PMN accumulation in aqueous humor and iris-ciliary body during intraocular inflammation.

The accumulation of polymorphonuclear leukocytes (PMNs) was determined in the aqueous humor and iris-ciliary body following an intravitreal injection of endotoxin in the albino rabbit. PMN accumulation in the iris-ciliary body was quantified by measuring myeloperoxidase (MPO) activity in homogenates of this tissue. Leukocyte appearance in the aqueous humor was determined by counting the number of PMNs in diluted aspirates of aqueous humor and also by measuring MPO activity in the same aspirates. Twenty-four hours following an intravitreal injection of endotoxin, there was marked vasodilatation in the iris, breakdown of the blood-aqueous barrier, and infiltration of PMNs into the aqueous humor. There was, however, no correlation between MPO activity in the iris-ciliary body and the number of PMNs or the MPO activity in the aqueous humor. Furthermore, the number of PMNs in the aqueous humor did not increase with increasing amounts of intravitreally injected endotoxin, whereas MPO activity in the iris-ciliary body increased in a dose-dependent manner. The results of this study suggest that quantification of leukocytes in the aqueous humor does not represent a meaningful index of intraocular inflammation.