Genetic Research on Ocular Health and Disease in a Population from Nepal

Ocular disease is a major public health concern worldwide, including Asia where large numbers of individuals suffer from blindness and visual impairment. In South Asian countries like Nepal, for example, age-related cataract is a leading cause of blindness and visual impairment. Age-related cataract is influenced by a complex interplay of non-genetic and genetic risk factors. Identifying the genetic risk factors involved can help elucidate the causal biological mechanisms underlying the development and progression of cataract and help identify those individuals at high risk of disease. The primary objective of an ongoing study in the Jirel ethnic group of eastern Nepal (the Jiri Eye Study) is to define the genetic architecture of normal ocular trait variation and characterize genetic factors influencing risk for common ocular diseases such as cataract. The Jirel population has been the focus of genetic epidemiological studies for more than two decades, and a well-documented extended pedigree has been developed for the group making it extremely powerful and informative for genetic studies. All 1292 study participants discussed in the work presented here belong to this single extended pedigree. Members of the Jirel population underwent a comprehensive eye examination that included lens opacity grading in accordance with the Lens Opacities Classification System II (LOCS II). A variance components method was used to estimate heritability of cataract. Of the 1292 participants, 57.0% were female and 43.0% were male. The mean (SD, range) age at exam is 42.0 (16.7, 18–88) years. The prevalence of cataract (any type) in individuals aged 40 years or older is 25.8%, and additive genetic effects (48.3%) play a significant role in determining the risk of developing cataract in this population. The Jirel population is a powerful resource for the study and identification of genetic mechanisms influencing variation observed in ocular health and disease metrics. We anticipate that the Jiri Eye Study will continue to make significant contributions to the genetics of ocular health and disease in Asia.