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Modified trab yields high success rate, study shows
Surgeon removes a perpendicular scleral strip with trabecular meshwork.
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A study of patients undergoing a modified trabeculectomy confirmed what Dilip D. Pandit, MS, said he has known for 20 years: Removing a perpendicular flap of sclera along with the trabecular meshwork increases the procedure’s success rate.
“Usually the trabeculectomy fails because of the fibrosis,” Dr. Pandit said, recalling how he developed the technique 2 decades ago. “So there has to be a continuous drainage of the aqueous to have a perfect antiglaucoma surgery.”
The answer, he realized, lay in the creation of a tunnel that would run through the sclera to the anterior chamber through the trabecular meshwork, which would still be removed as in a traditional trabeculectomy.
“As there is continuous drainage of fluid through this tunnel, fibrosis does not occur,” said Dr. Pandit, who performs the technique in his practice in Mumbai, India.
He and colleagues published results of a clinical study of the technique in the Asian Journal of Ophthalmology.
Methods
Fifty patients who underwent the modified procedure were followed every 3 months for the first 2 years of the study and then annually for 3 more years. Dr. Pandit noted that, even though he has been performing the procedure for approximately 20 years, good long-term data had not been previously obtainable among the patients he treated.
In the modified technique, surgeons create two scleral flaps, removing the second flap to create a continuous passageway for aqueous.
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(Pictures captured from video recording, courtesy Dilip D. Pandit, MS.) | ||||
“Once we reach the level of the surgical limbus, below the second flap, we enter the anterior chamber and cut the trabecular meshwork so it forms a tunnel,” he said.
Sutures help to form the tunnel; the first scleral flap is sutured at two corners with 8-0 Ethicon sutures, which allows continuous aqueous drainage, Dr. Pandit said.
The procedure concludes with a peripheral iridectomy and tenonectomy. The excision of a portion of Tenon’s capsule ensures that the superior end of the tunnel remains open, he said.
Results
The surgeons did not modify the procedure according to the type of glaucoma or the severity of IOP. Dr. Pandit said chronic glaucoma was the most common type of glaucoma, seen in 86% of study patients.
No patient required antimetabolites intraoperatively or postoperatively, Dr. Pandit said.
During the 5-year follow-up in the study, 90% of patients achieved IOP results below 20 mm Hg. Four of the five remaining patients saw their pressure reduced by roughly half from a preoperative range of 41 mm Hg to 60 mm Hg.
Dr. Pandit reported that the mean postop IOP was 19 mm Hg compared to 39 mm Hg preop. Ninety-two percent of patients required no further medication.
“The bleb is diffuse, away from the cornea, and it does not irritate the patient,” he said, noting that 90% of patients had a diffuse bleb, 4% had a prominent bleb and 6% had a minimal bleb.
No complications
Visual acuity and cup-to-disc ratios remained stable in all 50 patients.
“There were no complications except sometimes the shallow [anterior chamber that] forms within a week or so,” Dr. Pandit said.
| Technique | |
| The technique used by Dr. Pandit and colleagues is described in a paper published in the Asian Journal of Ophthalmology. A conjunctival flap is dissected toward the limbus from a distance of 7 mm to 8 mm away. Two scleral flaps are created, each of one-third thickness, to perform the modified trabeculectomy. The first scleral flap measures 4 mm perpendicular and 6 mm parallel to the limbus. Dissection of the second flap begins 1 mm above the upper margin of the first flap; this second flap is removed before surgeons enter the anterior chamber. The technique proceeds with the removal of the trabecular meshwork. Surgeons then perform a peripheral iridectomy. Closure begins with suturing of the first flap. Tenon’s capsule is dissected from the conjunctival flap, a tenonectomy is performed, and the conjunctiva is closed with a continuous suture. |
Two of 30 patients with preop pressures between 20 mm Hg and 30 mm Hg had a postop IOP of less than 10 mm Hg, he said.
The researchers reported that the modified procedure can reduce surgeons’ dependence on antimetabolites. Dr. Pandit said the long-term safety and efficacy of antimetabolites has yet to be determined.
Dr. Pandit told OSN he no longer performs traditional trabeculectomy. He estimated that the learning curve is roughly 1 month before surgeons become experienced with his version of the procedure.
“The dissection of the second flap is a delicate process because one has to be meticulous and the depth of the scleral thickness has be judged properly,” he said. “But with experience … it is not difficult. One has to be very delicate [and] meticulous, and within a month or so, one can always learn that.”
For Your Information:Reference:
- Dilip D. Pandit, MS, can be reached at the Department of Ophthalmology, Mumbai Port Trust Hospital, Wadala, Mumbai 400 037 India; +91-22-414-5100; fax: +91-22-414-5115; e-mail: cmombpt@bom3.vsnl.net.in or drdilippandit@yahoo.co.in.
- Pandit DD, Unercat SB, Navelkar SS. Modified trabeculectomy: Follow-up study. Asian J Ophthalmol. 2003;5:3-7.