Macular thickness and visual acuity are characterized by a quadratic nonlinear relation in previously treated neovascular AMD eyes

Purpose: To assess the associations between visual acuity (VA) and retinal thickness in age-related macular degeneration (AMD) eyes treated with anti-vascular endothelial growth factor (VEGF) therapy. Methods: Sixty-eight patients with neovascular AMD (68 eyes) undergoing anti-VEGF therapy with two years of follow-up imaging data after the initiation of treatment were retrospectively included. Linear and nonlinear regression analyses with curve fitting estimation were performed to explore the relationship between visual acuity and OCT-based parameters at the 3-month and 24-month follow-up visits. Regression analyses were also performed between visual acuity and the retinal thickness deviation which was calculated as the absolute value of the difference between measured and normative retinal thickness values. Results: The VA was not associated with either foveal (R-2 = 0.011 and p = .401 at 3 months; R-2 = 0.032 and p = .142 at 24 months) or parafoveal (R-2 = 0.045 and p = .081 at 3 months; R-2 = 0.050 and p = .055 at 24 months) retinal thicknesses. Compared with the linear models, a quadratic function yielded a relative increase in the R-2 coefficients. Conversely, the VA was linearly associated with foveal retinal thickness deviation (R-2 = 0.041 and p = .037 at 24 months) and parafoveal retinal thickness deviation (R-2 = 0.062 and p = .040 at 3 months; R-2 = 0.088 and p = .014 at 24 months) values. Conclusions: Although there was no linear relationship between retinal thickness and VA, a weak but statistically significant linear relationship could be observed when a retinal thickness deviation was considered. This suggests that deviation-based parameters may be beneficial for structure-function correlations in the context of anti-VEGF therapy for neovascular AMD.