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.

[Systematic search of the posterior vitreous cortex during vitrectomy. Technique, complications and results]. / Recherche systématique du cortex vitréen postérieur lors de la vitrectomie. Technique, complications et résultats.

We present the results of a prospective study trying to answer the question: when a clinical or echographic premacular vitreous detachment occurs, is it still possible to find a preretinal membrane at the surface of retina? We looked for such a membrane in 50 consecutive vitrectomies for various indications. We found and removed such a membrane in 42 cases but were unable to obtain histological examinations. Our conclusions are: most of the time, the diagnosis of total vitreous detachment is very difficult and the finding of a premacular membrane during vitrectomy is a frequent event.

Simulation of the growth pattern of the central retinal artery using a fractal modeling technique.

Assisted by computer, we simulated the typical growth pattern of the central retinal artery by a fractal modeling technique. When processing was started with two fertile sides, an iterative processing function generated a ramiform fractal. The branching angle was chosen at random within a certain range. In addition, a feedback restriction forbade any intersection of branches. We demonstrated that the curved shape of the temporal vessels is caused by simultaneous growth of the vessels and the retina. When processing was begun with only one fertile side, the typical vascular pattern of a retinal coloboma was designed.

[Retrospective study of complications of 329 YAG laser capsulotomies]. / Retrospektive Studie über die Komplikationen von 329 YAG-Laserkapsulotomien.

In 329 cases that had undergone YAG laser posterior capsulotomy after uncomplicated cataract surgery with implantation of a posterior chamber intraocular lens, 32.8% developed both early and late complications. In 19.8% we found an increase in intraocular pressure (IOP), and 95.4% of the cases appeared within 1 month after the capsulotomy. One case of increased IOP needed surgical treatment for glaucoma after unsuccessful conservative therapy. Macular edema developed in 7.9% of the cases and retinal detachment in 3%. Two characteristics of retinal detachment were an axial length of more than 26 mm and the development of vitreoretinal proliferation.