- Patients who receive an implanted visual prosthesis must undergo vision rehabilitation afterward, but the ideal strategy remains unclear
- In this study, eight university students with normal visual acuity participated in 22 sessions in which they used a simulation of a thalamic visual prosthesis to perform a reading task and/or watch a videotaped episode of the "I Love Lucy" television show
- The reading tasks were associated with significant improvement in visual acuity; on average, the starting value was 1.28 logMAR, and the end value was 1.13 logMAR, for an improvement of -0.15 logMAR (P=0.001)
- Passive viewing of videos was not nearly as effective for improving visual acuity as reading for the same amount of time: the visual perceptual learning rate was 0.009 logMAR/session for the reading task vs. -0.005 logMAR/session for the video task
- For individuals living with a visual prosthesis, passive viewing tasks are likely to occupy a more significant fraction of time than the active tasks tested in clinics, but a passive task doesn't seem to have nearly the same rehabilitative impact
Contemporary visual prostheses only crudely approximate normal vision, so post-implantation rehabilitation is necessary. To determine which training strategies are best, researchers ask normally sighted volunteers to use virtual reality setups that simulate the vision of a nearly blind individual with a prosthesis.
Subscribe to the latest updates from Neuroscience Advances in Motion
This research usually relies on a task that requires concerted effort, such as visual recognition, reading, or visuomotor interaction. However, passive tasks such as watching television will likely occupy a larger fraction of time for individuals living with a visual prosthesis. Incorporating passive viewing tasks into their post-implantation treatment plan may be worthwhile.
To test this hypothesis, John S. Pezaris, PhD, assistant professor in neurosurgery in the Department of Neurosurgery at Massachusetts General Hospital and assistant investigator in the Mass General Research Institute, and colleagues investigated the visual perceptual learning of normally sighted individuals who watched video through simulated artificial vision. In Scientific Reports, they demonstrate that this passive task did not result in an overall sharpening of visual acuity.
The subjects in the experiment were eight university students who were verified to have normal or corrected-to-normal visual acuity. Over 22 sessions, they used a simulation of a thalamic visual prosthesis with 1,000 phosphenes to perform a reading task and/or watch an episode of the "I Love Lucy" television show.
The reading task involved multiple brief trials of phosphene viewing (approximately 30 seconds per trial) interspersed with natural viewing. Participants received feedback for correct answers. Video viewing was much more extended, typically 24 minutes, with no interruptions. Across sessions, participants spent about one minute engaged in reading for about every seven minutes of video viewing.
Reading Test Results
As a population, subjects improved in reading accuracy (percentage of words read correctly) from the first session to the last. However, there was no overall improvement in proficiency with phosphene vision, as no equivalent increase was found in reading speed (number of words correctly read per minute).
The reading tasks were associated with significant improvement in visual acuity. On average, the starting value was 1.28 logMAR and the end value was 1.13 logMAR, for an improvement of −0.15 logMAR (P=0.001).
Contributions of Reading and Video Sessions to Acuity
Passive viewing of videos was not nearly as effective for improving visual acuity as reading for the same amount of time:
- Initially calculated visual perceptual learning rate: −0.015 logMAR/session for the reading task vs. −0.003 logMAR/session for the video task
- Learning rate calculated by linear regression of acuity versus cumulative time spent at each acuity measurement, multiplied by mean session length: 0.009 vs. −0.005 logMAR/session
Thus, a single reading session drove about twice the acuity improvement of a single video session despite being about half as long.
The idea that a patient could improve the utility of their visual prosthesis through an enjoyable pastime like watching television is highly attractive. However, passive viewing doesn't seem to have nearly the impact as an active, at times challenging task that provides clear-cut automatic feedback.
There do appear to be benefits from passively viewing videos, but the gains are much slower per unit of time. Furthermore, data not presented in this summary suggest the benefits don't transfer universally to other visual skills. During post-implant rehabilitation, having patients engage in an active process appears to be preferable.
Learn more about the Department of Neurosurgery
Refer a patient to the Department of Neurosurgery