The diagnostic accuracy of chromatic pupillary light responses in diseases of the outer and inner retina.

Purpose: To compare the chromatic pupillary light responses (PLR) in healthy subjects with those from patients with diseases of the outer or inner retina under various stimulus conditions, and to ascertain the parameters required to optimally distinguish between disease and control groups.
Methods: Fifteen patients with retinitis pigmentosa (RP), 19 patients with optic nerve disease (ON), and 16 healthy subjects were enrolled in this prospective study. ON included optic neuritis (NNO) and non-arteritic anterior ischemic optic neuropathy (NAION). For each subject, the PLR was recorded, to red, yellow, green, and blue stimuli for durations of 4 and 12 s, and for stimulus intensities of 4 lx and 28 lx.
Results: Comparison between control and RP or ON patient results showed that responses after stimulus onset were significantly different for most stimulus conditions, but the post-stimulus amplitudes at 3 s and 7 s after light extinction were not. On the other hand, the difference between the ON and RP groups was significant only for post-stimuli time-points and only for blue stimuli. Differences between responses to blue and red were significantly different, predominantly at post stimulus time-points. A ROC analysis revealed that the maximal constriction amplitudes to a 4 lx, 4 s yellow stimulus are significantly different in ON vs RP patients, and the responses to a 4 s, 28 lx blue stimulus at 7 s post-stimulus are significantly different in controls vs ON vs RP patients with a high specificity.
Conclusions: Pupillary light responses to blue light in healthy, RP, and ON subjects are significantly different from one another. The optimal stimuli for future protocols was found to be a 4 s blue stimulus at 28 lx, and a 4 s yellow stimulus at 4 lx.