Berkeley Fahrenthold¹, Bryan Redmond¹, Rachel Hollar¹, Jingyi Yang¹, Matthew Cavanaugh¹, Duje Tadin¹, Marisa Carrasco², Krystel Huxlin¹; ¹University of Rochester, ²New York University

Occipital strokes that damage primary visual cortex (V1) and surrounding early visual cortical areas cause homonymous visual deficits, commonly referred to as cortically-induced blindness. These strokes also trigger trans-synaptic retrograde degeneration across early visual pathways. In chronic stroke patients, degeneration at the level of the optic tracts has been shown to predict training-induced visual recovery (Fahrenthold et al., Brain 2021). Here, we investigated whether a similar relation exists in subacute patients (<6 months post-stroke) at the retinal level. Twenty-three patients (49 ±10 years old, 13 males) were recruited 1.2–5.1 months post-occipital stroke as part of an ongoing clinical trial (NCT04798924). Ganglion cell and inner plexiform layer (GCL-IPL) thicknesses on either side of the fovea [corresponding to the blind and intact hemifields] were measured at baseline using optical coherence tomography (OCT) and used to calculate a laterality index (LI). Participants underwent visual training on a direction discrimination task with feature-based attention in two phases. During the subacute period, they were randomized to train in either the intact or blind hemifields, followed by 6 months of training in the blind hemifield during the chronic period. Pre-training, the GCL-IPL LI was small, ranging from -0.012 to 0.032, and it increased with time since stroke (p=0.0120, R2=0.2649). By the end of the study, blind-field direction discrimination thresholds had significantly improved (paired t-test, p=0.0001), irrespective of baseline GCL-IPL LI (p=0.1805, R2=0.0923). Similarly, training significantly reduced the size of the Humphrey-defined visual field deficit (paired t-test, p=0.0002), also irrespective of baseline GCL-IPL LI (p=0.1410, R2=0.1105). In summary, initiating visual training during the subacute period after occipital stroke provides significant perceptual benefit for all participants. In contrast to chronic patients, this improvement occurs irrespective of the small degree of baseline retrograde degeneration in the retina, which can be reliably detected using OCT.

Acknowledgements: Supported by NIH funding (R01 EY027314 to KRH, as well as T32 EY007125 and P30 EY001319 to the Center for Visual Science) and by an unrestricted grant from the Research to Prevent Blindness (RPB) Foundation to the Flaum Eye Institute