Abstract
Purpose :
To study ocular surface temperature before and after the instillation of perfluorohexyloctane (PFHO) in tear-deficient guinea pigs.
Methods :
Four young guinea pigs of both sexes were studied 4 weeks after surgical removal of the main lachrymal gland to induce tear-deficiency (DE). Infrared video images were obtained (IR thermal camera InfRec R300SR, Nippon Avionics) and analyzed using dedicated software. Ocular surface temperature was measured in the center of the cornea (CST) and the temporal conjunctiva (CJST), immediately after eye opening (T0) and 5 (T5) and 10 (T10) seconds afterwards. Slopes of temperature decay (T0/T5 and T0/T10) were also calculated. Temperature measurements were done before and 2 and 10 min after a single 10µl drop of PFHO. Tearing rate was also measured using phenol red threads placed in the nasal canthus for 30 s. The same measurements were done in 4 control animals in order to compare the data.
Results :
Before PFHO, CST was slightly higher in DE than in control animals (Table 1). PFHO treatment evoked a transient increase of blinking and a slightly increased the tearing rate in DE and control animals. CST was significantly decreased at 2 and 10 min after PFHO treatment both in control and DE animals (Table 1). T0/T5-CST slope was faster in PFHO-treated eyes (-0.06±0.02°C/s vs -0.20±0.01°C/s, p<0.05). CJST was also higher in DE than in control eyes (p<0.05). PFHO reduced CJST ~1.5°C, to values similar to those of control eyes.
Conclusions :
Perfluorohexyloctane forms a protective layer over the tear film that maintains the cornea and the conjunctiva cooler at least 10 min after its application. Reduced ocular surface temperature acts probably as a sustained stimulus for cold thermoreceptors involved in maintaining basal tearing.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.