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L. Kankipati, P. D. Gamlin, C. A. Girkin; The Pupillary Light Offset Response Is Reduced in Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5836.
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The intrinsic photoresponse of melanopsin-containing, intrinsically photoreceptive retinal ganglion cells (ipRGCs) is most sensitive to short wavelength (~480nm) light, and underlies the sustained pupilloconstriction observed following light offset (the pupillary light offset response (PLOR)) (Gamlin et al, 2007). In glaucomatous optic neuropathy (GON), it is expected that ipRGC number will be decreased, resulting in a reduction in the magnitude of the PLOR. Therefore comparison of the magnitude of the PLOR between normal subjects and glaucomatous patients could provide an additional means for characterizing the progression and severity of this disease.
We measured the PLOR in normal subjects without ocular disease (n=38) and patients with advanced glaucoma (n=8). The stimulus was presented in Maxwellian view to one eye that was dilated with 2.5% Phenylephrine/1% Tropicamide, while the consensual pupil response of the fellow, undilated eye was recorded by an IR camera and computer. The test was conducted by presenting a 600, 10-second light stimulus of equal retinal irradiance (13 log quanta/cm2/s) at 470 nm and 623 nm, and recording the pupillary response for 50 seconds after light offset. We calculated the magnitude of the sustained pupillary constriction as the average pupil diameter for the period of 40 seconds after light cessation, and baseline as the average pupillary diameter for 7 seconds prior to light onset.
There is a significant reduction in the PLOR in advanced-stage GON patients. Along with traditional tests, this test has the potential to be used as a screening tool in glaucomatous patients. Further work is needed to evaluate the PLOR in earlier stages of GON.
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