Comparing pupil function with visual function in patients with Leber's hereditary optic neuropathy

PURPOSE. To compare pupil function with visual function in patients with Le ber's hereditary optic neuropathy (LHON) and age-matched normal control sub jects. METHODS. Visual function was assessed by measuring the perceptual threshold s at five central locations in the visual field using automated static peri metry. Pupil function was assessed by recording the pupil responses to a st andard intensity light stimulus (size equivalent to a Goldmann V target) pr esented at the same five locations in the visual field. The extent of the p upil afferent defect in LHON patients was quantified by establishing the re lationship between stimulus intensity and the size of the pupil response in normal subjects and then interpolating the equivalent luminance deficit in LI-ION patients from the size of their pupil responses. RESULTS. At all five locations tested, the pupil responses were significant ly reduced in amplitude, and the perceptual thresholds were significantly r aised in LHON patients compared with normal control subjects. A nonparametr ic analysis of perceptual and pupil responses to perithreshold stimuli show ed that a stimulus that was not perceived was three times more likely to be followed by a pupil response in a LHON patient than in a normal subject (P < 0.001). A quantitative comparison showed that the visual deficits exceed ed the pupil deficits by on average 7.5 dB at all tested locations. CONCLUSIONS. Although both visual and pupil function are abnormal in LI-ION , there appears to be relative sparing of the pupil efferent fibers.