Foveal Avascular Zone Enlargement Correlates with Visual Acuity Decline in Patients with Diabetic Retinopathy.

purposeThe foveal avascular zone (FAZ) area has been explored as a measure of macular ischemia in diabetic retinopathy (DR) but is limited by its wide variability even in healthy individuals. We hypothesized that FAZ enlargement, defined as the difference between the functional FAZ (on OCT angiography [OCTA]) and structural FAZ (on en face OCT), may be a more accurate metric of macular ischemia. In this study, we test the hypothesis that FAZ enlargement is associated with decreased best-corrected visual acuity (BCVA) and low-luminance visual acuity (LLVA) and performs better than the functional FAZ as a marker of vision loss.

designCross-sectional study. SUBJECTS: Patients with diabetes mellitus (DM) and a wide range of DR severity.

methodsFor 264 eyes from 174 patients, we measured BCVA and LLVA using ETDRS letter scores. Averaged en face OCT and OCTA scans identified structural and functional FAZ areas, respectively. Spearman's ρ quantified relationships between FAZ enlargement and visual acuity, which were further assessed with linear mixed-effects models that accounted for potential confounders, which were identified using univariate analysis.

main outcome measuresRelationship between FAZ enlargement (or functional FAZ area) and visual function.

resultsAge, axial length, lens status (phakic or pseudophakic), hypertensive status, ischemic heart disease, cerebrovascular disease, renal disease, dyslipidemia, DR severity, and functional FAZ area correlated with BCVA on univariate analysis. Age, body mass index, hypertension, ischemic heart disease, renal disease, dyslipidemia, smoking status, DR severity, and functional FAZ area correlated with LLVA on univariate analysis. Foveal avascular zone enlargement demonstrated a weak negative correlation with BCVA (ρ = -0.364, P < 0.001) and LLVA (ρ = -0.306, P < 0.001), which remained significant in mixed-effects regression analysis. Functional FAZ area was not a significant predictor of BCVA or LLVA in models where FAZ enlargement was also included as a predictor. Model comparison using analysis of variance indicated that inclusion of FAZ enlargement improved the prediction of BCVA (chi-square = 5.62, P = 0.018) and LLVA (chi-square = 4.99, P = 0.025).

conclusionsFoveal avascular zone enlargement performed better than the functional FAZ providing an improved imaging metric of the influence of foveal ischemia on vision impairment in DR. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.