Secondary Ophthalmic Features Represent Diagnostic Clues and Potential Points of Intervention for Inherited Retinal Diseases (Target 5000 Report 3)

Background/Objective: Inherited retinal degenerations (IRDs) are the leading cause of blind registration in children and adults, yet 30–40% of cases remain genetically unresolved. Deep ophthalmic phenotyping may help to address this shortfall by identifying characteristic phenotypes. We describe the ophthalmic features of patients with stationary or progressive inherited retinal diseases other than outer retinal degeneration (i.e., secondary ophthalmic features, SOFs). Methods: This is a retrospective review of all patients attending an ophthalmic genetics clinic with a genetically confirmed IRD focusing on SOFs including refractive error, cataract, retinal detachment (RRD), cystoid macular lesions (CML) and epiretinal membrane (ERM). These features were assessed in the context of phenotype and genotype. Results: In a cohort of 429 genotyped patients, ≥1 SOFs were seen in 70.2% of patients, with 36.6% being affected by multiple SOFs. Refractive error (63.3%) and cataract (43.4%) were the most common secondary features, with a subset affected by CML (14.7%), ERM (10%) and RRD (4.7%). Conclusions: SOFs are common in patients with IRDs and most are amenable to therapeutic intervention even when no primary treatment (e.g., gene therapy) is available. We highlight patterns associated with genotypes and disease groups which may aid harmonisation of clinical and genetic diagnoses.