Pupillary Light Responce in Blind Patients With Epiretinal Prostheses

Abstract

Abstract: : Purpose:Artificial visual perception produced by the 16 electrode intraocular retinal prosthesis (IRP) has been reported in the past, yet the presence of a measurable pupillary light reflex (PLR) has not been confirmed in these patients. We set to determine the existence of and characterize the PLR in no light perception (NLP) and bare light perception (LP) human Retinitis Pigmentosa (RP) patients through electrical stimulation of the retina using the 16 electrode epiretinal IRP. Methods:Pupillography was performed in September 2004 on five RP patients who were implanted with IRPs between February 2002 and March 2004. All five patients were determined to be NLP or bare LP and without a clinically apparent PRL prior to implantation of the prosthesis. Evaluation of the consensual PRL was performed in a dark room with an infrared video camera monitoring pupil diameter at 29.97 frames/sec. Individual frames were analyzed using video and image editing software. Various electrical stimuli parameters were selected for each patient to allow for characterization of pupil constriction in terms of intensity, frequency, and duration of electrical stimuli. Multiple measurements were recorded and averaged for each set of stimuli parameters. Results:All five patients demonstrated measurable pupil constriction in response to stimulation with their IRP. Electrical stimuli parameters set to produce optimal visual perception for 2 seconds resulted in an average percent pupil constriction of 23% SD 7.5%. The average time to maximum pupil constriction at these settings was 1557 msec SD 327 msec. Average latency of onset of constriction was 510 msec SD 195 msec after the initiation of the stimulus. Conclusions:This is a novel study of the PRL in five blind human RP patients that received the IRP. Our results suggest that electrical stimulus of the retina from the epiretinal prosthesis is sufficient to activate the afferent limb of the PRL. Pupillography in patients with an IRP provides an objective physiologic measure of prosthesis function.

Keywords: pupillary reflex • retina • pupil