Study on Handheld Chromatic Pupillometry in Glaucoma Detection

Singapore: Results from a proof-of-concept study have shown handheld chromatic pupillometry (HCP) to be helpful in accurate, rapid, and objective detection of functional loss in glaucoma patients. The study was published in the British Journal of Ophthalmology.

Early detection and treatment of glaucoma can delay vision loss. However, its diagnosis often occurs at a late stage, especially in low-income and middle-income countries, where up to 50% of patients are already blind in one eye at presentation.

Chromatic pupillometry has become increasingly recognized as an effective method for evaluating retinal and optic nerve health. The device measures the pupillary responses to light stimulations of different wavelengths.

Raymond P Najjar, Visual Neurosciences Research Group, Singapore Eye Research Institute, Singapore, and colleagues aimed to evaluate the pupillary responses to exponentially increasing blue and red light stimulations in patients with different severities of glaucoma using a custom-built handheld pupillometer.

The researchers enrolled 149 patients (median age: 68.5 years) with confirmed glaucoma and 173 healthy controls (55.2 (26.7) years). They monocularly assessed changes in pupil size in response to 9 seconds of exponentially increasing blue (469 nm) and red (640 nm) light-stimuli using a custom-built handheld pupillometer. Pupillometric features were extracted from individual traces and compared between groups.

Features with the highest classification potential, selected using a gradient boosting machine technique, were incorporated into a generalized linear model for glaucoma classification. Receiver operating characteristic curve analyses (ROC) were used to compare the performance of HCP, optical coherence tomography (OCT), and Humphrey Visual Field (HVF).

Study Findings

• Pupillary light responses were altered in glaucoma compared with controls.
• For glaucoma classification, HCP yielded an area under the ROC curve (AUC) of 0.94, a sensitivity of 87.9%, and specificity of 88.4%.
• The classification performance of HCP in early-moderate glaucoma (visual field mean deviation (VFMD) > -12 dB; AUC=0.91) was similar to HVF (AUC=0.91) and reduced compared with OCT (AUC=0.97).
• For severe glaucoma (VFMD ≤ -12 dB), HCP had an excellent classification performance (AUC=0.98) that was similar to HVF and OCT.

"Our findings highlight the feasibility and high accuracy of chromatic pupillometry delivered using a handheld device for the objective detection of functional loss in glaucoma in a clinical setting," wrote the authors. Still, there is a need for community-based or opportunistic screening studies, as well as cost-effectiveness analyses to confirm whether HCP is a useful tool for glaucoma screening.

Reference

Najjar RP, Rukmini AV, Finkelstein MT, et al. Handheld chromatic pupillometry can accurately and rapidly reveal functional loss in glaucoma. British Journal of Ophthalmology Published Online First: 01 December 2021. doi: 10.1136/bjophthalmol-2021-319938