Evaluation of D-dimer levels in aqueous humor of rabbit eyes with and without induced intraocular fibrin and fibrinolytic treatment.

OBJECTIVE: To analyze D-dimer concentrations in aqueous humor (AH) of rabbit eyes under physiological conditions, after induction of fibrin clots, and following fibrinolytic therapy. ANIMALS STUDIED: Prospective study measuring D-dimers in aqueous humor of rabbit eyes with induced fibrin clots (n = 44). PROCEDURES: Rabbits were purchased in two groups, which led to two temporally separated experimentation groups. Different treatment protocols were compared for their efficacy in fibrin reduction (slit-lamp examination, high-resolution ultrasound). AH was taken from left eyes before clot induction (baseline, day 1), 24 hours later after clot establishment/prior to drug administration (post-induction, day 2) and 48 hours after clot induction (post-treatment, day 3). An enzyme-linked immunosorbent assay (ELISA) was performed to measure intraocular D-dimer concentrations RESULTS: D-dimer concentrations were measurable in all samples. There were no differences in D-dimer levels across time points or treatments within the arrival groups. However, a significant difference in mean D-dimer levels was observed between the two arrival groups (group 1:3.1 µg/mL; group 2:6.1 µg/mL; P < .0001), which made a direct comparison of treatment groups impossible. Clinically, all eyes displayed fibrin clots in the anterior chamber and different treatment types led to significant differences in clot resolution (clot size reduction after intracameral treatment: 98%, topical treatment: 60%, no treatment: 40%). CONCLUSION: D-dimers were identified in all AH samples of rabbits with large variability between samples. D-dimer levels were neither predictive for differences in induced fibrin formation nor for drug efficacy.

Fibrinolytic Capacity of Desmoteplase Compared to Tissue Plasminogen Activator in Rabbit Eyes.

PURPOSE: Desmoteplase (DSPA) was evaluated and compared with tissue plasminogen activator (t-PA) for its intraocular fibrinolytic effect and short-term toxicity in an in vivo study using rabbit eyes. METHODS: Fibrin clots were induced in the anterior chamber of 44 rabbit eyes, and drug efficacy was measured by clot size reduction over 24 h. Topical DSPA eye drops (1.4 and 2 mg/mL) were compared with vehicle solution in a multiple-drop regimen in 8 animals per group. Intracameral injections of 0.6 µg DSPA (n = 14) and 25 µg t-PA (n = 14) were evaluated for their fibrinolytic efficacy. Animals were euthanized 24 h after drug application. RESULTS: No significant differences were seen between topically treated DSPA and vehicle-treated animals. Intracameral t-PA had a higher fibrinolytic efficacy than DSPA at early time points, but no significant difference was seen between both groups at 24-h postapplication. Animals with t-PA treatment demonstrated significantly more side effects compared with DSPA-treated animals. DSPA showed no-to-mild side effects after topical and intracameral treatment. Histologically, no toxic effects were observed in any globe. CONCLUSIONS: DSPA is a promising drug with fewer side effects and similar fibrinolytic efficacy compared with t-PA 24 h after intracameral application in rabbit eyes at the tested concentration. Drug efficacy might be improved by increasing intracameral DSPA doses.