Fundus Stretch Index: A Centile-Based Retinal Measure of Myopia

Area of Science:

• Ophthalmology
• Medical Imaging
• Biostatistics

Background:

• Myopia is a significant risk factor for several sight-threatening eye conditions.
• Accurate risk stratification for conditions like rhegmatogenous retinal detachment (RD) and primary open-angle glaucoma (POAG) is crucial for early intervention.
• Existing risk models may not fully capture individual risk due to geometric variations in the fundus.

Purpose of the Study:

• To introduce and assess the Fundus Stretch Index (FunSI) as a novel, centile-based metric for quantifying retinal geometric deviation relative to spherical equivalent refraction (SER).
• To evaluate FunSI's potential in stratifying risk for rhegmatogenous RD and POAG.
• To determine if FunSI improves risk prediction models for these conditions.

Main Methods:

• A population-based cohort study involving 25,222 adults with fundus photographs and linked health records.
• Quantile regression to establish centiles for 10 fundus imaging features based on SER.
• Calculation of FunSI as a normalized sum of SER-specific centile positions across features.
• Cox regression to associate baseline FunSI with incident RD and POAG, adjusting for covariates.

Main Results:

• Higher baseline FunSI was significantly associated with an increased risk of developing rhegmatogenous RD (aHR 1.26) and POAG (aHR 1.11).
• The addition of FunSI demonstrated a notable improvement in the concordance index for the RD risk prediction model compared to the POAG model.
• Event rates were 4.9/10,000 person-years for RD and 15.0/10,000 person-years for POAG in the analyzed cohorts.

Conclusions:

• Fundus Stretch Index (FunSI) offers an interpretable method for characterizing myopia at the retinal geometric level.
• FunSI can differentiate long-term risk for sight-threatening diseases between individuals with similar baseline risk factors like SER.
• This metric holds promise for enhancing risk stratification in ophthalmology.