| Complications of the proliferative diabetic retinopathy are vitreous hemorrhage that does not resolve, traction on the retina caused by fibrovascular proliferation that detaches or treatens the macula . Pars plana vitrectomy is the popular way to treat these complications . but it is so difficult and dangerous to remove the proliferative membrane from the retina very clearly with mechanical means. Because the adhesion between the proliferative membrane and the retina is various and particularly strong in PDR . These means usually lead to a lot of complications including retinal hemorrhage , damage to the nerve fiberlayer, vitreous hemorrhage or even retinal breaks . Pharmacologic vitreolysis refers to intravitreal injection of some enzymes that digest and detach the proliferative membrane from the retina and that lead to vitreous liquefaction to assist or replace the standard mechanical vitrectomy . According to the pathoanatomical change in PDR and the defection of the standard mechanical vitrectomy, we proposed to demonstratethe feasibility of t-PA assisted vitrectomy for PDR in order to find a way to facilitate vitrectomy and to decrease complications of the standard mechanical vitrectomy of the PDR , basing on the previous experimental study of us .Purpose: To assess the efficacy of t-PA in digesting and detaching the proliferative membrane from the retina in PDR . To determine whether complications of the standard mechanical vitrectomy for PDR could be decreased . To investigate the retinal toxicity of intravitreal commercial recombinant t-PA solution through clinical study .Methods: Fifty-four patients(55eyes) receiving surgery for complications of PDR were divided into two groups . In this prospective, randomized, doubled-blind, two stages study, Group I 29 patients (30eyes) received 100ug/0.2ml of intravitreal t-PA in buffered salt solution(BSS) three days before vitrectomy , agents were injected into the clearance between the proliferative membrane and retina though insight and direction of the fiberoptic . After injection , the patient was asked to keep in demanding position in order to get enough touch between agents and the proliferative membrane . GroupII 25 patients(25eyes) received only BSS. The means of injection and the position patients keeped were same of Group I. All experiemental eyes were examined by slit-lamp biomicroscopy, binocular indrect ophthalmiscopy, 90D double aspheric preset lens,B-scan and eletroretinography. Postoperative follow-up lasted up to 6 months. The major criteria for comparison werethe number of intraoperative iatrogenic tears, the percent of unstuck dots and the variation of ERG B-wave amplitude before and after the intravitreal injection, the gain in visual acuity and the reattachment rate of traction retinal detachments.Results: There were 5 eyes achieved complete posterior vitreous detachment and vitreous hemorrhage was mostly absorbed in Group I; but there was no eye achieved complete posterior vitreous detachment in Group II. The percentage of unstuck dots between the proliferative membrane and retina in Group I was 63.7%; Group II was 26.4%. 3 eyes in Group I occurred iaterogenic tears, the rate of iaterogenic tears was 10%; 9 eyes in GroupII was found to have iaterogenic tears, the rate of iaterogenic tears was 36%. In Group I , all patients had an acuity that was more than the preoperative level; In Group II, 20 eyes had an acuity that was more than the preoperative level, 4 eyes had an acuity that was unchanged, one eye had an acuity that was less than the preoperative level. The average preoperative visual acuity was 2.81±0.92 and postoperative was 4.17±0.72, the mean gain of visual acuity was 1.3(logMAR) in Group I ; The mean preoperative acuity was 2.64±0.68 and postoperative was 3.56±0.77, the mean gain in visual acuity was 0.92(logMAR) in GroupII. At 6 months, In Group I the reattachment rate of traction retinal detachment was 100%; In GroupII there were 20 eyes that were reattached, 4 eyes were reattached after the second operation, one eye was not reattached. Before intravitreal injection , the average ERG...
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