The Impact of Vision Restoration on Visual Cortical Structure

Abstract

The Argus II retinal prosthesis restores low-resolution visual perception to late blind patients. It has been shown that structural changes occur in the brain due to late-onset blindness, including cortical thinning in visual regions of the brain. Following vision restoration, it is not yet known whether these visual regions are reinvigorated and regain a normal cortical thickness or retain the diminished thickness from blindness. We evaluated the cortical thicknesses and subcortical volumes of Argus II patients (N=6), blind patients (N=10), and sighted participants (N=4) with a Siemens 3T MRI scanner (64-channel head coil) at USC. Age-matched sighted controls (N=6) from the Lifespan Human Connectome Project Aging (HCP-A) database were also included (Siemens 3T MRI scanner with a 32-channel head coil). We compared the cortical thicknesses of the occipital lobe regions delineated by the Desikan-Killiany atlas between the participant groups. The visual regions in the two sighted participant groups (USC and HCP-A) did not show a significant difference in cortical thickness, and therefore are included in one sighted group. The blind patients were shown to have a reduced cortical thickness in the left Cuneus Cortex, the left Lingual Gyrus, and the left Lateral Occipital Cortex, and a reduced volume of the right Lateral Geniculate Nucleus (LGN) relative to the sighted controls. The Argus II patients had a reduced cortical thickness in the left Lingual Gyrus, and a reduced volume in the right LGN relative to the sighted controls. However, the Argus II patients had a thicker left Lateral Occipital Cortex relative to the blind patients. Overall, the Argus II patients did not show a reversal of the blindness-driven thinning of grey matter in early visual regions. However, Argus II patients’ cortical thickness was rejuvenated in one higher visual region.