Association between melanopsin gene polymorphism (I394T) and pupillary light reflex is dependent on light wavelength

Oct 15, 2013Journal of physiological anthropology

Melanopsin gene variation (I394T) is linked to pupil response depending on light color

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Abstract

Pupils of subjects with TC + CC genotypes were significantly smaller than those with the TT genotype under blue light conditions.

Significant differences in pupil size were noted under blue light (465 nm) with high intensity (15 log photons/(cm2 s)).
No significant differences in pupil size were observed under green (536 nm) and red (632 nm) light conditions.
Relative pupil constriction was greater in TC + CC genotypes compared to TT genotypes under blue and green light at high intensities.
The melanopsin gene polymorphism (I394T) may influence pupillary light reflex sensitivity based on light intensity and wavelength.
Subjects with the C allele (TC + CC) may exhibit more sensitive pupillary light responses under specific light conditions.

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BACKGROUND: Our aim was to determine the association between melanopsin gene polymorphism and pupillary light reflex under diverse photic conditions, including different intensities and wavelengths.

METHODS: A total of 195 visually corrected subjects volunteered for investigation of the melanopsin gene of single nucleotide polymorphism (SNP) of rs1079610 (I394T). The genotype groups were TT (n = 126), TC (n = 55), and CC (n = 8), and 75 of the subjects, including subjects with TT (n = 34), TC (n = 33), and CC (n = 8) participated in our experiment. Three monochromatic lights with peak wavelengths of 465 nm (blue), 536 nm (green), and 632 nm (red) were prepared, and each light was projected to the subjects with five intensities, 12, 13, 14, 14.5 and 15 log photons/(cm2 s), for one minute. The pupil size of the left eye was measured under each light condition after a 1-minute adaptation.

RESULTS: The pupils of the TC + CC genotypes (n = 38) were significantly smaller than those of the TT genotype (n = 31) under a blue (463 nm) light condition with 15 log photons/(cm2 s) (P < 0.05). In contrast, there were no significant differences under green (536 nm) and red (632 nm) light conditions. Conversely, relative pupil constrictions of the TC + CC genotypes were greater than those of the TT genotype under both blue and green conditions with high intensities (14.5 and 15 log photons/(cm2 s)). In contrast, there were no significant differences between genotype groups in pupil size and relative pupilloconstriction under the red light conditions.

CONCLUSIONS: Our findings suggest that the melanopsin gene polymorphism (I394T) functionally interacts with pupillary light reflex, depending on light intensity and, particularly, wavelength, and that under a light condition fulfilling both high intensity and short wavelength, the pupillary light response of subjects with the C allele (TC + CC) is more sensitive to light than that of subjects with the TT genotype.

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Association between melanopsin gene polymorphism (I394T) and pupillary light reflex is dependent on light wavelength

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