Abstract
Trans-synaptic retrograde degeneration in the early visual system follows damage to primary visual cortex (V1). Inner retinal shrinkage measured with optical coherence tomography (OCT) was reported in V1-damaged patients as early as 3 months, increasing out to 2 years post-stroke (Jindahra et al., 2012). We recently documented the presence of residual, conscious discrimination abilities in the blind-field of subacute (<6 months) V1-stroke patients. Here, we asked if maintenance of inner retinal structures underlies this preservation. Using a high-contrast, random dot stimulus, 22 CB participants (mean+/-SD: 3.3+/-1.2 months post stroke) were assessed for visual discrimination ability (% correct >72.5% and measurable direction difference threshold) in their perimetrically-defined blind field (<10 dB of luminance sensitivity on Humphrey Automated Perimetry). Thicknesses of the ganglion cell (GCL) and inner plexiform (IPL) layers of the retina were measured using a Spectralis HRA+OCT and contrasted between affected and unaffected segments of the para-foveal region out to 12˚ eccentricity. From these thicknesses, we computed a laterality index (LI) to indicate relative shrinkage of the affected regions in each patient. Blind-field discrimination abilities were found in seven of the 22 participants. LI:GCL/IPL averaged 0.008+/-0.017 across the entire cohort, -0.006+/-0.016 in preserved CB patients, and 0.014+/-0.014 in non-preserved patients. A significant difference in LI:GCL-IPL (unpaired t-test, p = 0.009) was found between these two groups. LI:GCL/IPL increased with time since stroke (r-squared = 0.3269, p = 0.0054), but seemed uncorrelated with the perimetrically-defined, blind-field size (r-squared = 0.1442, p = 0.081). Thus, early V1-stroke patients with preserved visual abilities exhibit less thinning of inner retinal layers than those without. Given the sensitivity of OCT imaging shown in the present experiment, we are now ideally placed to explore both the prognostic implications of inner retinal preservation for vision restoration, and potentially neuroprotective effects of behavioral interventions in this patient population.