All the experiments were performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Two sets of experiments were conducted: one with rigid polyethylene devices and the second with flexible silicone devices.
In the first set of experiments, New Zealand White rabbits (8–10 lb.) were anesthetized and had a rigid polyethylene device
(Fig. 1A)sutured to the sclera of one eye to provide apposition (apposition group,
n = 4) or sutured tightly causing the rim of the device to indent the sclera (indentation group,
n = 4). Once the devices were in place, the sclera formed one wall of the compartment and was the only surface through which diffusion could take place. Nine milligrams of fluorescein sodium (Sigma-Aldrich, St. Louis, MO) was compressed into pellets by a manual press system (International Crystal Laboratories, Garfield, NJ) with 10 ft
2 of torque applied to a die set of 4 mm. Fluorescein pellets were placed in each of the exoplants. A third group of rabbits (
n = 3) received a periocular injection of 9 mg of fluorescein in 0.09 mL of phosphate-buffered saline (PBS). At baseline and at several time points after implantation or injection (0.25, 1, 3, 12, 24, and 48 hours, 5 and 7 days), ocular and plasma fluorescein levels were measured with an ocular fluorophotometer (FM-2 Fluorotron Master; Occumetrics, Mountain View, CA). Measurements were performed at least twice, and two consistent measurements were averaged to provide one data point for analysis.
In the second set of experiments, New Zealand White rabbits (8–10 lb) were anesthetized, and a flexible refillable silicone device
(Fig. 1B)was sutured to the sclera. Fluorescein was diluted at 10% in a water-soluble viscous vehicle (Bion Tears; Alcon, Fort Worth, TX) composed of dextran (0.1%) and hypromellose (0.3%). A volume of 0.05 mL (5 mg) of this solution was injected into the periocular space in close apposition to the sclera (
n = 3) or into the empty reservoir of the preplaced silicone device (
n = 4) while venting with another needle. Ocular and plasma fluorophotometry were performed at baseline and at 1, 3, 6, 24, and 48 hours and 5, 7, 14, 28, and 52 days after the procedure.
External ocular examinations and indirect ophthalmoscopy were performed during the first 2 weeks and before euthanasia, 2 months after implantation. Eyes, including the attached exoplant and overlying conjunctiva, were rapidly removed and frozen in optical cutting temperature embedding solution (Miles Diagnostics, Elkhart, IN). Ocular sections (10 μm) were stained with hematoxylin and eosin and examined by light microscopy.