Elucidating the genetic landscape of inherited retinal disorders in India

Inherited retinal diseases (IRDs) are highly diverse and rare genetic disorders causing mild to complete vision loss across different age groups, with a notably higher disease burden in India. Although genetic testing has improved diagnostic accuracy, India's distinct genetic landscape, shaped by diverse racial backgrounds, admixtures, endogamy, and consanguinity, presents unique challenges. Additionally, phenotype overlaps, non-canonical presentations, genetic heterogeneity, and insufficient literature evidence contribute to clinically and genetically unsolved cases. Since genetic variant reporting commonly relies on information from non-Indian population databases, it is important to build comprehensive knowledge from published Indian data for its unbiased representation in relevant clinical resources. This review aims to assess the current state of Indian IRD research and its lacunae, as this understanding is essential to gauge the readiness of research institutions and tertiary centres for maximizing accessibility to genetic testing and potential treatment options.

We screened 764 PubMed-sourced Indian IRD articles until October 2023 and analysed 21,158 IRD cases from 287 publications reporting clinical and/or genetic data, and further found that 80 publications (n = 628 cases) reported genetic variants (v = 686 variants). Relevant literature was analysed to assess demographic distribution, genetic trends and the research landscape in India.

Our analyses draw a comprehensive sketch of publication-derived demographics and genetic insights into major IRDs reported in India. They emphasize the urgent need for comprehensive and timely clinical and genetic reporting, since Indian IRD research remains fragmented. This calls for integrated nationwide efforts in systematic reporting through an extensive national IRD case registry for improving diagnostic accuracy, enhancing patient recruitment for clinical trials, and expanding access to emerging therapeutics.