Study identifies genetic causes of inherited eye conditions in Scotland

IRDs, caused by mutations which lead to death of the light sensing photoreceptor cells at the back of the eye, are the leading cause of sight loss in children and adults of working age.

More than 300 genes which carry these mutations have been identified and gene therapy approaches are emerging to treat this devastating disease.

However, as most of these approaches are gene specific, identification of the causative mutation is required in order to identify which patients are eligible for these treatments and trials.

NHS England has implemented a ‘whole genome sequencing’ approach to diagnosing genetic disease, including IRDs, while the Scottish Government has developed its own conventional panel test of a curated set of genes known to be associated with IRDs.

The study, led by researchers at the University of Edinburgh, assessed the occurrence of IRDs in the Scottish population in the five years leading up to this switch. 

Using data from all patients presenting to ophthalmology services across Scotland from January 2018 to January 2023 diagnosed with an IRD, the researchers identified the most common genetic causes of IRDs in Scotland, the percentage of patients who received a ‘positive’ genetic diagnosis to explain their IRD, and the time taken to reach this diagnosis.

Of more than 530 patients included in the analysis, the most common clinical diagnosis was retinitis pigmentosa - RP (42.4%), followed by Stargardt Disease (9%).

The most common initial test was a 176 gene panel, followed by direct testing for ABCA4, with different regions pursuing different testing strategies.

More than two thirds (67.4%) of patients received a molecular diagnosis. The most common causal gene was ABCA4, followed by USH2A and RDS/PRPH2.

This study provides a unique insight into the Scottish ophthalmic genetics service and serves as a benchmark for iterative improvement.

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