Thinning of the Retinal Nerve Fibre Layer in Homonymous Quadrantanopia: Further Evidence for Retrograde Trans-Synaptic Degeneration in the Human Visual System

This investigation is a cross-sectional study of peripapillary retinal nerve fibre layer (RNFL) thickness in a cohort of homonymous quadrantanopia (HQ) patients with evidence of post-geniculate pathology. Forty-four cases were recruited and divided into three groups; 14 acquired HQ cases; 7 congenital HQ cases; and lastly 23 control individuals. Compared with the controls, RNFL thinning was most obvious at the superior sector in inferior quadrantanopia and at the inferior sector in superior quadrantanopia as would be expected from the known fibre trajectories. The findings are likely to reflect retrograde trans-synaptic degeneration in cases of post-geniculate damage lesser in extent than those previously studied. A further analysis was carried out comparing RNFL thickness (overall, mean of the two eyes) with the Humphrey mean deviation score (mean of the two eyes). For this analysis, data of an additional 28 patients with dense homonymous hemianopia and three cases with sub-quadrantic homonymous scotoma were also included. A statistically significant straight line relationship was found (r = 0.5, p < 0.001), indicating a strong correlation between the RNFL thinning and the visual deficit.