Evaluation of pupillary redilation after colored light stimulation in patients with outer retinal photoreceptor disease

Abstract

Abstract Purpose Stimulation with selective wavelength light has been used to preferentially activate the different types of retinal photoreceptors in humans and thus evoke a differential pupil response to red and blue light. Patients who have outer retinal photoreceptor disease with preserved inner retinal function show a loss of pupil contraction to bright red light and dim blue light. It is hypothesized that the greater inner retinal contribution to the pupil signal in these patients is also reflected in the pupillary re‐dilation after colored light stimulation. Methods Fourteen patients with retinitis pigmentosa were tested using a previously described stimulus paradigm using a long wavelength (red) or short wavelength (blue) light given as a continuous Ganzfeld stimulus with 3 stepwise increases in intensity over a 2 log‐unit range. The pupillary movement before, during and after the light stimulus was recorded in real‐time with an infrared illuminated video camera. Pupillary re‐dilation was measured using 2 parameters: acceleration during the initial 10 seconds after light termination and time‐to‐recover to 90% of baseline pupil size. Results The pattern of pupillary re‐dilation was varied. Some patients showed a prompt return to baseline size following either light stimulation with red or blue light, similar to that seen with normal subjects. Others showed a delayed pupillary re‐dilation either after red and blue light stimulation or after blue light stimulation only. Conclusion Analysis of the differential pupil response and the pattern of subsequent pupillary re‐dilation may be a novel method for identifying patients who have outer retinal photoreceptor dysfunction.