To the Editor.
—Coagulation properties of human aqueous humor have been reported by Khodadoust et al.1 They found that aqueous humor shortened the average earlobe puncture bleeding time, as well as the prothrombin and partial thromboplastin times. Moreover, they showed that most of the coagulation factors were not responsible for this effect and concluded that a tissue thromboplastin or thromboplastinlike substance, as well as the effects on the vascular wall, needed to be investigated.Arteries and veins are strongly constricted by serotonin, and its intravenous infusion is accompanied by intense venospasm. Local vasoconstriction, or vascular spasm, is the initial step in hemostasis and this is due, in part, to serotonin liberated from platelets.2Recently, we measured a mean serotonin concentration of 50 ng/mL in the aqueous humor of patients undergoing surgery for cataract.3 This concentration is more than 500 times the concentration of epinephrine measured in human
Martin XD, Brennan MC, Lichter PR. Serotonin, Vasoconstrictor of Human Aqueous Humor. Arch Ophthalmol. 1989;107(4):488-489. doi:10.1001/archopht.1989.01070010502011