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Megan Hannah Vaughan, Javier Gantes-Nuñez, Juan Tabernero, Shahina Pardhan; The post-illumination pupillary response of dark and light irides. Invest. Ophthalmol. Vis. Sci. 2020;61(7):607.
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Intrinsically photosensitive retinal ganglion cells (ipRGCs) has been shown to be reduced in a number of eye diseases. However, the normal population is yet to be fully investigated. A cross-sectional study of the ipRGCs function using the 6s Post Illumination Pupillary Response (PIPR) to blue light (480nm) in those with light and dark irides was conducted in a healthy population.
Pupil responses, PIPR and maximum constriction were measured in 90 healthy participants. PIPR is the pupil recovery 6s after light offset and maximum constriction is the initial constriction value in response to the blue light. Participants were split into two groups based on their iris colour, light: blue-green (n=50, mean age 35 ± 15.5 years) and dark: hazel-brown (n=40, mean age 30 ± 11.3 years). The pupil responses were measured using a low-cost (<GBP100) custom-built infrared pupillometer. The pupillometer comprised a 5Mp IR camera, two Infrared LEDs and four blue LEDs, controlled by a Raspberry Pi computer. Stimuli consisted of a 1.5s pulse of blue light and the right pupil was video recorded using the camera. Measurements were preceded by a period of 10 mins of dark adaptation (<5 lux). PIPR and maximum pupil constriction are expressed as a percentage baseline value (Mean ± SD). A less sustained pupil and/or reduced constriction yields a higher percentage value.
The PIPR was less sustained in those with light irides (82.0 ± 5.1%) compared to dark irides (80.4 ± 3.1%), but this was not significant (p>0.05). Maximum constriction in response to the blue (480nm) light was less in those with light irides (55.5 ± 5.7%) than those with dark irides (53.0 ± 5.2%), but, again, this difference was not significant (p>0.05).
These results further our understanding of the ipRGCs in a normal population. Iris colour does not have a significant effect on PIPR or the maximum constriction.
This is a 2020 ARVO Annual Meeting abstract.
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