Effect of Light Wavelength on Corneal Sensitivity

Evaluate corneal sensitivity as a potential pathway for blue light-induced ocular discomfort.

Cross-sectional study.

Healthy adult volunteers without previous ocular medical history.

Subjects were exposed to a Hue A19 LED bulb calibrated for equivalent photo flux for 450 nm (blue) and 620 nm (red) wavelengths. Corneal sensitivity measurements via a 0.12-mm filament Cochet-Bonet esthesiometer were ascertained after 1 minute of exposure and throughout testing. The order of exposed wavelength was randomized, with a 5-minute rest interval between exposure to each wavelength of light.

Cochet-Bonnet measurements of (1) threshold to sensation, (2) discrimination, and (3) threshold to pain. Threshold to sensation was determined by the longest filament length at which the subject noted consistent initial sensation. Discrimination was determined by changing the filament length by 5-mm increments (both retraction and extension) until the subject was able to correctly and consistently distinguish less, greater, or equal sensation compared with the previous application. Threshold to pain was determined at the filament length at which the participant expressed pain or discomfort.

There was no difference in threshold to sensation between blue (450 nm) and red (620 nm) light sources (P ≥ 0.99). There was no statistically significant difference in discrimination of stimuli under blue- or red-light exposure (P = 0.30), although blue-light exposure trended to be more sensitive. The threshold to pain under blue light was statistically significantly lower than in red-light conditions, with pain at a longer filament length under blue-light exposure compared with red-light exposure (median 12.5 mm vs. 7.5 mm, respectively; P = 0.03).

Blue- versus red-light exposure decreases subjective corneal pain threshold when measured by the Cochet-Bonnet esthesiometer. Altered corneal sensitivity may mediate blue light-induced ocular discomfort. The Cochet-Bonnet esthesiometer is a useful tool in the study of blue light-induced discomfort.

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