Abstract
PurposeTo examine systematically how prechiasmal, chiasmal, and postchiasmal lesions along the visual pathway affect the respective pupillary responses to specific local monochromatic stimuli.MethodsChromatic pupil campimetry (CPC) was performed in three patient groups (10 subjects with status after anterior ischemic optic neuropathy, 6 with chiasmal lesions, and 12 with optic tract or occipital lobe lesions (tumor, ischemia)) using red, low-intensity red, and blue local stimuli within the central 30° visual field. Affected areas - as determined by visual field defects revealed using conventional static perimetry - were compared with non-affected areas. Outcome parameters were the relative maximal constriction amplitude (relMCA) and the latency to constriction onset of the pupillary responses.ResultsA statistically significant relMCA reduction was observed in the affected areas of postchiasmal lesions with red (p = 0.004) and low-intensity red stimulation (p = 0.001). RelMCA reduction in the affected areas seemed more pronounced for low-intensity red stimulation (46.5% mean reduction compared to non-affected areas; 36% for red stimulation), however statistically not significant. In prechiasmal lesions, a statistically significant latency prolongation could be demonstrated in the affected areas with low-intensity red stimulation (p = 0.015).ConclusionOur results indicate that the choice of stimulus characteristics is relevant in detecting defects in the pupillary pathway of impairment along the visual pathway, favoring red stimuli of low intensity over blue stimuli. Such knowledge opens the door for further fundamental research in pupillary pathways and is important for future clinical application of pupillography in neuro-ophthalmologic patients.
Highlights
Color pupillography is a useful, objective, and non-contact method for determining retinal function in certain retinal diseases
Mean relative maximal constriction amplitude (relMCA) and latencies from all affected areas - as categorized by visual field defects - were calculated per group and per stimulation characteristic and compared with the respective mean pupillary responses from all non-affected areas from all participants
Whereas retinal defects are quite precisely detectable by pupillography, inconsistent results are reported in the literature with regard to defects in the subsequent visual pathway via the optic nerve, optic tract, and visual cortex
Summary
Color pupillography is a useful, objective, and non-contact method for determining retinal function in certain retinal diseases. Spatial pupillographic strategies, such as chromatic pupil campimetry (CPC) [5, 6], are of increasing importance, as they objectively provide information of local functionality for natural history observations as well as follow-up after therapeutic intervention in patients with specific retinal diseases. E.g., rod-cone dystrophies or age-related macular degeneration, are precisely detectable by CPC [6,7,8,9]. This raises the question how do defects in the subsequent network of the visual pathway affect pupillary responses? Bremner et al proposed different visual and pupillary pathways with a “pupil sparing” in hereditary optic neuropathies such as Leber hereditary optic neuropathy (LHON) and autosomal dominant optic atrophy (ADOA) (i.e., pupil reaction is relatively better preserved than the visual field) and a “visual sparing” in demyelinating optic neuritis (i.e., visual field is relatively less affected than the pupil reaction) [17]
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