Biodegradable tube implants in experimental glaucoma surgery in the rabbit

Although ocular drainage implants are manufactured from biocombatible materials to reduce foreign-body reaction, the formation of excessive scar tissue around the implant is a common cause for implant failure. In this study, the suitability of poly(D, L-lactide-co-glycolide) copolymer, impregnated with an antiproliferative agent retinoic acid, was evaluated as a material for biodegradable tubular implants, as well as the duration and magnitude of the intraocular pressure reduction obtained with the prototype implant. Subconjunctivally placed retinoid-impregnated polymer particles caused a milder inflammatory reaction than plain polymer, and the layer of connective tissue around the material was thinner after the follow-up period of 60 d. In the anterior chamber, the inflammatory response elicited by the material was milder than subconjunctivally. The plain polymer caused a transiently stronger reaction than the retinoid-impregnated polymer, but after 60 d no difference was evident between the two materials. In all operated eyes with the tubular implant, the intraocular pressure was statistically significantly lower (p<0.05) than in control eyes for 9 wk after the operation. The intraocular pressure of the eyes with the retinoid-impregnated implant was statistically significantly lower (p<0.05) than in eyes with a plain polymer implant for up to 7 wk post-operatively. However, the use of retinoid did not prolong the effective functioning time of the implants.