Long-term atrophy expansion rates in a prospective, longitudinal study of ABCA4 retinopathy using ultra-widefield fundus autofluorescence

Authors

• AS Pathapadu
• MP Boyle
• LA Huryn
• CA Cukras
• WM Zein
• BP Brooks

Abstract

To quantify expansion rate (ER) of retinal pigment epithelium (RPE) atrophy in ABCA4-related retinopathy using ultra-widefield fundus autofluorescence (UWFAF). Further, we sought to determine whether atrophy continues to expand linearly over an extended time scale.
We analyzed 52 eyes from 26 patients with molecularly confirmed ABCA4 retinopathy enrolled in a prospective natural history study with an average 8.3 years of longitudinal follow-up. Atrophy was outlined manually from UWFAF images at each time point. Progression of atrophy was estimated from a longitudinal model using mixed-effects modeling.
A median [IQR] of 20 UWFAF images [15, 25] were analyzed per eye across a median of 9.1 visits [8, 10]. Median [IQR] expansion rates of atrophy expansion were 0.95 mm2/year [0.607, 2.604] for linear growth and 0.20 mm/year [0.12, 0.28] for sqrt growth. Median [IQR] atrophy at baseline was 7.8 mm2 [3.4, 14.2] corresponding to median sqrt atrophy of 2.79 mm [1.9, 3.8]. ER was not correlated with age or size of atrophy at baseline. The average sqrt Area of DDAF at baseline was (mixed-model estimate [95%) CI]) 3.35 mm [2.50, 4.19]. Annual progression was 0.25 mm/y [0.19,0.3].
UWFAF imaging may be used to measure areas of RPE atrophy extending beyond the central retina. The data from this small cohort suggest that atrophy continues to expand linearly in patients with large areas of atrophy at baseline and/or for patients with high atrophy ERs. Measurement of RPE atrophy from UWFAF imaging may serve as a suitable outcome measure in clinical trials of advanced ABCA4 retinopathy.

Scientific Focus Area: Clinical Research

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