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Viscoelastic may reduce corneal toxicity from 5-fluorouracil
Using a Healon bolus gets 5-FU away from the cornea and into the trabeculectomy, where it needs to be.
BARCELONA, Spain — Using a bolus of Healon to form a barrier between the cornea and the site of a trabeculectomy may reduce the toxicity seen after antimetabolites injection, according to two researchers.
George L. Spaeth, MD, FACS, director, glaucoma service, Wills Eye Hospital in Philadelphia, and Peng T. Khaw, PhD, FRCP, FRCS, FRCOphth, FRCPath, of the ocular repair and regeneration biology unit, Institute of Ophthalmology and glaucoma unit, Moorfields Eye Hospital in London, are studying the new method to draw conclusions about its efficacy.
Dr. Spaeth presented the results of a small-scale study of antifibrosis therapy in conjunction with glaucoma filtration procedures at the International Glaucoma Symposium here.
Corneal toxicity
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The problems with antimetabolites are documented in the literature, Dr. Spaeth said. Richard Parrish, MD, published a study in the American Journal of Ophthalmology that addressed 5-years follow-up results. That paper concluded the major problems with 5-fluorouracil include the inconvenience of twice-weekly injections, as well as corneal toxicity.
Dr. Khaw told Ocular Surgery News. “This happens mainly because the 5-FU leaks into the tear film via the injection site that was used to enter subconjunctivally in the first place. To negate this I developed this technique.”
Dr. Khaw said he injects Healon GV subconjunctivally, then injects 5-FU through the Healon GV, thus placing the “Healon wall” between the 5-FU and the injection hole.
“This stops the 5-FU from leaking out through the tear film causing the corneal epithelial problem,” he said. “Also, because it delays the flow of 5-FU into the tear film, the 5-FU lasts much longer. It needs to work at the site of the trabeculectomy.”
“I introduced Dr. Spaeth to the idea at the Association for Research and Vision in Ophthalmology meeting 2 years ago, based on some simple experimental studies,” Dr. Khaw continued. “I did it to try to develop a slightly longer-acting 5-FU technique. I have actually used this technique for several years now. After hearing about the technique, Dr. Spaeth went back and did his own series of cases, and then very kindly included me in on the study and discussions with him.”
Observational series
Dr. Spaeth conducted an observational series of 17 cases using the guarded filtration procedure. The eye was anesthetized topically. A 30-gauge needle on a vial of Healon GV was introduced into the inferotemporal conjunctiva 5 mm inferior to the limbus. A bolus of 0.2 mL of Healon was injected, followed by 0.3 mL of 5-FU with a concentration of 50 mg/mL, injected with a 30-gauge needle entering through the bolus of Healon.
One injection of 0.3 mL of 5-FU was administered, with follow-up injections as needed. Dr. Spaeth collected data on patient comfort, condition of the cornea and success as determined by postop IOP without serious complication.
The 5-FU injection was repeated one to three times, between 3 and 5 days postop, where deemed appropriate. In the study, 14 patients received one injection, 10 cases received two injections and two cases required three injections, according to Dr. Spaeth’s presentation.
One patient developed mild superficial punctate keratitis after the first injection that persisted for less than 7 days. No patient reported discomfort of any level.
Surgically, 13 patients were deemed a success, seven were considered partial successes and six were considered failures.
Dr. Spaeth concluded that postop 5-FU given as per Dr. Khaw appears to be safe and perhaps effective.
“At the moment, we are looking at the procedures before and after the Healon GV technique,” Dr. Khaw said. “Essentially, the further research that needs to be done to prove that the method works is to do a full experimental study and a randomized trial doing normal 5-FU vs. the new method for both efficacy and side effects.”
For Your Information:Reference:
- Peng T. Khaw, PhD, FRCP, FRCS, FRCOphth, FRCPath, is the professor of ocular healing and glaucoma studies and a consultant ophthalmic surgeon at the ocular repair and regeneration biology unit, Institute of Ophthalmology and the glaucoma unit, Moorfields Eye Hospital. He can be reached at 11-43 Bath St., London EC1V 9EL; phone/fax: (44) 20-7608-6887; e-mail: p.khaw@ucl.ac.uk; Web site: www.ucl.ac.uk/ioo/research/khaw.htm.
- George L. Spaeth, MD, FACS, Louis Esposito Research Professor, can be reached at Wills Eye Hospital, 840 Walnut St., Philadelphia, PA, 19107. (215) 928-3197, fax: (215) 928-0166, e-mail: gspaeth@willseye.org.
- Parrish RK II, Schiffman JC, et al. Prognosis and risk factors for early postoperative wond leaks after trabeculectomy with and without 5-fluorouracil. Am J Ophthalmol. 2001;132:633-640.