Enzyme-assisted vitrectomy in enucleated pig eyes: a comparison of hyaluronidase, chondroitinase, and plasmin

Purpose. Facilitation of vitrectomy by vitreolytic enzymes may be of great value in complicated or office-procedure vitreo-retinal surgery. In this study, we quantified and compared the effect of hyaluronidase, chondroitinase, and plasmin pre-incubation on vitrectomy rate and explored potential retinal damage. Methods. Freshly enucleated pigs eyes were incubated (1 or 3 hours) with an intravitreally injected enzyme or control solution. Enzyme doses were 100 and 1000U for hyaluronidase, 1 and 2U for chondroitinase, 3 and 30U for plasmin. The eyes were weighed before and after 10 minutes of one-port vitrectomy, the difference representing the amount of removed vitreous. Light microscopy was used to assess potential damage to the retina. Results. All enzymes significantly increased the amount of removed vitreous at all doses and incubation periods. The highest increase was found with hyaluronidase 1000U 3 hours, the lowest with chondroitinase 1 U, 1 hour. Damage occasionally occurred to the internal limiting membrane and very rarely to the nerve fiber layer. No damage at all was seen in the 100 and 1000U hyaluronidase (1-hour incubation) groups. Conclusions. Hyaluronidase, chondroitinase, and plasmin are good candidates for enzyme-assisted vitrectomy. Although retinal structural damage was very rarely seen, safety concerns will have to be investigated further.