Prevention of experimental proliferative vitreoretinopathy with a biodegradable intravitreal implant for the sustained release of fluorouracil.

OBJECTIVE: To test the efficacy of a biodegradable device for the intravitreal sustained release of fluorouracil in the treatment of tractional retinal detachment due to proliferative vitreoretinopathy. METHODS: A 6 x 0.9-mm (20-gauge) cylindrical solid implant molded from copolymers of lactide and glycolide admixed with 1 mg of fluorouracil was placed in the vitreous cavity of rabbits in which retinal detachment with proliferative vitreoretinopathy had been initiated. Comparisons of the control (drug-free polymer) and experimental (fluorouracil polymer) groups were made with weekly indirect ophthalmoscopic examinations. In another experiment, the intravitreal concentration of fluorouracil was tested at each time point. RESULTS: Retinas of eight (89%) of nine rabbits that received the polymer with fluorouracil remained attached compared with only one animal (11%) that received the control polymer without the drug. The therapeutic effect of the drug-containing implant was associated with sustained intravitreal concentrations of fluorouracil between 1 and 13 mg/L for at least 14 days, and fluorouracil concentrations remained above 0.3 microgram/mL for almost 21 days. No evidence of the toxic effects of the drug or polymer implant was observed with electroretinographic and histopathologic study. CONCLUSION: Intravitreal implantation of biodegradable polymers containing fluorouracil can prevent proliferation of epiretinal membranes resulting in complicated retinal detachment in an animal model of proliferative vitreoretinopathy and indicate their possible usefulness for intravitreal delivery of therapeutic agents.

Hypodermic stainless steel tacks and companion inserter designed for peripheral fixation of retina.

Mechanical fixation of the torn or cut edge of retina with 30-gauge hypodermic stainless steel tacks has been performed in 15 patients at the Bascom Palmer Eye Institute, Miami, and Miami Veterans Administration Medical Center with six to 18 months of follow-up. The companion tack inserter allows the surgeon to select an angle for the shaft of the tack in relation to the inserter to allow the tack to be driven perpendicularly into sclera even when the insertion is anterior to the equator. If residual detachment remains following fluid-gas exchange after preliminary placement of the retinal tacks, a given tack may be removed and reinserted to facilitate complete retinal reattachment. This utilitarian feature allows the surgeon to eliminate residual anteroposterior traction following complete membrane peeling by extending relaxing retinotomies and tacking the posterior cut edge of the retina securely between the ora serrata and the equator.

Comparison of low- and high-volume irrigation-aspiration systems for extracapsular cataract extraction.

A low-volume irrigation-aspiration system with a 1-mm tip (0.3-mm aspiration port) has been developed for extracapsular cataract extraction. This autoclavable system uses approximately 36% less irrigating fluid during the irrigation and aspiration of cortical material when compared to currently available models. The time required for cortical aspiration is also shortened by 33%. After three years of clinical experience with the low-volume system at the Miami Veterans Administration Medical Center, where almost all extracapsular cataract surgery is now performed with the new system, there have been no adverse effects and subsequent capsulotomy has rarely been necessary.

Prostaglandin levels in human vitreous.

Vitreous samples were obtained from 41 eyes undergoing vitrectomy, and radioimmunoassays were performed to measure concentrations of the prostaglandins PGE2, PGF2 alpha, prostacyclin, and thromboxane. Presumably physiological levels (approximately 100 picograms/ml) were found in vitreous from eyes undergoing cataract extraction. Eyes with vitreous haemorrhage, retinal detachment, or cystoid macular oedema had similarly low levels. Vitreous prostaglandins were mildly elevated in trauma and endophthalmitis and markedly elevated in aphakic bullous keratopathy. The role prostaglandins may play in cystoid macular oedema is reviewed.

Intraocular diathermy coagulation.

Previously used transvitreal diathermy systems were found to be less than adequate. A new, safer 1.25 MHz medium frequency bipolar instrument is presented, which obviates most of the earlier drawbacks. Coagulation at the retinal surface can be obtained with as little as 0.15 J.

A bipolar coaxial microprobe for safe transvitreal diathermy.

We present a new 22-gauge transvitreal bipolar diathermy microprobe. With the use of the coaxial principle, the current flows only at the probe's end surfaces. Because of its small size and end-on coagulation effect, and when used in conjunction with a low-frequency diathermy unit, the probe can be used safely on vessels lying directly on the retinal surface and close to the optic nerve head. We report three cases to demonstrate the usefulness of this instrument.

Retrolental fibroplasia: I. Clinical observations.

The changes occurring in retrolental fibroplasia were studied in 97 premature infants with fundus photography and fluorescein angiography. The macrovascular lesion of proliferative retrolental fibroplasia was identified as a functioning arteriovenous shunt. The microvascular abnormalities were capillary tufts, collaterals, capillary-free zones, and neovascular membranes. Regression was signaled by the ingrowth of capillaries from the shunt into the avascular retina. Cicatrization was characterized by persistence of the vascular abnormalities of the proliferative phase and organization of the avascular retina into a contracting scar.

Vitreous surgery and retinal detachment.

Vitrectomy has proved to be extremely useful in facilitating reattachment of the retina in a variety of complicated detachments. The author's experience has been exclusively with the vitreous infusion suction cutter. Several other, similar, instruments are now available, and they are described in a recent review article on vitreous surgery [8]. The techniques required for successful surgery are not easily mastered, and it is the author's practice to have a trainee assist on about 50 operations before assuming major responsibility for a difficult microdissection.