The intrinsically photosensitive retinal ganglion cell (ipRGC) mediated pupil response in young adult humans with refractive errors

Jan 6, 2021Journal of optometry

Pupil responses controlled by light-sensitive eye cells in young adults with vision problems

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Abstract

A significant decrease in pupil response was observed, with lower 6 s and 30 s PIPR values for blue light compared to red light (p < 0.001).

The post-illumination pupil response (PIPR) is used to measure activity in intrinsically photosensitive retinal ganglion cells (ipRGCs).
A strong response from ipRGCs was indicated by larger early and late area under the curve (AUC) values for 1 s blue light compared to red light (p < 0.001).
Longer blue light exposure (5 s) resulted in a slightly stronger melanopsin response than shorter exposure (1 s).
No significant differences in PIPR metrics were found between myopic and non-myopic participants (p > 0.05).
Previous findings that refractive error does not affect PIPR were confirmed.

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PURPOSE: The intrinsically photosensitive retinal ganglion cells (ipRGCs) signal environmental light, with axons projected to the midbrain that control pupil size and circadian rhythms. Post-illumination pupil response (PIPR), a sustained pupil constriction after short-wavelength light stimulation, is an indirect measure of ipRGC activity. Here, we measured the PIPR in young adults with various refractive errors using a custom-made optical system.

METHODS: PIPR was measured on myopic (-3.50 ± 1.82 D, n = 20) and non-myopic (+0.28 ± 0.23 D, n = 19) participants (mean age, 23.36 ± 3.06 years). The right eye was dilated and presented with long-wavelength (red, 625 nm, 3.68 × 10photons/cm/s) and short-wavelength (blue, 470 nm, 3.24 × 10photons/cm/s) 1 s and 5 s pulses of light, and the consensual response was measured in the left eye for 60 s following light offset. The 6 s and 30 s PIPR and early and late area under the curve (AUC) for 1 and 5 s stimuli were calculated. 14 2 14 2

RESULTS: For most subjects, the 6 s and 30 s PIPR were significantly lower (p < 0.001), and the early and late AUC were significantly larger for 1 s blue light compared to red light (p < 0.001), suggesting a strong ipRGC response. The 5 s blue stimulation induced a slightly stronger melanopsin response, compared to 1 s stimulation with the same wavelength. However, none of the PIPR metrics were different between myopes and non-myopes for either stimulus duration (p > 0.05).

CONCLUSIONS: We confirm previous research that there is no effect of refractive error on the PIPR.

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The intrinsically photosensitive retinal ganglion cell (ipRGC) mediated pupil response in young adult humans with refractive errors

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