Tissue plasminogen activator as a biochemical adjuvant in vitrectomy for proliferative diabetic vitreoretinopathy

Tissue plasminogen activator (TPA) converts plasminogen to plasmin, thereby inducing fibrinolysis. In ophthalmologic surgery of subretinal hemorrhages, it is used to dissolve blood clots. As the blood-retina barrier of diabetic patients has broken down, plasminogen can enter the vitreous compartment in these cases. It is known that plasmin dissolves extracellular matrix protein in the vitreous interface. For that reason se used TPA in pars plana vitrectomy (ppV) of proliferative diabetic vitreous retinopathy (PDVR). Ten patients undergoing ppV for PDVR of stage A or B (Kroll classification) were included in a prospective study. At 15 min prior to vitrectomy, 100 microliters balanced salt solution was injected into the vitreous cavity. As randomized, the injection fluid contained either 25 micrograms TPA or only buffer solution. At this stage, the operating surgeon did not know whether TPA was injected or not. The grade of difficulty and complications of the operation were scored and documented. In all cases the operating surgeon correctly classified verum or placebo after surgery. Preparation of vitreous cortex and pathological membranes proved to be less difficult when TPA had been injected. Moreover, no severe bleeding occurred in this group in spite of marked PDVR. We conclude that TPA can be used in ppV without producing severe side effects. Disintegration of the vitreous interface causes a posterior detachment of the vitreous body, thus facilitating ppV.