Abstract: Objective To explore the mechanism for immediate IOP effects that occur from a single dose of latanoprost. Design One-factor repeated-measures design. Participants 15 eyes with primary open angle glaucoma were treated naively with latanoprost. Methods Intraocular pressure (IOP) and video imaging of aqueous vein were captured before and 10-min, 30-min, 45-min, 60-min, 120-min and 240-min after instillation of latanoprost. Main Outcome Measures IOP, aqueous stratum diameter (ASD) and aqueous velocity (AV). Results Before medication instillation, IOP was (28.3±4.2) mmHg. It started to dramatically decrease to (24.3±2.3) mmHg after 120 minutes (F=10.203, P=0.006). Before medication instillation, ASD was ( 0.019±0.010) μm. It started to dramatically increase to (0.034±0.007) μm after 45 minutes (F=26.187, P<0.001), which kept increasing to (0.050±0.012) μm until 60 minutes afterwards (F=20.723, P<0.001). Before medication instillation, AV was (2.1±0.5) μl/s. It started to dramatically increase to (2.6±0.6) μl/s after 30 minutes (F=5.757, P=0.031), which kept increasing to 4.3±0.9 μl/s at 45-minute and (4.3±0.9) μl/s at 60 minutes as well (F30-45=8.512, P30-45=0.011; F45-60=6.719, P45-60=0.021). Conclusion Latanoprost increase aqueous through trabecular meshwork pathway resulting immediate IOP drop. (Ophthalmol CHN, 2024, 33: 257-260)

Key words: latanoprost, intraocular pressure, aqueous stratum diameter, aqueous velocity