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Choroideremia: melanopsin‐mediated postillumination pupil relaxation is abnormally slow
Author(s) -
BaAli Shakoor,
Christensen Søren Kirchhoff,
Sander Birgit,
Rosenberg Thomas,
Larsen Michael,
LundAndersen Henrik
Publication year - 2017
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/aos.13394
Subject(s) - melanopsin , choroideremia , pupillary response , pupillometry , pupil , ophthalmology , intrinsically photosensitive retinal ganglion cells , nystagmus , retinal , medicine , blue light , pupillary light reflex , optics , audiology , physics , photopigment , retinal ganglion cell
Abstract Purpose To investigate the rod–cone and melanopsin pupillary light response (PLR) pathways in choroideremia. Methods Eight patients with choroideremia and 18 healthy age‐matched controls underwent chromatic pupillometry by applying blue (463 nm) and red light (643 nm) at 100 lux intensity to the right eye while recording pupil diameters. Absolute baseline pupil size (mm), normalized maximal pupil constriction and the early and late postillumination pupillary dilation, from 0 to 10 seconds and 10 to 30 seconds after the end of illumination, respectively, were determined. Postillumination responses to blue light were considered to be primarily driven by melanopsin activation of the intrinsic photosensitive retinal ganglion cells. Results Baseline pupil diameters were comparable in patients with choroideremia and control subjects (p = 0.48). The maximum pupil constriction in patients with choroideremia was severely weakened in red light but only mildly weakened in blue light (p < 0.05). Postillumination dilation of the pupil was normal after red illumination but extremely protracted after blue illumination. Also, in contrast to healthy subjects, no abrupt change in the dilation curve was seen in the patients after the end of blue illumination, the early‐phase dilation being completely abolished (p < 0.01). Conclusion Rod–cone‐driven pupil responses were decreased as expected in an outer retinal degeneration, and near‐normal pupil constriction in blue light supports that the melanopsin system is normal. In contrast, the lack of brisk early‐phase dilation after blue illumination in choroideremia is remarkable and may be interpreted to mean that the absence of photoreceptor inhibition promotes a tonic contraction of the pupil.