Abstract
Purpose :
To evaluate rod-, cone-, and melanopsin-mediated pupillary light reflexes (PLRs) as indices of neural dysfunction in patients with idiopathic intracranial hypertension (IIH).
Methods :
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.
Results :
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%).
Conclusions :
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.