Biomedical subjects

G W Abrams

Publications and source records attributed to G W Abrams.

9 recordsLinked to original sources

PubMed1992

Macular phototoxicity caused by fiberoptic endoillumination during pars plana vitrectomy.

Three cases of retinal phototoxicity were caused by light from the endoilluminator used in vitrectomy. Preoperative clinical examination, color photography, and fluorescein angiography in all three cases failed to disclose retinal pigment epithelial changes. Postoperative clinical findings, photographs, and fluorescein angiograms are highly suggestive of the presence of retinal phototoxicity. The characteristics of these lesions and surgical conditions implicate the endoilluminator as the source of photic injury. The macular lesions were noted within one week of the surgical procedure, measured between 2 and 5 disk diameters in size, involved the fovea in two eyes, and resulted in marked decrease in visual acuity in two of three eyes, with persistence in one eye. Initially, whitening of the outer retina was present, but was replaced by pigmentary mottling at the level of the retinal pigment epithelium within a few weeks. Preventive measures to avoid macular phototoxicity associated with vitrectomy are discussed.

Adult↗

PubMed1992

Combined phacoemulsification, pars plana vitrectomy, and posterior chamber intraocular lens insertion.

Eighteen eyes with coexisting cataract and vitreoretinal disease underwent combined phacoemulsification, pars plana vitrectomy, and posterior chamber lens implantation. Preoperative vitreoretinal disease included nonclearing vitreous hemorrhage (eight eyes), vitreous hemorrhage and tractional retinal detachment (three eyes), tractional retinal detachment (one eye), epiretinal membranes (three eyes), peripheral uveitis (two eyes), and a retained intraocular metallic foreign body (one eye). Postoperative visual acuity improved in each case; 14 eyes achieved visual acuity between 20/20 and 20/80 during an average postoperative period of 11 months (range, 3 to 39 months). Perioperative complications included an iatrogenic retinal break (one eye) and pupillary block glaucoma (one eye). Four eyes required YAG laser capsulotomy postoperatively. Phacoemulsification did not interfere with corneal clarity, allowed water-tight wound closure during vitrectomy, and preserved the capsular bag, allowing endocapsular fixation of the posterior chamber lens. Combining phacoemulsification, posterior chamber lens implantation, and pars plana vitrectomy allows rapid visual rehabilitation and functional unaided vision in these eyes.

Adult↗

PubMed1992

Vitrectomy for diabetic macular traction and edema associated with posterior hyaloidal traction.

Pars plana vitrectomy with separation of the posterior hyaloid was performed in 10 eyes with diabetic macular edema and traction associated with a thickened and taut premacular posterior hyaloid. Nine of the 10 eyes had previous macular photocoagulation. Preoperative fluorescein angiography showed a deep and diffuse pattern of leakage in the macula. Intraoperatively, the attached and thickened posterior hyaloid was lifted and separated from the retina. Postoperatively, vision improved in nine eyes. The macular traction and edema resolved in eight eyes and decreased in two. Complications included a vitreous hemorrhage, a rhegmatogenous retinal detachment, cataract formation, and a mild epimacular membrane, each occurring in one eye. Vitreous surgery can improve the visual prognosis of some eyes with diabetic macular traction and edema associated with a thickened and taut posterior hyaloid.

Adult↗

PubMed1992

The lowest effective dose of tissue plasminogen activator for fibrinolysis of postvitrectomy fibrin.

Tissue plasminogen activator (tPA) has been shown to be effective at a dose of 25 micrograms in the treatment of severe postvitrectomy fibrin. However, a recent report based on an animal model indicates that retinal toxicity may occur at doses as low as 25 micrograms. This study uses a low dose (1.5 micrograms to 3 micrograms) of tPA for 34 injections in 26 eyes, and determines the lowest effective dose to be between 1.5 and 3 micrograms. Complete fibrinolysis was achieved in all 28 eyes in which 3 micrograms of tPA was administered within 10 days of vitrectomy, whereas partial fibrinolysis was achieved in eyes treated with 3 micrograms of tPA 27 days and 82 days after vitrectomy. Complete fibrinolysis occurred in only 1 of 4 eyes that receive 1.5 micrograms of tPA. A dose of 3 micrograms of tPA is recommended for treatment of severe fibrin after vitrectomy, as it has a wider margin of safety than do higher doses.

Adolescent↗

PubMed1991

A technique for facilitated visualization and dissection of the vitreous base, pars plana, and pars plicata.

We describe a technique to facilitate visualization of the vitreous base, pars plana, and pars plicata during vitreous surgery. This technique takes advantage of an externally applied fiberoptic light source coupled with scleral depression to enable direct viewing of the ciliary processes and anterior vitreous base. No special instrumentation or alteration in pars plana vitrectomy techniques is required. We have used this technique to enhance anterior dissection during vitrectomy surgery in the aphakic and pseudophakic eye associated with proliferative vitreoretinopathy, diabetic retinopathy, epithelial down-growth syndromes, and postvitrectomy fibrin formation.

Eye Diseases↗

PubMed1979

Experimental double-perforating injury of the posterior segment in rabbit eyes: the natural history of intraocular proliferation.

A reproducible model of double perforating injury of the posterior segment of the rabbit eye was developed. Immediately after injury, a viterous condensation was visible between wounds. The scleral exit wound was sealed by fibroblastic proliferation of probable episcleral origin by the fourth day and the entrance similarly by the seventh day. Cellular proliferations originating in the wounds crossed the vitreous cavity following the vitreous injury tract or condensed vitreous to the disc or to the vitreous base. The earliest intraocular proliferations, composed of spindle-shaped, fibroblast-like cells, were seen at day 4. Occasional pigment epithelia were present in and on these proliferations. Other proliferations occurred directly on the retinal surface adjacent to the wounds. The transvitreous proliferations employed the vitreous as a scaffold, while the surface proliferations used the retinal surface for contact guidance.

Animals↗

PubMed1979

Vitrectomy for injury: the effect on intraocular proliferation following perforation of the posterior segment of the rabbit eye.

Perforating injuries were produced in the posterior segments of rabbit eyes. A control group had no surgery; a second group underwent closed vitrectomy immediately after injury; and a third group had closed vitrectomy delayed two weeks following injury. The eyes were then observed for four weeks. Transvitreal proliferation, which was found in each of the control eyes, was effectively prevented in the eyes that underwent immediate vitrectomy. Established transvitreal proliferation was removed and its recurrence prevented by delayed vitrectomy. These results establish the principle that vitreous acts as a scaffold for proliferation. Removal of the vitreous eliminates the structures along which proliferation can occur and thus effectively prevents transvitreal proliferation. Early removal of vitreous in severely injured eyes with vitreous damage is recommended.

Animals↗

PubMed1978

An improved method for practice vitrectomy.

Practice is essential for acquiring the skills necessary for the delicate technique of pars plana vitrectomy. An improved animal model is presented for the beginning surgeon and the assistant to learn basic as well as advanced vitrectomy techniques. A stepwise scheme progressing from simple vitrectomy in the phakic rabbit eye to complicated situations is introduced. Fluorescein staining helps in visualization of the normal vitreous. Double perforating injuries are created to simulate complicated vitreoretinal problems. Methods for learning manipulations with two instruments in the eye are described.

Animals↗

PubMedDate not supplied

Collagen shield delivery of tissue plasminogen activator: functional and pharmacokinetic studies of anterior segment delivery.

BACKGROUND: Postoperative fibrin formation remains a major complication associated with intraocular surgery, especially after vitreoretinal surgery for proliferative vitreoretinopathy, proliferative diabetic retinopathy, trauma, or endophthalmitis. Tissue plasminogen activator (tPA) has been shown, both in experimental studies and clinical trials, to specifically dissolve formed intraocular fibrin after intracameral or intravitreal injection. We studied collagen shield delivery of tPA to the anterior segment and vitreous of rabbit eyes to evaluate a noninvasive delivery modality. METHODS: Anterior segment fibrin clots were formed in rabbit eyes by injecting citrated rabbit plasma. The tPA hydrated collagen shields, or control shields, were then placed on the rabbit corneas and the extent of fibrin clot was followed. In other rabbit eyes, tPA hydrated collagen shields were placed on the rabbit corneas and an enzyme-linked immunosorbent assay (ELISA) was utilized to determine aqueous, vitreous, and blood levels of tPA over time. RESULTS: Collagen shield tPA delivery shortened the time to fibrin clot lysis by 50% (mean clearance time = 49 +/- 23 hours; P less than .05). ELISA for tPA levels noted measurable vitreous levels by 2 hours after tPA hydrated collagen shield application with a peak at 24 hours. Aqueous tPA levels were not measurable until 18 hours after tPA collagen shield application and peaked at 36 hours. Vitreous tPA levels were greater than aqueous tPA levels at all time points (P less than .05). No evidence of corneal edema or opacification, hemorrhage, or cataract was seen. CONCLUSIONS: These results document the efficacy and safety of tPA delivery to the aqueous and vitreous via a hydrated collagen shield in this animal model.

Absorption↗