Chromatic pupil responses: preferential activation of the melanopsin-mediated versus outer photoreceptor-mediated pupil light reflex.
OBJECTIVE
To weight the rod-, cone-, and melanopsin-mediated activation of the retinal ganglion cells, which drive the pupil light reflex by varying the light stimulus wavelength, intensity, and duration.


METHODS
Experimental study.


METHODS
Forty-three subjects with normal eyes and 3 patients with neuroretinal visual loss.


METHODS
A novel stimulus paradigm was developed using either a long wavelength (red) or short wavelength (blue) light given as a continuous Ganzfeld stimulus with stepwise increases over a 2 log-unit range. The pupillary movement before, during, and after the light stimulus was recorded in real time with an infrared illuminated video camera.


METHODS
The percent pupil contraction of the transient and sustained pupil response to a low- (1 cd/m(2)), medium- (10 cd/m(2)), and high-intensity (100 cd/m(2)) red- and blue-light stimulus was calculated for 1 eye of each subject. From the 43 normal eyes, median and 25th, 75th, 5th, and 95th percentile values were obtained for each stimulus condition.


RESULTS
In normal eyes at lower intensities, blue light evoked much greater pupil responses compared with red light when matched for photopic luminance. The transient pupil contraction was generally greater than the sustained contraction, and this disparity was greatest at the lowest light intensity and least apparent with bright (100 cd/m(2)) blue light. A patient with primarily rod dysfunction (nonrecordable scotopic electroretinogram) showed significantly reduced pupil responses to blue light at lower intensities. A patient with achromatopsia and an almost normal visual field showed selective reduction of the pupil response to red-light stimulation. A patient with ganglion cell dysfunction owing to anterior ischemic optic neuropathy demonstrated global loss of pupil responses to red and blue light in the affected eye.


CONCLUSIONS
Pupil responses that differ as a function of light intensity and wavelength support the hypothesis that selected stimulus conditions can produce pupil responses that reflect phototransduction primarily mediated by rods, cones, or melanopsin. Use of chromatic pupil responses may be a novel way to diagnose and monitor diseases affecting either the outer or inner retina.
Kardon
Randy
R
Department of Ophthalmology and Visual Science, University of Iowa, USA.
Anderson
Susan C
SC
Damarjian
Tina G
TG
Grace
Elizabeth M
EM
Stone
Edwin
E
Kawasaki
Aki
A
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D018917:Optic Neuropathy, Ischemic / Q000378:metabolism; D010781:Photography; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism; D011680:Pupil / Q000528:radiation effects*; D012025:Reflex, Pupillary / Q000528:radiation effects*; D012162:Retinal Degeneration / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000378:metabolism; D055214:Retinal Photoreceptor Cell Outer Segment / Q000378:metabolism* / Q000528:radiation effects*; D017299:Rod Opsins / Q000378:metabolism*; D055815:Young Adult; D000099210:Melanopsin
D017299:Rod Opsins; D000099210:Melanopsin