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Jason C Park, Heather Moss, J Jason McAnany; Abnormal chromatic pupillary light reflexes in idiopathic intracranial hypertension. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4547.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate rod-, cone-, and melanopsin-mediated pupillary light reflexes (PLRs) as indices of neural dysfunction in patients with idiopathic intracranial hypertension (IIH).
PLRs elicited by full-field, brief-flash (1 second) stimuli were recorded from 13 IIH patients and 13 age-similar, visually-normal controls. Subjects were tested under three paradigms intended to target the melanopsin, rod, and cone pathways. Under the melanopsin- and rod-mediated paradigms, subjects were first dark-adapted for 10 minutes and PLRs were recorded in response to short-wavelength flashes at two luminance levels (0.001 cd/m2: rod condition; 450 cd/m2: melanopsin condition). Under the cone-mediated paradigm, subjects were exposed to a rod-suppressing field and the PLR was recorded in response to 10 cd/m2 long-wavelength flashes. PLRs were quantified as the maximum transient constriction (rod and cone paradigms) and the post-illumination pupil response (PIPR; melanopsin paradigm), relative to the baseline pupil size. The ability to distinguish controls from patients based on PLR amplitude was evaluated using receiver operating characteristic (ROC) analysis.
The IIH patients had significantly smaller PLRs under the melanopsin (p < 0.001, 13% mean reduction) and rod (p = 0.04, 6% mean reduction) paradigms; a trend for reduced cone-mediated PLRs was also found (p = 0.08, 5% mean reduction). ROC analysis indicated areas under the curves (AUC) of 0.83 (melanopsin-meditated; p = 0.001), 0.71 (rod-mediated; p = 0.07), and 0.77 (cone-mediated; p = 0.02). Averaging the PLR amplitudes measured under the three paradigms for each subject resulted in a high AUC (0.90, p < 0.001), good sensitivity (85%), and good specificity (85%).
The PLR reductions in patients who have IIH indicate compromised retinal ganglion cell function and a possible role for outer-retina dysfunction. PLR measurement, particularly under rod- and melanopsin-mediated conditions, may be a useful adjunct to standard clinical measures of visual function in IIH.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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