Full-field Chromatic Pupillometry for the Assessment of the Postillumination Pupil Response Driven by Melanopsin-Containing Retinal Ganglion Cells

Jun 14, 2014Investigative ophthalmology & visual science

Measuring the pupil’s lasting response to light from specialized eye cells using full-field color testing

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Abstract

Full-field blue light at 400 cd/m² intensity induced significantly more sustained pupil response than central-field stimulation.

Pupil response increased consistently with higher stimulus intensity.
A full-field blue light stimulus at 400 cd/m² produced larger pupil responses compared to a central-field stimulus at the same intensity.
Pupil response increased with longer stimulus durations up to 200 ms, but did not increase further from 400 to 1000 ms.
The findings suggest that pupil response is influenced by both the intensity and duration of the stimulus, as well as the area of the retina stimulated.

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PURPOSE: The postillumination pupil response (PIPR) is produced by intrinsically photosensitive retinal ganglion cells (ipRGCs). We aimed to refine the testing conditions for PIPR by investigating whether a greater PIPR can be induced using full-field light stimuli of shorter duration and lower intensity than that produced by existing protocols that use central-field stimuli.

METHODS: Pupil response was recorded with an eye tracker in 10 visually-normal subjects. Red and blue light stimuli were presented using a Ganzfeld system. In Experiment 1 (intensity trials), PIPR was induced using 1-second full-field stimuli of increasing intensities from 0.1 to 400 cd/m(2) (11 steps). For comparison, PIPR also was induced using a 60° × 90° central-field blue stimulus of 400 cd/m(2). In Experiment 2 (duration trials), PIPR was induced using 100 and 400 cd/m(2) full-field stimulus of increasing duration from 4 to 1000 ms (10 steps).

RESULTS: Results indicated that PIPR increased monotonically with increasing stimulus intensity. Full-field stimulation using blue light at 400 cd/m(2) intensity induced significantly more sustained PIPR than central-field stimulation (P = 0.001). In addition, PIPR increased as the stimulus duration increased from 4 to 200 ms; however, no further increase in PIPR was observed when the duration increased from 400 to 1000 ms.

CONCLUSIONS: Compared to existing central-field protocols, larger PIPR can be induced with a full-field stimulus with lower intensity and shorter duration, indicating that PIPR is a function of stimulus intensity, stimulus duration, and retinal area stimulated. The testing protocol can be refined with this new knowledge to target particular clinical populations.

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Full-field Chromatic Pupillometry for the Assessment of the Postillumination Pupil Response Driven by Melanopsin-Containing Retinal Ganglion Cells

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