Temporal Properties of Visual Perception on Electrical Stimulation of the Retina

Abstract

Percepts differed considerably across subjects, probably because of the considerable variations in the progression and remodeling processes associated with the disease. Appropriate coding of a patterned image under such conditions appears challenging. Further research of the underlying mechanisms of visual perception upon electrical stimulation of the retina is required to optimize stimulation paradigms and to better establish patient selection criteria.

Electrically Elicited Visual Evoked Potentials in Argus II Retinal Implant Wearers

“…Perceptual ''fading'' was described recently by Pérez Fornos et al in Argus II subjects. 42 They report a decline in phosphene brightness within seconds after the start of stimulation, contrasting the fading we described in our subject, which progressed over a course of 12 minutes. The difference might be explained by different stimulation rates; they used 5 to 60 Hz, while we used 1 / 3 Hz.…”

Response variability to high rates of electric stimulation in retinal ganglion cells

“…Interestingly, our findings also suggest that if Horsager et al had used a longer pulse train, most ganglion cells might have stopped generating one spike for each pulse part way through the train. This likely would have altered the properties of the percept midway through the stimulus and might also have contributed to the relatively fast fading of percept brightness that occurred in other clinical trials (Perez Fornos et al 2010).…”

Electronic restoration of vision in those with photoreceptor degenerations

“…All subjects were able to perceive light and some were able to locate objects, identify direction of motion and distinguish orientations of black and white gratings. 20,30,33 Moreover, four of five patients with some residual vision showed improved accuracy in localising objects with the device turned on, suggesting that patients are capable of 'combining' prosthetic vision with any residual vision. 20 In contrast to the Argus II, the EPIRET3 device, from The University of Marburg, is designed to be completely implanted within the eye without the need for any cabling to pass through the sclera.…”

“…Following stimulation, nine out of ten patients implanted with the Argus II device reported fading of a white/yellow visual percept within ten seconds and some as quickly as two seconds. 33 Changing stimulus parameters led to individual variations in visual perception but did not eliminate the rapid fading of the percept. 33 This means that patients would need to interpret image 'flashes', before they fade.…”

“…33 Changing stimulus parameters led to individual variations in visual perception but did not eliminate the rapid fading of the percept. 33 This means that patients would need to interpret image 'flashes', before they fade. Similar observations were made in patients implanted with a subretinal array that directly stimulated overlying neurons.…”