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

To evaluate an animal model used to study intraocular pressure (IOP) development after aqueous exchange with several commercially available ophthalmic viscosurgical devices (OVDs).

Department of Preclinical Ophthalmology, Pharmacia & Upjohn, Uppsala, Sweden.

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).

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.

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.