Multimodal imaging determinants of contrast sensitivity loss in geographic atrophy.

AIMS: To investigate associations between imaging biomarkers and quantitative contrast sensitivity (CS) function (qCSF) metrics in geographic atrophy (GA).

METHODS

Cross-sectional study including 97 eyes from 70 patients (>55 years) with GA within 1500 µm of the fovea and visual acuity (VA)>20/320. Participants underwent VA and qCSF testing (area under the log CS function (AULCSF), contrast acuity (CA), and CS at 1-18 cycles per degree (cpd)) and multimodal imaging with blue autofluorescence (BAF), optical coherence tomography (OCT), and, in 55 eyes, swept-source OCT angiography (SS-OCTA). Imaging biomarkers included GA size, prior growth rate, configuration, BAF pattern, circularity, percentage of foveal involvement (%FI), foveal distance and macular inner choroid flow deficit percentage (mICFD%). Generalised linear mixed-effects and random forest (GRF) models evaluated structure-function relationships.

RESULTS

Participants (age 78.8±5.6 years; 70% female) had a median GA size of 4.0 mm², with 64% showing subfoveal involvement. Larger GA size and higher %FI were significantly associated with worse VA, AULCSF, CA and CS at 1-12 cpd (all p<0.01). Unifocal lesions correlated with lower VA and CS at 6 cpd, while diffuse/banded BAF patterns and greater mICFD% were linked to reduced CS at 1-1.5 cpd. GRF analysis identified GA size and %FI as primary predictors of CS loss, with best performance for AULCSF and CS at 3 cpd (R²=0.319, 0.314).

CONCLUSIONS

GA size and %FI are key determinants of CS loss in GA. qCSF outperformed VA in predictive accuracy, supporting its use as a sensitive functional endpoint in GA trials.