The prevalence of aniridia and associated visual and ocular complications among learners in schools for the visually impaired in central South Africa
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Date
2020-07
Authors
Hatia, Sherazadh
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Publisher
University of the Free State
Abstract
Introduction Aniridia is a rare, sight-threatening ocular disorder characterised by partial or complete absence of the iris. It can affect multiple ocular structures and lead to visual complications. According to our knowledge, there is currently no recent published research on aniridia in the South African population, thus it would be beneficial to investigate the prevalence of aniridia and describe the ocular and visual complications in South Africa. Therefore, the aim of this research was to determine the prevalence of aniridia among learners in visually impaired schools in central South Africa (Free State and North West) and to describe its visual and ocular complications. In order to achieve the aim, the number of participants that had partial and complete aniridia was determined using an ophthalmoscope. Thereafter, the visual and ocular complications in participants with aniridia were determined. Methods A prospective descriptive study was conducted on learners in three visually impaired schools in central South Africa. A total of 117 consenting learners were screened with an ophthalmoscope to determine the presence or absence of aniridia and only the participants identified with aniridia were further examined. The visual acuity of the participants with aniridia was determined using a logMAR visual acuity chart, the refractive error was determined using an autorefractor, the intraocular pressure was measured using an iCare tonometer to determine the risk for glaucoma and the anterior and posterior segment of the eye was examined using a slit lamp, 90D lens and gonioscopy lens to determine the complications associated with aniridia. Results for each participant were recorded and participants who required further management were referred to the local Ophthalmology clinic. Data analysis was performed by the Department of Biostatistics (University of the Free State). Prevalence was calculated by dividing the number of participants with aniridia by the total number participants included in the study. Results Four participants were identified as having aniridia and thus the prevalence of aniridia was found to be 3,4% (4 out of 117). The ages of these participants were 10, 13, 17 and 20 years. Visual acuity for each eye individually ranged from no light perception to 0.86 logMAR (6/38). Corneal complications such as pannus, opacification and vascularisation were seen in all of the participants. Some form of cataract was seen in all four participants. The IOP ranged between 11mmHg and 19mmHg in 3 of the participants and was outside of the normal range (7mmHg – 21mmHg) in the 4th participant. Gonioscopy showed 75% of participants with grade 4 angles and the remaining participant with grade 2 angles. Cup-to-disc ratios varied between 0.5 and 0.8 with no glaucomatous changes. Foveal hypoplasia was present in 75% of participants and nystagmus was present in all of the participants. One participant presented with membrane-like structures in the posterior chamber of both eyes, making a view of the fundus unobtainable. Conclusion The prevalence found (3,4%) is representative of one school (Christiana School for the Blind in the North West) from the three that were included, not the whole of South Africa. Cataracts and nystagmus were the most prevalent ocular complications found in this group. The foveal hypoplasia and corneal abnormalities in conjunction with some form of cataract and nystagmus are all contributors to the reduced visual acuity observed in these participants. The findings from this study contribute to new information regarding aniridia in regions of central South Africa and enables the comparison of results with research conducted in other parts of the world. This research also provides information about the most recent prevalence of aniridia in this part of South Africa. Further research can be done in other parts of the country to support and add to these results.
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Keywords
Dissertation (M. Optometry (Optometry))--University of the Free State, 2020, Visually impaired - Schools - South Africa, Aniridia, Ophthalmologist