Evaluation of the "g-plant" glaucoma shunt in rabbit eyes

Purpose: To develop a miniature glaucoma shunt in order to enable a safe, quick, one-step glaucoma filtration surgery and to test the device on rabbits. Materials and methods: The shunt consists of a short (2.5 mm) 27 gauge tube to connect between the anterior chamber and the subconjunctival space after insertion through the limbus. The inner end has additional holes in its sides to overcome plugging by the iris A beveled flange prevents extrusion of the shunt and an outer oval disc prevents excessive limbal penetration and provides larger filtration area. The shunt is mounted on an introducer and is inserted into the subconjunctival space through a slit near the fornix. It is slid on the episclera towards the limbus where it penetrates the anterior chamber. A recent version of the G-plant (Optonol. Israel) was tested on one eye of 21 albino rabbits and the other eye served as control. We recorded the IOP, bleb existence and position of the implant among other parameters. Results: Each insertion lasted about 1 minute. There were no intraoperative complications. The anterior chamber flattened (25%) or became shallow immediately after the surgery but became fully formed in all animals at I day postoperatively. The side holes remained open in 95% of the animals There was transient corneal edema at the area of the shunt in 25% of the cases. Preop Day 1 Day 3 Day 7 Day 10 Day 14 lOPunop. - IOP op 0.2±24 NS -8.1±5 5 P<0 001 -5.U3.6 P<0 001 -2.2±3.7 P<0 01 -0.7±2.2 NS 0.8±2.6 NS % w. bleb 100% 90% 40% 15% 0% %extruded 5% 5% 15% 15% 15% Conclusions: Since standard filtering surgery lasts only a few days in a rabbit, the results suggest that the implanted shunt might possibly be considered as a substitute for conventional trabeculectomy. Pilot human experiments are being planned. P.