In a new research paper from LVPEI, Rahul Negi, Dr. Shrikant R. Bharadwaj, and others describe the development and efficacy of a modularized virtual reality-based automated pupillometer for diagnosing optic neuropathies in one eye.
The pupil—the aperture-like opening at the center of our eyes—constricts when exposed to bright light and dilates in dim light to control the amount of light entering the eye. This response typically occurs in unison across both eyes. Optic neuropathies, disorders that arise from a damaged optic nerve, are marked by defects in how our eyes respond to light. In unilateral optic neuropathies (only one eye has optic nerve damage), this reflex is impaired in the affected eye, resulting in a phenomenon called relative afferent pupillary defect (RAPD). Traditionally, RAPD is diagnosed using the ‘swinging light test,’ where a flashlight is swung back and forth between the affected and unaffected eye. This process relies on the clinician's subjective judgment and is significantly influenced by the testing conditions.
Automated pupillometers standardize the testing conditions, making the test outcomes more reliable. However, these devices are costly and have limited applicability. Nowadays, Virtual reality (VR) headsets are used in many hospitals to assess visual functions, monitor eye diseases, and to treat amblyopia (lazy eye) in children using ‘video-game therapy’. Integrating eye trackers into VR headsets can turn them into an automated pupillometer without the need to buy an expensive, dedicated device. But would such a modular system be accurate enough to match a dedicated pupillometer?
In a new research paper published in the journal Frontiers in Ophthalmology, Rahul Negi, Dr. Shrikant R. Bharadwaj, and others from LVPEI describe the development and efficacy of a modular VR-based automated pupillometer. The researchers took the Pupil+®, a dedicated pupillometer developed at LVPEI, and modularized it such that it can be integrated into a commercially available VR headset (Pico Neo 2 Eye®) with built-in eye tracking capability. The device was used to diagnose RAPD in 77 patients with a variety of unilateral optic neuropathies and 77 age-matched controls (people with no optic neuropathy). The RAPD patients were also independently assessed by experienced neuro-ophthalmologists.
Among patients with neuropathies, the median pupil constriction in the affected eye was 38% weaker than the unaffected eye. In contrast, the difference in pupil constriction between the eyes of controls was only 6%. The device was initially able to detect RAPD with a sensitivity of 78.5% and a specificity—the ability to detect false positives—of 87%. Physiological differences can exist in the visual pathways of an individual. This can cause a pupillometer to give a false reading. When the researchers accounted for these differences, the sensitivity of the VR device increased to 85.1% and the specificity increased to 89.7%. These values fall within the gold standard for RAPD detection. The modular VR-based automated pupillometer proved to be an effective, bias-free device that can be a viable alternative to a dedicated pupillometer.
'This study demonstrates two things, using the pupillary assessment as a use-case for the battery of tests in a comprehensive eye exam,' explains Dr. Shrikant R. Bharadwaj, Network Associate Director of Brien Holden Institute of Optometry and Vision Sciences, LVPEI, and the corresponding author of this paper. 'First, the subjective element in clinical tests can be minimized through standardized, objective assessment using modern-day technology. Second, the era of having dedicated devices for assessing different ocular functions is behind us; integrating multiple tests into a single modularized platform such as VR-headsets is an efficient and cost-effective way to conduct a comprehensive eye exam.'
Citation
Negi, R., Kalivemula, M., Bisht, K., Bhate, M., Sachdeva, V., & Bharadwaj, S. R. (2024). Diagnostic accuracy of a modularized, virtual-reality-based automated pupillometer for detection of relative afferent pupillary defect in unilateral optic neuropathies. Frontiers in Ophthalmology, 4, 1396511. https://doi.org/10.3389/fopht.2024.1396511
