The evaluation of the effect of tafluprost on the intraocular pressure of healthy male guinea pigs under different light‐and‐darkness regimes

Background Ocular hypertension is one of the most underdiagnosed ocular abnormalities among guinea pigs around the world. Objectives The current study investigates the effect of 0.0015% preservative‐free tafluprost ophthalmic solution (Zioptan) on the intraocular pressure of 16 healthy male guinea pigs (Cavia porcellus) under different light/darkness regimes. Methods All guinea pigs received a single drop of tafluprost at 5:30 in the right eye, whereas the contralateral eyes served as control to receive a placebo. Then, the animals were randomly divided into two groups; group A was exposed to light, whereas group B was placed in darkness from 5:30 to 18:00. Rebound tonometry (TonoVet) was instrumented to measure IOP values at 5:30 (baseline), 6:00, 7:00, 8:00, 9:00 and then every 3 h until 18:00. Results The maximum IOP reduction associated with tafluprost was observed at 6:00 by −1.4 ± 1.1 mmHg (p‐value = 0.026) and −2.5 ± 1.2 mmHg (p‐value = 0.011) in group A and B, respectively (repeated measure ANOVA test). There was a significant difference between the mean right and left eye IOP values in both groups at 5:30, 6:00, 7:00 and 8:00 (p‐value