# Inherited retinal disorders in Scotland: A 5 year assessment

## TL;DR

This study assesses inherited retinal disorders in Scotland over five years, finding that most patients received a molecular diagnosis.

## Contribution

The study provides the first 5-year assessment of inherited retinal disorders in Scotland and evaluates diagnostic approaches and outcomes.

## Key findings

- Retinitis pigmentosa was the most common clinical diagnosis (42.4%).
- 67.4% of patients received a molecular diagnosis.
- ABCA4 was the most common causal gene identified.

## Abstract

Inherited Retinal Disorders (IRDs) are a leading cause of blindness in working age adults. With the emergence of therapeutic approaches and pre-implantation genetic testing, obtaining a molecular diagnosis is increasingly important. As such we aimed to determine the caseload of IRD patients presenting to Scottish ophthalmology services over a 5-year period, and evaluated the diagnostic approaches used and results of genetic testing in order to determine any established inherited cause.

Data from all patients presenting to ophthalmology services across Scotland from January 2018 to January 2023 diagnosed with an IRD were collected. History and examination findings were recorded, as were the methods of genetic testing used, the identified genetic variants and the time taken for molecular reporting.

532 patients were included in the analysis. The most common clinical diagnosis was retinitis pigmentosa (RP) (42.4%), followed by Stargardt Disease (9.0%), with Usher syndrome the most common syndromic RP. The most common initial test was a 176 gene panel, followed by direct testing for ABCA4, with different regions pursuing different testing strategies. 67.4% of patients received a molecular diagnosis. The most common causal gene was ABCA4, followed by USH2A and RDS/PRPH2.

This study provides the first assessment of IRDs in Scotland over a 5 year period. We demonstrate that the most common clinical diagnoses are RP and Stargardt disease, and that the majority received a molecular diagnosis. This work provides a unique insight into the Scottish ophthalmic genetics service and serves as a benchmark for iterative improvement.