Abstract
Purpose :
To analyze whether tear volume changes induced by ocular inflammation or instillation of warm saline solution affect corneal surface temperature (CST) values in guinea pigs.
Methods :
Young guinea pig eyes of both sexes were used in the study. Tear volume was measured as the mm of wet phenol red threads applied on the lower lid for 30s. CST was measured from infrared video images taken with an infrared video camera. Temperature value immediately after eye opening and its change during the following 10 seconds were analyzed using dedicated software. In a group of guinea pigs previously sensitized to ovalbumin, experimental parameters were obtained at basal condition and after inducing allergic keratoconjunctivitis (AK) by ocular application of ovalbumin. In a separate group of naïve animals, measures were performed in basal conditions and after increasing the aqueous component of the tear film by topical application of different volumes (5-10 μl drops) of saline solution warmed up to 37oC avoid changing the temperature of the cornea (mean basal value: 36.5±0.1oC).
Results :
During AK, all the animals presented conjunctival hyperemia, and significant increase in tear volume (+10.3±3.8 mm, n=6; p<0.05) and CST values (+0.25±0.12oC; p<0.01). When the aqueous component of the tear film was artificially increased in naïve guinea pigs by instillation of warm saline tear volume increased significantly (+14.8±1.9 mm and +21.0±2.1 mm, for of drops of 5 and 10 μl, respectively; p<0.001), and CST values decreased between 0.14o and 0.96oC, proportionally to the drop volume (r=-0.405, Pearson correlation coefficient, p<0.05).
Conclusions :
Corneal surface temperature increases during ocular allergic keratoconjunctivitis, probably due to the conjunctival and limbal hyperemia induced by inflammation. The corneal surface temperature values obtained by infrared thermography in this condition may be underestimated because surface temperature values seem to be affected by the amount of liquid over the cornea. The influence of tear volume on corneal surface temperature values should be considered when using infrared thermography as a complementary tool in ocular surface disorders diagnosis.
This is a 2021 ARVO Annual Meeting abstract.