Use of tear secretion and tear film to screen potential dry eyes in a cynomolgus monkey population

Abstract

Purpose : Dry eye disease is a complex eye problem that affects life quality of a large number of people and therefore require more innovative medication. Translatable disease models such as non-human primates (NHPs) models would greatly benefit the development of new medications. Currently there are limited reports of dry eye disease in NHPs. In this study we screened potential dry eyes of a large monkey colony by using the tear secretion (Schirmer I test) and tear film stability (FBUT) and explored the effects of measurement procedure on the results.

Methods : A total of 220 cynomolgus monkeys (aged 8.8 to 23.7y, 14.6y in average) were enrolled in current study as following: Group 1 (n=63) had Schirmer I test (without topical anesthesia) and tear break-up time (FBUT; n=50). Group 2 (n=68) had Schirmer I test (with topical anesthesia) and FBUT. Group 3 (n=89, 178 eyes) had only FBUT. For both Group 1 and Group 2, FBUT was tested after Schirmer I test. All animals had general anesthesia with or without topical anesthesia in both eyes of each animal. Schirmer I test≤5 mm and/or FBUT≤5 mm/min for each eye were used as diagnostic criteria for potential dry eyes for further ocular examinations (Fujita M, et al. 2005).

Results : (1). The incidences of dry eyes were 8 (16 %) and 14 (20.6 %) in Group 1 and 2 respectively when both Schirmer I test≤5 mm and FBUT≤5 mm/min were included as selection criteria. The incidences became 47 (74.6 %), 61 (89.7%) and 61 (68.5%) in the groups when either Schirmer I test≤5 mm or FBUT≤5 mm/min were used as the criteria. (2) In the 220 monkeys there were 2 monkeys which had Schirmer I test ≤2 mm (possible aqueous tear deficiency), and 51 monkey which had FBUT≤5 s and Schirmer I 5~10 mm (possible lipid deficiency) (Messmer EM. 2015). (3). Schirmer I test was higher in Group 1 (without topical anesthesia) than Group 2 (with topical anesthesia), while FBUT was not different between the groups. (4). FBUT was significantly shorter in Group 2 (Schirmer I test followed FBUT) than Group 3 (FBUT alone).

Conclusions : Schirmer I test and FBUT can be used as screening tools for identifying monkey dry eyes. Some procedures must be considered to decrease their effects on testing results.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.