# Visual–tactile shape perception in Argus II Participants: The impact of prolonged device use and blindness on performance

## TL;DR

Long-term users of the Argus II retinal prosthesis show initial improvements in shape perception, but prolonged blindness may hinder performance.

## Contribution

This study reveals individual differences in performance over prolonged Argus II use and the negative impact of prolonged blindness on visual restoration.

## Key findings

- Multisensory performance improves initially with Argus II use up to 42 months.
- Prolonged blindness correlates negatively with task performance in Argus II users.
- Argus II users show significant differences in sensitivity and bias compared to controls in shape tasks.

## Abstract

In Stiles et al. (2022), we showed that experienced Argus II retinal prosthesis users could accurately match visual and tactile shape stimuli (n = 6; ≤42 months of use). In this follow-up paper, we studied longer using participants (n = 5; ≤121 months of use) to evaluate visual and multisensory performance over prolonged visual restoration. With the combined cohort of participants from both studies (N = 11), we found that there was a significant positive correlation in multisensory performance up to the median duration of use (42 months) and a positive slope fit but not a significant correlation for the median duration of use and beyond. Therefore, there seems to be evidence for initial performance improvement with Argus II use. Nevertheless, there is also evidence for substantial individual differences with more extended device use, supported by a participant self-evaluation/questionnaire. Variations in the frequency of device usage, device functionality, or neurostructural plasticity could contribute to these individual differences. We also found a negative correlation in Argus II participants (N = 11) between task performance and the duration of blindness, potentially indicating the deleterious effects of atrophy and neurostructural changes during blindness on visual restoration functionality. Finally, a d′ analysis showed that the Argus II participants in all tasks (including tactile–tactile matching) had significant differences in sensitivity and bias relative to controls, highlighting variation in the shape task strategy. Overall, these data highlight individual differences in performance over prolonged device use and the negative impact of prolonged blindness on visual restoration.