Infrared thermography used to measure the temperature of the ocular surface is gaining steam as a way to evaluate the ocular surface, and this quick, noninvasive test is reported to cause minimal, if any, discomfort. Looking further into its potential, a research team from the Bascom Palmer Eye Institute and the Miami Veterans Affairs Medical Center suggests ocular surface temperature could offer valuable insight into the health of the ocular surface and even be used to diagnose dry eye.
The study reviewed current literature to evaluate the relationship between ocular surface temperature and tear film parameters.
The ocular surface temperature of the central cornea is normally around 35°C when measured right after a blink and decreases at a rate of -0.01°C per second in healthy eyes, the researchers explained. More specifically, each blink “resets” the ocular surface temperature through heat exchange with the inner eyelid to its maximum temperature, while the eye subsequently cools between blinks as it is exposed to the environment.
The team reported that ocular surface temperature cooling over the inter-blink period appeared to be tied to tear parameters including Schirmer’s test scores, tear meniscus height and tear film breakup time. They also found that ocular surface temperature was higher in eyes with a more unstable tear film.
“When examining ocular surface temperature cooling rate, an unstable tear film, a larger quantity of tears and increased blink frequency were all associated with greater decreases in ocular surface temperature over time,” the researchers wrote in their paper. Given that an unstable tear film is one key component in dry eye, ocular surface temperature could be used to screen for this condition, but future studies are needed, they added.
Shah AM, Galor A. Impact of ocular surface temperature on tear characteristics: current insights. Clin Optom (Auckl). 2021;13:51-62.