Author Response: Test-Retest Reliability of Hemifield, Central-Field, and Full-Field Chromatic Pupillometry for Assessing the Function of Melanopsin-Containing Retinal Ganglion Cells.

Abstract

PURPOSE We evaluated the test-retest reliability of current methods of inducing the melanopsin-driven postillumination pupil response (PIPR) under hemifield, central-field, and full-field stimulation conditions. METHODS Pupil response was recorded with an eye tracker in 10 visually normal participants. Light stimuli were presented using a Ganzfeld screen with a custom-built device that allows specific regions of the retina to be stimulated. Blue light stimulation at 400 cd/m(2) intensity was presented for 400 ms to the lower and upper halves of the central 30° fields (hemifields), central 30° field (central-field), and full-field to induce PIPR. Red light full-field stimulation also was presented with the same intensity and duration as a control condition. Test-retest reliability of the PIPR measures was assessed by calculating the intraclass correlation coefficient (ICC) of six repetitions for lower and upper hemifield stimulation, and three repetitions for central-field and full-field stimulation. RESULTS Hemifield, central-field, and full-field blue light stimulation induced increasingly greater PIPR in ascending order, while full-field red light stimulation induced no PIPR. Mean lower and upper hemifield PIPR was highly symmetric. Mean ICC of blue light PIPR was 0.87 for lower hemifield, 0.88 for upper hemifield, 0.95 for central-field, and 0.94 for full-field stimulation. CONCLUSIONS We validated a new and repeatable method to measure PIPR induced by hemifield, central-field, and full-field light stimulation. Good PIPR measurement reliability was obtained under all conditions. This practical and reliable protocol will facilitate the clinical application of PIPR testing in different disease populations.