Development and Implementation of a Handheld Pupillometer for Detection of Optic Neuropathies

ABSTRACT

Purpose: Quantitative pupillometry has utility in research settings for measuring optic nerve and autonomic function. We configured a portable device to perform quantitative pupillometry with application to detecting unilateral optic neuropathies in the clinical setting.

Materials & methods: Light stimuli were delivered, and pupil diameter responses recorded using customized software implemented on a commercial portable electroretinography device. Increasing pupillary constriction occurred with increasing duration and intensity of full field blue light (470 nm) stimuli in healthy subjects. Flashes of 1 s dim (50 cd/m²) and bright (316 cd/m²) blue light were administered to both eyes of subjects with unilateral optic neuropathies (n = 10) and controls (n = 5). Maximum pupillary constriction (C_max) for each stimulus was compared between control eyes and optic neuropathy eyes. C_max for the inter-eye difference curve (C_diffmax) was compared between control and optic neuropathy subjects.

Results: The pupil protocol lasted 15 minutes and was well tolerated by subjects. C_max for bright and dim stimuli was reduced in eyes with optic neuropathy compared to fellow and control eyes (p < .0005 for all). Inter-eye C_diffmax was larger in optic neuropathy subjects than control subjects for both dim and bright stimuli (p = .002, <0.0005). There was no overlap between groups for C_max and C_diffmax for either stimulus.

Conclusions: A portable pupillometer was implemented on a commercial portable electroretinography platform and applied in a pilot manner to subjects with and without unilateral optic neuropathies. Optic neuropathy eyes were distinguished from non-optic neuropathy eyes both within and between subjects.

KEYWORDS:

• Pupillometry
• optic neuropathies
• diagnosis
• validation
• pupillary light response
• afferent pupillary defect

Declaration of interest statement

LKC Inc provided the retEVAL device for research use, but had no input in the research planning, performance, interpretation or manuscript. There are no other relevant financial or non-financial competing interests to report.

Data availability statement

The data that support the findings of this study are available from the corresponding author, [HEM, [email protected]], upon reasonable request.

Additional information

Funding

This work was supported by the National Eye Institute (National Institutes of Health) under [K23 EY 024345 and NIH P30 EY 026877]; and Research to Prevent Blindness under an unrestricted grant to Stanford Department of Ophthalmology.