Pupil light reflexes mediated by outer retinal versus inner retinal photoreceptors in normal subjects and patients with neuroretinal visual loss

Abstract

Abstract Purpose This study was designed to translate recently published physiological behavior of the melanopsin‐expressing retinal ganglion cells to the clinical setting. Methods 43 normal eyes were tested by recording the pupil light reflex to a Ganzfeld red (620nm+/‐20nm) and blue (480nm+/‐20nm) light stimulus at 3 light intensities (1, 10, and 100 cd/m2) under mesopic conditions. The pupil responses of the normal subjects were compared to patients with outer retinal disease and patients with optic nerve damage. Results In normal eyes at lower intensities, blue light evoked much greater pupil responses compared to red light when matched for photopic luminance. A disparity between the transient and sustained pupil contractions was greatest at the lowest light intensity and decreased with increasing light intensity. Patients with primarily rod dysfunction showed reduced pupil responses to low intensity blue light stimulation.. A patient with genetically confirmed achromatopsia showed selective reduction of the pupil response to high intensity red light stimulation. Patients with optic neuropathy tended to have reduced pupil responses to all light conditions. Conclusion Pupil responses that differ as a function of light intensity and wavelength support the hypothesis that selected stimulus conditions can produce pupil responses that may reflect phototransduction mediated by either rods, cones, or intrinsic activation of melanopsin‐expressing retinal ganglion cells. The pupil light reflex may be used to differentiate diseases affecting either the outer or inner retina.