Purpose: To induce a posterior vitreous detachment (PVD) in porcine and human cadaver eyes in vitro with Dispase (Gibco, Grand Island, NY).
Methods: Dispase (0.5 mL) was injected into the vitreous cavity of enucleated porcine (0.05-25 U/mL) and human (5 U/mL) eyes. After incubation 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 structural integrity of the retina was estimated by measuring the elastic constant and maximal stretching before fracture. Retinal cell viability was determined by an intracellular esterase assay. Light, transmission, and scanning electron microscopy were performed to examine the ultrastructure 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, versus 3/10 control eyes (P < 0.05). A partial or complete PVD was present in 3/5, 4/5, 5/5, or 14/15 porcine eyes after 15, 30, 60, or 120 minutes 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 demonstrated that Dispase cleaved the attachment of the posterior hyaloid to the internal limiting membrane with minimal damage to the inner retina. 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 limiting membrane with minor morphologic changes in the inner retina. The enzyme may be useful in removing cortical vitreous during vitreous surgery.