POSTERIOR VITREOUS DETACHMENT WITH DISPASE

Purpose: To induce a posterior vitreous detachment (PVD) in porcine an d human cadaver eyes in vitro with Dispase (Gibco, Grand Island, NY). Methods: Dispase (0.5 mt) was injected into the vitreous cavity of enu cleated porcine (0.05-25 U/mL) and human (5 U/mL) eyes, After incubati on at 37 degrees C for 15-120 minutes, the globes were hemisected and the extent of PVD was graded as complete, partial, or absent. The stru ctural integrity of the retina was estimated by measuring the elastic constant and maximal stretching before fracture. Retinal cell viabilit y was determined by an intracellular esterase assay. Light, transmissi on, and scanning electron microscopy were performed to examine the ult rastructure of the vitreoretinal interface. Results: After 15 minutes, a partial or total PVD was present in 7/10, 8/10, or 9/10 enucleated porcine eyes incubated with 1, 5, or 10 U/mL Dispase, respectively, ve rsus 3/10 control eyes (P < 0.05). A partial or complete PVD was prese nt in 3/5, 4/5, 5/5, or 14/15 porcine eyes after 15, 30, 60, or 120 mi nutes of treatment with 0.1 U/mL Dispase, respectively. Similarly, 19/ 20 human cadaver eyes developed a complete and 1/20 an incomplete PVD after incubation with 5 U/mL Dispase for 15 minutes. Microscopy demons trated that Dispase cleaved the attachment of the posterior hyaloid to the internal limiting membrane with minimal damage to the inner retin a. Retinal cell viability and the mechanical properties of the retina were similar for Dispase-treated and control eyes. Conclusion: Dispase disrupts the attachment of the posterior hyaloid to the inner limitin g membrane with minor morphologic changes in the inner retina. The enz yme may be useful in removing cortical vitreous during vitreous surger y.