Widespread Thinning of Human Primary Visual Cortex Following Focal Loss of Photoreceptors

Abstract

Purpose : Visual field representation is preserved throughout the visual system. Inherited retinal dystrophies resulting in photoreceptor death cause characteristic patterns of visual field loss. Previous work has shown secondary remodelling in the inner retinal layers which raises the question of whether these changes are transmitted along the visual system to V1.

Methods : A cohort of patients with choroideremia (peripheral vision loss) and Stargardt disease (central vision loss), and age- and sex-matched control participants underwent visual field testing and T1 structural MRI scanning. Retinal thickness and visual field sensitivity were analysed in terms of degrees of visual space. Neuroimaging data was analysed using the free open cloud platform brainlife.io. An automated processing pipeline combining FreeSurfer and the approach developed by Benson and colleagues, was used to analyse V1-cortical thickness according to degrees of visual space represented. Repeated measures ANOVA with Huynh-Feldt adjustment were conducted for V1 thickness.

Results : In both patients groups, V1 thickness changed across eccentricities compared to controls (P = 0.01 in Stargardt patients and P < 0.01 in choroideremia). The key changes occurred across all eccentricities in choroideremia patients and between two and six degrees in the Stargardt patients. V1 thickness was not significantly correlated to microperimetry threshold (ρ=0.08, P=0.56) or octopus periphery score (ρ=0.10, P=0.45).

Conclusions : There is evidence of V1 thinning following retinal damage. A generalised effect of photoreceptor loss in the visual cortex due to retinal disease is not currently taken into account when planning retinal treatment. These effects along the visual pathway may require additional intervention to limit the impact of eye disease on brain tissue. We must consider the visual system as a whole rather than in terms of eye or brain.

This is a 2021 ARVO Annual Meeting abstract.