Objective Ocular Discomfort: Noninvasive Evaluation by Functional Near-Infrared Ray Spectroscopy

Patients express their discomfort by subjective complaints, which may not clearly express the extent of their discomfort. This study noninvasively and objectively quantified ocular discomfort, a form of feeling, from the prefrontal cortex by functional near-infrared ray spectroscopy topography.

This case-controlled study enrolled six dry eye patients (male:female, 1:1; 51.8 ± 15.9 years) with ocular discomfort and six normal controls (male:female, 1:1; 48.8 ± 15.2 years). Ocular discomfort was created by Schirmer 1 test in normal controls. The extent of prefrontal cortex activity was evaluated as the number of signal-positive channels using the system by using an eye-opening task with spontaneous blinking in the dark. Changes in the signal-positive channels count by lubricant or anesthetics instillation were analyzed.

Low prefrontal cortex activation was detected in normal controls without ocular discomfort, and high activation was detected in both normal controls and dry eye with ocular discomfort. Prefrontal cortex activity was confirmed with ocular discomfort when the eyes were open, decreased with lubricant, and almost disappeared with anesthetic for all participants.

These changes in the prefrontal cortex activity exhibited a significant correlation to subjective complaint scores, suggesting that such discomfort may be objectively quantifiable, independent of subjective expressions.