Reductions in primary visual cortex volume in patients receiving long-term treatment for neovascular age-related macular degeneration.

Abstract

Purpose : Anti-angiogenic treatment for neovascular age-related macular degeneration (nvAMD) aims to preserve vision. However, despite initial mean gains recovering around 50% of lost vision, visual acuity (VA) often slowly declines over several years. Neuroimaging studies have shown structural reductions of visual cortex volume and grey matter in long-term vision deprivation, if left untreated. This study assessed whether structural changes also occur in primary visual cortex (V1) despite long-term anti-angiogenic treatment for nvAMD.

Methods : Measurements of visual cortical structure, VA (ETDRS score) and 1mm³ subfield central retinal thickness (CRT) measured with spectral domain optical coherence tomography, were performed in 7 nvAMD patients undergoing standard care anti-vascular endothelial growth factor treatment. Assessments took place before treatment commenced, after the treatment initiation phase (1-4 months) and after several years (3.6-5.9 years). T1-weighted magnetic resonance imaging (MRI) measured cortical changes in 3 regions of interest: the entire occipital cortex, V1 representing the affected macula (occipital pole, OP) and peripheral, unaffected retina (calcarine sulcus, CS).

Results : A significant volumetric decrease was found in the entire occipital cortex after long-term treatment (31767 to 28639mm³, p=0.023), primarily due to reduced cortical thickness of the OP (2.11 to 1.94mm, p=0.027) rather than the CS (1.83 to 1.76mm, p=0.174). A linear regression revealed that changes in the entire brain (excluding the occipital lobes) largely explained variance observed in the CS (65%, p=0.029) but did not fully account for reductions in the OP (31.6%, p=0.189). Clinical assessments revealed increased VA during treatment initiation, decreasing slightly with long-term treatment (57, 68, 63 ETDRS, n.s). CRT initially decreased, with signs of stabilisation following long-term treatment (356.2, 263.7, 252.1µm, n.s).

Conclusions : VA improvements following treatment were maintained above pre-treatment levels over the long term, while CRT showed stabilisation. Nevertheless, long-term anti-angiogenic treatment did not prevent significant atrophy of V1 in representations of the retinal regions affected in nvAMD. This study provides a hypothesis about the potential role of visual cortex in long-term vision loss in patients treated for nvAMD.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.