Original article
Visual Performance Using a Retinal Prosthesis in Three Subjects With Retinitis Pigmentosa

https://doi.org/10.1016/j.ajo.2007.01.027Get rights and content

Purpose

To assess visual task performance in three blind subjects implanted with epiretinal prostheses.

Design

Prospective, investigational device exemption trial.

Methods

Three subjects with light perception or no light perception vision were enrolled at a single center. All subjects had retinitis pigmentosa (RP). Main inclusion criteria: light perception or worse vision in one eye and some visual experience as an adult before blindness. Main exclusion criteria included other ophthalmic problems. A prototype retinal prosthesis was implanted in the eye with worse light sensitivity. The prosthesis had 4 × 4 array of platinum electrodes tacked to the epiretinal surface. The prosthesis was wirelessly controlled by a computer or by a head-worn video camera. Visual function testing was performed in single masked or double masked fashion. Scores from the visual task were compared to chance to determine statistical significance.

Results

The subjects performed significantly better than chance in 83% of the tests. Using the video camera, subjects scored as follows on simple visual tasks: locate and count objects (77% to 100%), differentiate three objects (63% to 73%), determine the orientation of a capital L (50% to 77%), and differentiate four directions of a moving object (40% to 90%). A subset of tests compared camera settings using multipixels vs single pixels. Using multipixel settings, subjects performed better (17%) or equivalent (83%) in accuracy and better (25%) or equivalent (75%) in reaction time.

Conclusions

Three RP implant subjects used epiretinal prostheses to perform simple visual tasks. Multipixel settings proved slightly more effective than single pixel settings.

Section snippets

Methods

This study protocol was granted an Investigational Device Exemption by the US Food and Drug Administration and was approved by the Institutional Review Board at the University of Southern California. This research adhered to the tenets of the Declaration of Helsinki. The trial is registered at the National Institutes of Health (trial identifier NCT00279500).

Experiments Using Computer Input

Subjects scored better than chance in eight of nine computer-controlled experiments (see Figure 2). When asked to identify which of two electrodes had been presented (experiment 1), all of the subjects performed significantly better than chance (S1 = 72%, S2 = 100%, S3 = 67%; P < .01). This suggested that the percepts elicited by individual electrodes remain reasonably consistent over short periods. In experiment 2 (sequential activation of paired electrodes), all three subjects performed

Discussion

The safety and feasibility of microelectronic implants has been supported by several recent studies, and the relative merits of epiretinal and subretinal retinal implants vs other approaches such as optic nerve cuffs and cortical implants has been extensively discussed in the literature.5, 6 Recent clinical trials of retinal implants have included a passive subretinal device, an active subretinal device (Zrenner E, et al. IOVS 2006;47: ARVO E-Abstract 1538), and an active epiretinal device

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