in many countries. Studies have been undertaken by optometrists and ophthalmologists, who differ in their approach and attitude on how vision conditions affect dyslexia. A review of the literature revealed three broad areas of vision that may impact on reading ability, these being acuity defects, binocular vision and ocular pathology. Acuity defects consist of visual acuity and refractive error. Areas of binocular vision evaluated in the literature include near point convergence, heterophoria, strabismus, accommodative functions, vergence facility and reserves. Hyperopia was the only vision variable that was found to be consistently associated with difficulties with reading, but not causally while findings on other variables were inconclusive. However, all the studies acknowledged the complexity of the condition, and the need for a comprehensive multidisciplinary management approach for its diagnosis and management. The study was undertaken in the city of Durban, South Africa, using a case-control study of two groups of African school children between the ages of 10 and 15. Both study groups consisted of 31 children of normal intelligence, who were matched in gender, race and socio-economic status. The case group attended a school for children with learning disabilities, while the control group attended a mainstream school. At the time of the study, only one school catered for African children with learning disabilities, and only 31 of its pupils were diagnosed with dyslexia. Ethical approval was obtained from the University of KwaZulu-Natal; permission to undertake the study in the identified schools was obtained from the Department of Education, and the school principals consented on behalf of the learners, as it was not always possible to reach the individual parent. The researcher (an optometrist) visited both schools by appointment where rooms were made available to do the testing, and the tests were explained to all participants. The LogMar Acuity Charts were used to assess visual acuity, and static retinoscopy was used to assess refractive error. Binocular vision was tested using the cover test for ocular alignment, the Hirschberg test for strabismus, RAF rule for near point of convergence, ± 2 D flipper lenses for accommodation facilities, Donder’s push up methods, using the RAF rule for amplitude of accommodation, plus and minus lenses for relative accommodation, monocular estimation technique for accommodation posture, and prism bars for vergence reserves. Ocular pathology was assessed using a direct ophthalmoscope. The dyslexic group presented with the following: Refractive errors: hyperopia 6.5%, myopia 6.5%, astigmatism 10%, anisometropia 6.5%, remote near point of convergence 33%, esophoria at near 3%, exophoria at near 9.5%, accommodative infacility 54% and lag of accommodation 39.28%. The dyslexic group had relatively reduced fusional reserve compared to the control group. The control group presented with the following: Refractive errors: hyperopia 3%, astigmatism 13%, anisometropia 6.5%, remote near point of convergence 48%, esophoria at near 0%, exophoria at near 0%, accommodative infacility 33% and lag of accommodation 41.93%. The prevalence of a remote NPC was higher in the control group than in the dyslexic group and there was a statistically significant difference between the two groups: NPC break (p=0.049) and recovery (p=0.046). The prevalence of poor binocular accommodation facility at near was higher in the dyslexic group than in the control group and there was a statistically significant difference between the two groups (p = 0.027). Vision defects such as hyperopia, astigmatism, accommodation lag, convergence insufficiency, poor near point of convergence and accommodative infacility were present in the dyslexic pupils, but they were no more at risk of any particular vision condition than the control group. This study provided the prevalence of vision conditions in a population of African dyslexic children in South Africa, the only vision variable that was significantly more prevalent in the dyslexic population being the binocular accommodation facility at near, although the study was unable to find a relationship between dyslexia and vision. The statistically significant difference may not imply clinical significance due to the small sample size. However, it is recommended that any vision defects detected should be appropriately compensated for as defective vision can make reading more difficult for the dyslexic child. The sample size may have been a limitation; however, this was comparable with studies reviewed, most of which had sample sizes of less than 41. Due to the range of possible ocular conditions that could affect dyslexia, it is recommended that a larger sample size be used to ensure more conclusive results. Testing for relative accommodation with a phoropter would provide more accurate results, and accommodation facility and fusional reserves would be better assessed with suppression control. The study provides information and an indication of research needs regarding the prevalence of vision defects in an African South African population of dyslexic children. / Thesis (M.Optom.)-University of KwaZulu-Natal, Westville, 2010.

Background: Reading rate is a measure of fluency, reflecting the level of reading performance especially in children, which is not typically measured during routine eye examinations. Optometric clinical tests such as Snellen visual acuity are often poor predictors of everyday reading performance, as they test the smallest print a person is able to read rather than fluency. Conventional reading rate tests for educational purposes presents with many limitations; they concentrate on linguistic skills, increase in complexity as the reading progresses, limited by the readers vocabulary but more importantly, they do not take the level of the child's vision into consideration. There is currently no reading rate chart that is designed with optometric notations specifically for children with normal vision and low vision. It is therefore necessary to design a reading rate chart that takes the above limitations into consideration. Aim: This study aimed to design a chart that can be used to measure reading rates in normal sighted and low vision primary school children. Methods: The aim of the study was achieved in four parts; the design, reliability, validity of a reading rate chart and finally the testing of the chart on low vision participants. In the design of the chart, ten frequently used words in grade one English reading books were randomly selected from five primary schools in KwaZulu-Natal province, South Africa. The reliability and validity of the chart were established on normal sighted children, aged nine to twelve years from two primary schools in the Durban area chosen by convenience sampling method, with sample size of 100 for reliability and 100 for validity. Reliability was established with test and retest reading rates using the new chart while validity was established by determining the reading rates using new the chart and the Wilkins reading rate chart. Data were analyzed using the Paired t-test, Pearson correlation, and Bland and Altman method. Finally, the testing of the new chart without and with low vision device, on fourteen low vision children, aged eight to nineteen years, attending a school for the visually impaired in KwaZulu-Natal. Data was analyzed using Paired t-test and Pearson correlation. Results: The words were arranged in random order, ten words per row and ten rows per paragraph. The chart consisted of six paragraphs (versions A, B, C, D, E and F) with six acuity levels and four optometric notations. Each version was printed on a separate sheet, in Arial and Times New Romans fonts and printed in black ink on approximately white cardboards. In reliability, the mean test and retest reading rates were 77.65 ± 25.30 and 78.23 ± 24.70 (p = 0.29, R² = 0.95). In Bland and Altman method, the mean difference was −0.58 with confidence limits at +10.07 and -11.23. In validity, reading rate for Wilkins chart and the new chart were 75.82 ± 23.64 and 74.92 ± 23.58 (p = 0.01, R² = 0.99) respectively. In Bland-Altman method, the mean difference was +0.90, upper limit at +6.33 and lower limit at –4.53. The mean reading rate, of the low vision children, without and with the low vision device were 59.32 ± 24.08 words per minute (wpm) and 67.04 ± 25.63 words per minute (wpm) respectively (p = 0.09 and r = 0.82). Conclusions: This chart can be used for reading rate assessment for both normally sighted and low vision children and is statistically reliable and valid. / Thesis (M.Optom.)-University of KwaZulu-Natal, Westville, 2012.

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.