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Biomedical subjects

R A Mittra

Publications and source records attributed to R A Mittra.

24 records · Page 2Linked to original sources
PubMed1996

Recombinant hirudin for prevention of experimental postoperative intraocular fibrin.

PURPOSE: To determine the efficacy of a specific antithrombin agent (recombinant desulphatohirudin variant 1 [Revasc, Ciba-Geigy, Ltd., Basel, Switzerland]) administered in the infusion fluid to prevent early postoperative fibrin formation in a rabbit lensectomy and vitrectomy model. METHODS: Standard fragmatome lensectomies and core vitrectomies were performed prospectively in a masked fashion on ten control eyes with lactated Ringer's infusion and on ten eyes treated with 10 microgram of recombinant hirudin/ml in the infusate. The amounts of fibrin and hemorrhage were graded in a masked fashion by using slit-lamp examination and indirect ophthalmoscopy on postoperative days 1 through 5 and on day 7. RESULTS: The difference in the mean grade of fibrin formed on the first postoperative day in the eyes treated with recombinant hirudin (mean, 0.9) in relation to the mean grade of fibrin in the control eyes (mean, 3.5) was statistically significant (P = .004). This difference was also significant on the second postoperative day (P = .01). None of the treated eyes developed intraoperative or postoperative hemorrhage. CONCLUSIONS: Recombinant desulphatohirudin variant 1 is an effective inhibitor of postoperative fibrin formation in a rabbit model and is not associated with an increased risk of intraoperative or postoperative bleeding at the tested dose. This drug may be a useful adjunct in vitreous surgery for both proliferative vitreoretinopathy and the complications of proliferative diabetic retinopathy.

Animals↗
PubMed1996

Chronic localized conjunctival chemosis.

Conjunctival chemosis is a commonly encountered clinical finding stemming from the presence of excess fluid in the conjunctiva. It is typically self-limiting or reversible if the underlying condition is treated. The authors present a series of seven cases of chronic localized conjunctival chemosis. Each patient had a localized area of dependent conjunctival edema for >or= 6 months. Evaluation of each patient included clinical examination, laboratory studies, and neuroimaging to attempt to elucidate the pathogenesis of the chemosis. Conjunctival biopsy was performed in six of the seven patients. In all of the patients studied, clinical examination uncovered no definitive signs of local inflammation. Laboratory evaluation was normal, and neuroimaging failed to confirm obstruction of venous or lymphatic drainage. Conjunctival biopsies showed chronic tissue inflammation or lymphangiectasia. The diagnosis of chronic localized conjunctival chemosis (CLCC) can be made if localized conjunctival edema persists for 6 months. Evaluation of biopsy specimens supports the theory that CLCC may result from scarring and structural alteration of conjunctival lymphatics, which appears to irreversibly affect the distribution of fluid in the conjunctiva.

Adult↗
PubMed1993

Optic nerve decompression improves hemodynamic parameters in papilledema.

PURPOSE: The purpose of this study is to examine changes in color Doppler imaging parameters before and after optic nerve sheath decompression (ONSD) for chronic papilledema caused by pseudotumor cerebri (PTC). METHODS: Color Doppler imaging was performed within 48 hours before surgery and within 48 hours after the procedure using a color Doppler unit with a 7.5-MHz phased linear transducer. Pulsed Doppler spectrum analyses were recorded digitally on videotape from the ophthalmic, central retinal, and short posterior ciliary arteries, using a 0.4 x 0.6-mm sample volume. RESULTS: Blood flow velocities in the ophthalmic, short posterior ciliary, and central retinal arteries of 24 eyes were significantly decreased compared with a healthy age-matched group. Eyes with visual acuities worse than 20/30 before surgery had significantly decreased velocities in the ophthalmic, short posterior ciliary, and retinal arteries, whereas in eyes with visual acuities better than 20/30, only the short posterior ciliary and central retinal arteries demonstrated decreased velocities. In addition, Gosling's pulsatility index was increased for the central retinal artery but not the ophthalmic or short posterior ciliary arteries. Thirteen eyes improving in visual acuity and field after ONSD demonstrated significant improvement in all color Doppler imaging parameters for the short posterior ciliary arteries. The ophthalmic artery diastolic velocity also increased significantly but the central retinal artery parameters did not change. The eyes that remained stable or worsened did not demonstrate significant postoperative changes. CONCLUSION: These results suggest that some of the visual loss from chronic papilledema may be due to ischemia, and worsening visual acuity correlates with greater impairment of the retrobulbar circulation. One of the mechanisms by which ONSD improves visual function may be reversal of this ischemic process.

Arteries↗
PubMedDate not supplied

Controversies in the management of open-globe injuries involving the posterior segment.

There are numerous unresolved issues and controversies regarding the management of open-globe injuries involving the posterior segment. These areas include, but are not limited to, the following issues. Although vitrectomy has been shown to improve visual outcomes and allow retention of the eye in many cases, the extent of visual improvement is often limited because of the nature of the injury. Timing of vitrectomy surgery has been and will continue to be debated by proponents of early versus delayed intervention. The multiple features of acute ocular injury make it very difficult to interpret retrospective data regarding the most appropriate timing for surgical intervention. The use of prophylactic cryotherapy, in the setting of a scleral laceration with possible retinal damage, is not as controversial at present, as there is now sufficient data indicating that cryotherapy may actually exacerbate intraocular proliferation and worsen the situation. The role and benefit of a prophylactic scleral buckle is very widely contested, and it is not known if it truly decreases the risk of subsequent retinal detachment. Another area of debate centers on the use of antibiotics. When there is a known clinical infection, intravitreal antibiotics are the mainstays of therapy. However, in the absence of clinical infection, the use of prophylactic antibiotics and their routes of administration are quite controversial. Although there are significant data regarding the use of antibiotics in the postoperative setting, this information cannot be extrapolated into the setting of open-globe injuries, as organisms and virulence factors differ. Similarly, the use of vitrectomy versus vitreous tap in the setting of traumatic endophthalmitis is not fully resolved, although vitrectomy is used in most cases to repair concurrent damage from the injury itself. Finally, the placement of intraocular lenses in the acute trauma setting is controversial, as the risk of complications is quite high. Prospective, controlled clinical studies have not been done. This article reviews pertinent data regarding these management issues and controversies, and provides recommendations for treatment based on the available published data and the authors' personal experience.

Cryotherapy↗
PubMedDate not supplied

Follow-up of argon laser trabeculoplasty: is a day-one postoperative IOP check necessary?

BACKGROUND AND OBJECTIVES: To evaluate the benefit of measuring the intraocular pressure (IOP) on the first postoperative day after argon laser trabeculoplasty (ALT). PATIENTS AND METHODS: We retrospectively reviewed 407 ALT procedures with perioperative apraclonidine performed on 226 patients between January 1991 and December 1993. Data analyzed included type of glaucoma, extent of treatment, whether the procedure was initial or repeat, laser parameters, and IOP preoperatively and at 1 hour, 1 day, and 1 month postoperatively. RESULTS: The percentage of patients with an IOP rise of greater than 3 mm Hg at 1 hour, 1 day, and 1 month following ALT was 11.3%, 4.2%, and 5.2% respectively. The incidence of IOP elevations greater than 10 mm Hg was 2.2%, 1.0%, and 1.5% at 1 hour, 1 day and 1 month, respectively. Of 17 cases with an IOP elevation greater than 3 mm Hg at 1 day, four eventually required a trabeculectomy. However, there were no consistent factors that distinguished which cases with elevated IOP at 1 day ultimately needed further therapy, nor did the 1-day postoperative examination predict which patients would have IOP elevation at 1 month. CONCLUSION: IOP 1 day after ALT is rarely elevated and does not correlate with IOP elevation at 1 month. Therefore, an IOP check at 1 day is not felt to be necessary for most patients.

Adrenergic alpha-Agonists↗