Visual Acuity and Genetic Classification of Subjects with either Type I or Type II Oculocutaneous Albinism

Abstract

 

Purpose

 

Albinism is a genetic disease in which different mutations can cause the absence or reduction of melanin, leading to ophthalmologic changes that may include severe visual loss. The most common mutations are present in either the Tyrosinase (OCA1) gene or the P gene (OCA2). These two types of albinism can be dermatologically differentiated, although this classification is imprecise. To screen the TYR and the P gene of albino subjects in a Brazilian cohort and compare the genetic results with previous dermatological diagnoses. In addition, to correlate visual acuity to an individual’s respective type of albinism.

 

Methods

 

We evaluated 11 subjects, 5 of which were pre-diagnosed as OCA1, 4 as OCA2, and 2 were ambiguous between the two types of albinism. All individuals were genotyped for all the exons of the TYR gene and for selected exons of the P gene. Visual acuity was evaluated using an Early Treatment Diabetic Retinopathy Study chart.

 

Results

 

Of the 11 albino subjects, 3 had mutations in the TYR gene (OCA1) and 8 were confirmed as OCA2, two of which had been initially classified as OCA1 (Table 1).

 

Conclusions

 

These results show the need for genetic analysis in confirming the type of albinism. There were differences between visual acuities of individuals who had the same type of albinism. This is most often attributed to the differences in iris/retina pigmentation and macular development. The correlation drawn in this study between general visual acuities and OCA1/OCA2 individuals, along with the ongoing investigation of Brazilian albinos, can serve as a basis from which a more precise, efficient diagnosis and treatment standard can be formed for the genetic disorder of albinism.

 

 

Keywords: 463 clinical (human) or epidemiologic studies: prevalence/incidence • 539 genetics • 754 visual acuity