Clinical Study On Posterior Vitreous Detachment Induced By Recombinant Human Tissue-type Plasminogen Activator During The Vitrectomy

The status of the vitreoretinal border region is related to many fundus diseases.Proliferative vitreoretinopathy is the main cause of failure to rhegmatogenous retinal detachment surgery, and also the result of serious traumatic,vascular and inflammatory retinopathy.The foundation of pathoanatomical changes in proliferative vitreoretinopathy( PVR) is the proliferative membrane, of which the vitreoretinal junction play a key role in the formation. Posterior vitreous detachment(PVD) is a separation of the cortical vitreous gel from the inner limiting lamina as far as the posterior border of the vitreous base.It is a age-related pathological process.But found clinically,complete PVD has an impact on the course of various vitreoretinal disorders including diabetic retinopathy,macular hole,retinal vein occusion and so on.And complete removal of the cortical hyaloid is often a primary aim of vitreretinal surgery. Vitrectomy is the popular way to treat PVR now. but it is so difficult and dangerous to remove theproliferative 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 agents that alter the molecular organization of vitreous to achieve posterior vitreous detachment and detach the proliferative membrane from the retina and that lead to vitreous liquefaction to assist or replace the standard mechanical vitrectomy。A number of enzymes have been used experimentally to modify vitrous structure and/or to induce PVD . Recombinant human tissue-type plasminogen activator (RT-PA) is one of them.RT-PA is a serine protease that mediates the fibrinolytic process and modulates the extracellular matrix.It hydrolyze a variety of glycoproteins , including laminin and fibronecin,bothof which are present at the vitreoretinal interface and are thought to play a key role in vitreoretinal attachment., RT-PA holds theoretical promise to induce PVD without damaging the ILM and the retina .To assess the efficacy of RT-PA to achieve posterior vitreous detachment.To determine whether complications of the standard mechanical vitrectomy for PDR could be decreased .To investigate theretinal toxicity of intravitreal commercial recombinant t-PAsolution through clinical study.The study included 20 eyes from 20 patients underwent PPV. Anterior core vitrectomy was performed , 0.1 mL of RT-RA solution was injected into the midvitreous cavity or into the clearance between the posterior hyaloid and retina surface though insight and direction of the fiberoptic for about 10-15 minutes. After injection,the patient was asked to keep in demanding position in order to get enough touch between agents and the proliferative membrane. All eyes were examined by slit-lamp biomicroscopy, binocular indirect ophthalmiscopy, double aspheric presetlens,B-scan andelectroretinography. Postoperative follow-up lasted up to 2-4 months. The major criteria for comparison were the number of intraoperative iatrogenic tears, 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.There were 17 eyes achieved complete posterior vitreous detachment, the rate was 85% , there were 3 eyes achieved partial posterior vitreous detachment ,the rate was15%. 1 eye occurred iatrogenic tear, the rate of iatrogenic tear was 5%; Before intravitreal injection , the average ERG B-wave amplitude was 260.28uv; after injection, the average ERG B-wave amplitude was 261.17uv. There were no variation between before and after injection.Postoperative follow-up lasted up to 2-4 months,there were 17 eyes had an acuity that was more than the preoperative level;3 eyes had an acuity that was as the same as preoperative level, there were 17 eyes that were reattached, 1 eyes was reattached after the second operation, two eyes were not reattachedbecause it is so difficult and dangerous to remove the proliferative membrane from the retina very clearly and can't see detachment of retina lasted up to 4 months. In conclusion, RT-PA achieved posterior vitreous detachment in the Vitrectomy ,the gain in visual acuity, the reattachment rate of traction retinal detachments were higher than reports, the rate of iatrogenic tears was less than the other reports .Furthermore, there were no complications occurred with the use of RT-PA.It has been knowed that posterior detachment of vitreous(PVD) is closely correlated to the development and prognosis of many vitreous-retinal diseases, just as rhegmatogenous retinal detachment, macular hole, branch retinal vein occulsion(BRVO), et al. The existence of complete PVD can ameliorate the prognosis of these diseases. The existence of PVD induced by drug can decrease the difficute of Vitrectomy and diminution the opportunit of complications.Furthermore, it is important to prevente proliferative vitreoretinopathy (PVR) after Vitrectomyand facilitate the recovery of vision. A drug-Vitrectomy with clinical application prospect is expected to be found. Currently,recombinant human tissue-type plasminogen activator , RT-PA assisted vitrectomy in the Traumatic Pediatric Macular Holes, Stage 3 macular holes, proliferative diabetic retinopathy, diabetic macular edema.The result indicate that RT-PA helps separate the vitreous hyaloid from the ILM surface .This result give us confidence to study furtherly.Clinical use of plasmin inducing PVD has extensive prospects.If plasmin can be safely used in clinic,not only can it solve the difficulty of vitrectomy ,but also can treat or preserve some vitroretical diseases,even become a adjunct to other traditional methods.