Geographic atrophy phenotypes in subjects of different ethnicity: Asia-Pacific Ocular Imaging Society Workgroup Report 3.

PURPOSE: To characterize geographic atrophy (GA) and to evaluate differences between Asians and non-Asians.

DESIGN: Retrospective cohort study PARTICIPANTS: Subjects aged ≥50 years with GA secondary to AMD in the absence of neovascularisation in the study eye and follow-up of ≥ 2 years.

METHODS: Multicenter, retrospective case series. GA lesion characterized at baseline and last follow-up based on multimodal imaging (fundus autofluorescence [FAF], near infrared [NIR], SD-OCT). Patients were grouped as either Asian or non-Asian descent.

MAIN OUTCOME MEASURES: Comparison of 1) phenotypes of GA lesions (size, foveal involvement, number of foci, drusen background, choroid background) and 2) growth rate of GA.

RESULTS: A total of 144 patients (169 eyes) with distribution of 50.9% Asians and 49.1% non-Asians. The age and gender were similar between Asians and non-Asians (Asians: mean age 77.2±10.1; 47.9% female; non-Asians: mean age 79.7±8.4; 58.7% female). Asians had thicker choroids (167±74μm vs 134±56μm, p<0.01) and lower prevalence of any drusen (40.7% vs 66.3%, p<0.01). At baseline, the GA area was smaller in Asians versus non-Asians (NIR 3.7±4.6mm2 versus 6.3±6.8mm2 , p=0.01; FAF 2.4±3.4mm2 versus 8.4±9.6mm2 , p<0.01). Asians had fewer GA foci (1.7±1.3versus 2.7±2.2, p<0.01) compared to non-Asians. The proportion with diffuse/banded FAF junctional zone pattern was similar between Asians and non-Asians (44.2% vs 60.2%, p=0.20). Asians had slower GA lesion growth rate compared to non-Asians (NIR 0.7 vs1.9 mm2 /year, p<0.01; FAF 0.3 versus 2.0 mm2 /year, p<0.01; NIR 0.4 vs 0.9mm/year, p<0.001 square root transformed; FAF 0.3 vs 1.0mm/year, p<0.001 square root transformed). Factors associated with GA lesion growth rate are (from highest effect size): ethnicity, junctional zone FAF pattern, baseline GA area, and number of GA foci. Higher GA lesion growth rate was observed in both Asian and non-Asian subgroups with drusen or lesion size and FAF patterns meeting inclusion criteria of recent therapeutic trials, but growth rate remained significantly slower in Asians. Eyes with baseline lesion ≥5mm2 showed the highest growth rate and difference between ethnicities was no longer significant. (2.6 vs 3.3 mm2 /year, p=0.09) CONCLUSIONS: There are differences in GA lesion phenotype, associated features and growth rate between Asians and non-Asians.