Effect of Topical Unoprostone on Circulation of Human Optic Nerve Head and Retina

Abstract

The purpose of the present study was to study the effect of topical unoprostone on the circulation of human optic nerve head (ONH) and retina in normal subjects. Using laser-speckle tissue blood flow analysis, normalized blur (NB), a quantitative index of tissue blood velocity, was measured every 0.125 sec at a temporal ONH site, free of visible surface vessels. Measurements were averaged for 3 cardiac cycles (NB_ONH). Color Doppler imaging (CDI) was also used to evaluate peak systolic blood velocity (PSV), enddiastolic velocity (EDV), and resistive index (RI) in the central retinal artery (CRA) and mean blood velocity (MV) in the central retinal vein (CRV). For baseline comparison (Day 0), recordings of bilateral NB_ONH and intraocular pressure (IOP), blood pressure (BP), and pulse rate (PR) were recorded in healthy volunteers before, and 45, 90, 180, and 270 min after instillation of one drop of unoprostone vehicle. On Day 1 (the day after baseline measurements), and twice daily for 7 days, one drop of 0.12% unoprostone was instilled into one eye and its vehicle into the other in a double-blinded manner. Measurements as on Day 0 were recorded on Days 1 and 7. CDI measurements were performed before and at 45 and 180 min after morning instillation on Days 1 and 7. During baseline recordings, there were no significant changes in any parameters. After administration of topical unoprostone, IOP was significantly lower bilaterally with more reduction in the unoprostone-treated eyes on Day 7. On Day 7, the NB_ONH of the unoprostonetreated eyes was significantly higher 45 min after instillation than baseline (P = 0.035 with Bonferroni's correction). Analysis of variance for repeated measurements also revealed significant difference between Day 0 and Day 7 (P = 0.0017). BP, PR, NB_ONH in the eye that received only the vehicle, PSV, EDV, and RI in the CRA in both eyes, and MV in the CRV in both eyes changed little. Tissue blood velocity in the ONH increased, at least temporarily, following instillation of unoprostone twice daily for 7 days. Although the clinical implication of the increase is unclear, the effects of topical unoprostone on human ONH circulation deserve further consideration.