A New Pupil Light Reflex Test for Detecting Optic Neuropathy Independent of the Fellow Eye Which Highly Correlates to Visual Field Volume

Abstract

Purpose: Our purpose was to develop and test a new paradigm for detecting optic nerve disease in one eye, independent of the fellow eye, so that patients with bilateral involvement can be diagnosed and monitored using objective pupil responses. We also sought to determine which stimulus light condition and pupil response parameter (transient vs. sustained contraction) would provide the greatest difference between normal and abnormal eyes and the highest correlation with visual field sensitivity.

Methods: 39 patients seen in the neuro-ophthalmology clinic and 44 normal subjects were prospectively tested by computerized pupillometry (NeurOptics DP2000, Irvine, CA) using a 1 second red or blue light stimulus at 1 lux and 400 lux. The percent pupil contraction from baseline pre-stimulus size was calculated for the transient, initial response to the light stimulus and the sustained pupil contraction at 6 seconds following offset of light. Visual fields were obtained using standard kinetic Goldmann perimetry and the volume of visual field sensitivity was determined and correlated with pupil responses.

Results: We found the greatest statistically significant separation between eyes of normal subjects vs. those with optic neuropathy occurred with the transient pupil contraction using the 1 second, 400 lux blue light, compared to the sustained post-illumination contraction. In response to 400 lux blue light, the transient contraction gave the highest correlation with volume visual field (r=0.85) compared to the sustained contraction (r=0.52).

Conclusions: The transient pupil contraction to bright blue light provides an objective, easily recordable reflex, which correlates well with visual field sensitivity. Under these stimulus conditions, both photoreceptor input and direct activation of photosensitive retinal ganglion cells summate the visual field input to the brain. This approach provides a clinical tool for estimating visual dysfunction that has important applications for remote diagnosis and monitoring of vision threatening disorders.