Abstract
Background: Oculocutaneous albinism results in defects of the visual pathway and ocular structures. Aim: To determine the ocular findings and vision status of learners with oculocutaneous albinism (OCA) as well as to establish the level of visual acuity, contrast sensitivity and reading rate improvements following optical correction. Setting: Three special education schools in KwaZulu-Natal, South Africa. Methods: A total of 81 learners with OCA participated in this study. Testing procedures included logMAR distance and near visual acuity (VA) measurements, cover tests, retinoscopy (dry), subjective refraction, tangent screen, ophthalmoscopy, contrast sensitivity and reading rate determination. Results: The majority of participants (96.3%) had wheat straw coloured hair and 95.1% had grey irides. All the learners presented with iris-transillumination and an absent foveal reflex and all but one exhibited nystagmus. Esophoria and esotropia represented 72.8% of binocular vision anomalies. Myopic astigmatism was noted in 41.4% of the learners while with the rule astigmatism was predominant (64%). Following optical correction, VA significantly improved from a range of 0.50 to 1.40 logMAR to a range of 0.5 to 1.06 logMAR for distance ( p 0.05). Conclusion: Learners with OCA exhibited various ocular and vision defects which impair visual functions. Their VA and contrast sensitivity could be significantly improved with optical correction; however, their reading rate was not improved.
Highlights
Albinism is an autosomal recessive disorder that results from a reduction of pigmentation in the structures of the skin and eyes.[1]
The classification of albinism is related to the affected genes, the most commonly affected ones being the tyrosinase gene on chromosome 11q14-21, which results in OCA1, and the P gene on chromosome 15q11.2, which results in OCA2
The prevalence of Oculocutaneous albinism (OCA) in Southern Africa has been reported to range between 0.02% and 0.1%, with a male to female ratio ranging from 0.8 to 1.4:1.5,6,7,8,9,10,11 Several eye and vision problems including ocular hypopigmentation, reduced visual acuity (VA), nystagmus, strabismus and photophobia are associated with albinism.[12]
Summary
Albinism is an autosomal recessive disorder that results from a reduction of pigmentation in the structures of the skin and eyes.[1] There are two main types of albinism: oculocutaneous and ocular. Oculocutaneous albinism (OCA) affects the optical system, skin and hair,[2] while ocular albinism (OA) is characterised by a reduction of pigments in the eye and usually does not affect the colour of the skin and hair. Oculocutaneous albinism comprises four subtypes: OCA1, OCA2, OCA3 and OCA4, with each subtype presenting with a characteristic phenotype and visual acuity (VA).[3]. The classification of albinism is related to the affected genes, the most commonly affected ones being the tyrosinase gene on chromosome 11q14-21, which results in OCA1, and the P gene on chromosome 15q11.2, which results in OCA2. Oculocutaneous albinism results in defects of the visual pathway and ocular structures
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