Purchase this article with an account.
Vincent Jonas BISMUTH, Matthias Keserue, Lars Wagenfeld, Tim Schade, Yannick Le Mer, Omar Darwiche-Domingues, Ralf Hornig; Retinotopy of percepts elicited by an IRIS epi-retinal implant. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4190.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The retinotopy of phosphenes elicited by visual prostheses conditions the performance of such systems and should drive stimulation strategies. We explore here the relationship between electrode position and perceived phosphene location in the visual field. We report data from the ongoing IRIS V1 clinical study (NCT01864486 – Sponsor: Pixium Vision). This is the first publication of this kind with an IRIS epi-retinal implant.
An IRIS V1 epi retinal implant system with 49 electrodes was implanted in a human clinical trial. Individual electrodes were stimulated in random order at various stimulation levels. Every time the patient had a percept, he reported its position though a touchscreen. The collected data for stimulation levels between 0.8 and 2.0 times the perception thresholds were analyzed. We computed the Pearson correlation between electrode locations on the implant and phosphene positions. Moreover, we fitted the phosphene positions with affine and polynomial models, computed coefficients of determination for each model and provided graphical representations of the data. We report data collected in two sessions, 6 weeks apart, in 2016.
46 out of 49 electrodes elicited perception. 140 location data points were recorded. The Pearson correlation between the x (resp. y) coordinate of the implant and the x (resp. y) coordinate of the phosphene locations is 0.85, p <0.001 (resp. 0.89 p < 0.001). The affine model fits to the data with an R^2 of 0.77 and the third order polynomial model with an R^2 of 0.81. The left part of Figure 1 represents the electrodes on the implant with color coding. Its right part depicts the average position of phosphenes for each electrode. Figures 2 illustrates affine fit on the left and polynomial fit on the right. For all phosphene position graphs the scale is cm on a screen located at 30cm from the patient's head.
The strong and statistically significant correlations between electrode positions and phosphene locations together with the strong R^2 obtained with affine and polynomial models demonstrate retinotopic perception of phosphenes. The fact that the data was collected in two sessions moreover demonstrates stability of this retinotopic organization over time.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
This PDF is available to Subscribers Only