Purpose: The aim of the present investigation was to develop a new ocular inflammation model in the rabbit by comparison of the inflammation response induced by the topical application of several irritating agents (carrageenan, Freund's adjuvant, alkali and croton oil).
Methods: The following parameters were determined after the application of each irritant to the eyes of female, white, New Zealand rabbits: Corneal edema and the Tyndall effect (slit-lamp biomicroscopy), corneal thickness (biometer-pachometer) and aqueous humor levels of the prostaglandin E2 (R.I.A), total protein (Weichselbaum technique), albumin, albumin/globulin (Doumas technique) and leukocytes (coulter counter).
Results: Croton oil 1-4% (40 microl) produced edema and a Tyndall which showed a proportional increase with croton oil concentration. Ultrasonic pachometer measurement of the variation in corneal thickness (3-168 h) showed a dose-dependent response (p<0.01) from the 8th to the 168th hour. Uveitis and considerable increases in the levels of the prostaglandin E2 (4.50+/-0.40 pg/0.1 ml vs. 260.03+/-2.03 pg/0.1 ml), total protein (0.25+/-0.05 g/l vs. 2.10+/-0.08 g/l), albumin, albumin/globulin and leukocytes were observed in the aqueous humor 24 h after topical application of croton oil 3% (40 microl). All the values obtained were statistically significant (p<0.01).
Conclusions: The topical application of 3% croton oil (40 microl) was most appropriate for the evaluation of the inflammatory process in the anterior chamber and for the determination of the effects of intraocular penetration. The inflammatory mechanism in this model is thought to involve the activation of the arachidonic acid pathway accompanied by the breakdown of the blood-aqueous barrier permitting high molecular weight proteins to enter the aqueous humor. Typology: anterior uveitis with corneal edema.