Determination the reference value for measuring tear production by using the STT1 and STT2 in Caspian horse

Ocular dryness can be assessed by Schirmer's test, tear break time (TBUT), tear mucin measurement, goblet cell count as well as osmolarity, lysozyme and lactoferrin tears. Because of the simple and availability of the Schirmer's test and TBUT measurement, these two methods are more commonly used as ophthalmic examinations in ophthalmology studies. Currently, in the topical ophthalmic anesthesia routine, tetracaine is the most widely used drug that can eliminate reflex tears. The purpose of this research is to measure basal tear production in Caspian horses. In this regard, 20 apparently healthy Caspian horses, both male and female, were selected; aged between 5 to 14 years old and the mean body weight was 203 ± 38 kg. Two groups of 10 Caspian horses were randomly assigned. After physical examination and reviewing the Caspian horse's health history and consequently assurance of their health schirmer tear test (STT) performed for both eyes of all animals. In treatment group (tetracaine 0.5%) and control group (0.9% normal saline), STT repeated at 10, 20, 30, 40, 50 minutes after instillation. Comparative study of test (T) and control (C) showed us statistically significant decrease in T group and the comparative study of STT between T0 and others result of T group shows a statistically significant decrease until 40 minutes after instillation. The data were analyzed using the one-way ANOVA method. Based on the results of this study, the variants of age and gender have no significant effects on the STT1 and STT2 results in the Caspian horses. Considering the importance of rapid diagnosis of dry eye syndrome and disorders associated with basal and reflex tear production and preventing its subsequent disorders such as Keratoconjunctivitis Sicca; this survey aims to evaluate effects of topical ophthalmic use of tetracain hydrochloride 0.5% on STT results in clinically normal Caspian horses.