Intraocular pressure development in the rabbit eye after aqueous exchange with ophthalmic viscosurgical devices.

PURPOSE: To evaluate an animal model used to study intraocular pressure (IOP) development after aqueous exchange with several commercially available ophthalmic viscosurgical devices (OVDs). SETTING: Department of Preclinical Ophthalmology, Pharmacia & Upjohn, Uppsala, Sweden. METHODS: Albino rabbits (New Zealand White) were used. Aqueous humor (50 microL) was exchanged with 8 OVDs. The IOP was measured every second hour for 12 hours and then 24, 48, and 72 hours after aqueous exchange using a pneumotonometer (Modular One, Bio-Rad Digilab Inc). A minimum of 7 eyes was used for each OVD. Healon was used as control in 1 eye in all experiments. The OVDs were Viscoat (chondroitin sulfate-sodium hyaluronate), Provisc (sodium hyaluronate), Biolon (sodium hyaluronate), Healon GV, Healon5, Ophthalin (sodium hyaluronate), Ocucoat (hydroxypropyl methylcellulose), and Ivisc (sodium hyaluronate). RESULTS: All OVDs caused a postoperative increase in IOP. At 24 hours, the IOP was at the preoperative levels. However, there was considerable variation in the maximum IOP value and when this value occurred. The maximum value appeared to depend on the concentration of the rheologically active substance in the product and the time of the average molecular mass. There was also an increase in central corneal thickness, with a maximum increase 24 hours after the exchange but a large variation among animals. CONCLUSION: The animal model appears to be useful for comparing various OVDs, and the results may serve as a guide for the design of clinical studies of new products.

Effect of diclofenac on prostaglandin liberation in the rabbit after photorefractive keratectomy.

BACKGROUND: An analyses of the concentration of arachidonic acid metabolites and the infiltration of leukocytes in the aqueous humour of rabbits after excimer laser keratectomy was performed. The ability of topical diclofenac to block prostaglandin E2 liberation into the aqueous humour was also investigated. METHODS: Photorefractive keratectomy was performed on both eyes of 60 New Zealand rabbits. Prostaglandin E2, 6-keto prostaglandin F1 alpha and thromboxane B2 were detected by radioimmunoassay and leukocytes were counted in the aqueous humour for 120 hours postoperatively. Topical diclofenac was instilled (1 drop/4h) in six animals and prostaglandin E2 was analyzed in the aqueous humour 16 hours postoperatively. RESULTS: The prostaglandin E2 concentration in the aqueous humour increased from 13 in control animals, to 251 pg/100 microliters at 16 hours after treatment (p < 0.05). A statistically significant elevation in the aqueous concentration of 6-keto prostaglandin F1 alpha could not be demonstrated. Thromboxane B2 and leukocytes could not be detected at any time point. Topical diclofenac (1 drop/4h) reduced the levels of prostaglandin E2 in the aqueous humour below 10 pg/100 microliters, 16 hours postoperatively. CONCLUSION: Topical diclofenac (1 drop/4h) inhibited prostaglandin E2 release into the aqueous humour.

Inflammatory response in the rabbit after phacoemulsification and intraocular lens implantation using a 5.2 or 11.0 mm incision.

PURPOSE: To study the effect of two incision sizes, 5.2 and 11.0 mm, on the inflammatory response in rabbit eyes after lens extraction with phacoemulsification. SETTING: S:t Erik's Eye Hospital, Stockholm, and Pharmacia, Uppsala, Sweden. METHODS: Bilateral endocapsular phacoemulsification was performed on 32 rabbits. The wound was enlarged to 5.2 mm, and a poly(methyl methacrylate) intraocular lens (IOL) was implanted in the capsular bag. In each rabbit, one eye was selected at random and the wound in that eye enlarged to 11.0 mm. In both eyes the wound was sutured with a 9-0 polypropylene continuous suture. The number of white blood cells (WBCs) and prostaglandin E2 (PGE2) in the aqueous humor were measured at days 1, 3, 7, and 28 postoperatively. Corneal thickness was also measured by pachymetry. RESULTS: The number of WBCs at day 3 and the PGE2 levels at days 1, 3, and 7 were significantly higher in eyes with 11.0 mm incisions than in eyes with 5.2 mm incisions. One week after surgery, the corneas in the eyes with 11.0 mm incisions were significantly thicker than in those with 5.2 mm incisions. CONCLUSION: The results indicate that incision size is an important factor in the inflammatory response following phacoemulsification and IOL implantation in the rabbit eye.

PGE(2) and leucocyte levels in aqueous humor after lens extraction and intraocular lens implantation.

In order to study the inflammatory response after cataract surgery and intraocular lens implantation the leukocyte (WBC) and prostaglandin E(2) (PGE(2)) levels in aqueous humor were measured in rabbit eyes at different time points (1, 3, 7, 14 and 28 days) postoperatively. In the first group lenses were implanted in the anterior chamber of the eye, without lens extraction, while in the second group the lens was removed and the IOL was placed in the capsular bag. A third group of animals was injected with 10 ng endotoxin into the vitreous in order to induce an inflammation of the uvea. In the endotoxin group high levels of WBC and PGE(2) were observed at 24 h postoperatively, followed by a decrease over time. In the intraocular lens groups WBC and PGE(2) were detected at all time points, and at higher levels compared to the endotoxin group. The WBC was high at day 1 and 3, declined over time, and then increased at day 28 postoperatively. The PGE(2) level was highest at day 3 in rabbits with anterior chamber lenses, while it peaked at day 7 in the animals with IOLs implanted in the capsular bag. In animals with the extracapsular lens extraction without an implanted IOL, the levels of WBC and PGE(2) decreased over time, and were statistically lower after one week compared with animals with an IOL placed in the capsular bag. The results demonstrate that the inflammatory response after cataract surgery persists for at least one month, probably due to surgical trauma and foreign body reactions. PGE(2) and WBC could be used to study postoperative trauma and biocompatibility of different IOL materials and designs.

Aqueous humor polyamines and alkaline phosphatase activity in endotoxin-induced uveitis: correlations to diverse leukocyte subsets.

The polyamines putrescine, spermidine and spermine have been proposed to be a part of the acute phase inflammatory response. They have been shown to be useful markers for cellular kinetics and change with various pathological conditions. The hypothesis that aqueous humor polyamines could be used to follow the time course of an endotoxin-induced inflammation in the eye was investigated. Additional parameters studied were the amount of aqueous leukocytes, alkaline phosphatase activity, distribution of leukocyte subsets and breakdown of the blood-aqueous barrier. Aqueous leukocytes, protein, alkaline phosphatase activity, putrescine and acetylated spermidine increased significantly as a response to inflammation during the first days after uveitis induction. Spermidine decreased 24 h after injection and seemed to rise thereafter. The different polyamines, except spermidine, correlated to the diverse infiltrating leukocyte subsets. These observations indicate that aqueous polyamines may be applied as valid markers for inflammation in the eye.