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Trabeculectomy an option in early treatment for severe glaucoma
Consider using filtration surgery as initial therapy in patients with advanced glaucoma for rapid and significant IOP lowering, doctor recommends.
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Trabeculectomy can reduce IOP significantly in advanced glaucoma with minimal risk, and it should be considered as a first-line treatment in those cases, a presenter at Hawaiian Eye 2007 said.
Philip P. Chen, MD, said although medications and laser trabeculoplasty are effective in treating glaucoma as initial therapy, there is also a role for trabeculectomy as first treatment in advanced cases. He said trabeculectomy reduces IOP faster and, potentially, for a long period of time. It also reduces IOP variability and treatment adherence issues, he said.
“Trabeculectomy for advanced glaucoma is, I believe, a reasonable initial treatment,” Dr. Chen said. “It provides low IOP for those who need it the most. It is reasonably well-supported by randomized trials. The risk is finite, but small, and techniques can be used to minimize it.”
Because experience is key to performing successful trabeculectomies, Dr. Chen said the procedure might not be the best option for all doctors to pursue. For those who do, several studies have supported the use of filtration surgery as initial therapy to reduce pressure.
Early studies
One of the first studies to look at medication vs. trabeculectomy was the Moorfields Glaucoma Trial, which was initiated in 1968 in England. It randomly assigned 52 patients to either medications available at the time or glaucoma surgery consisting of a modified Scheie procedure.
At 6 to 8 years follow-up, the surgical group had statistically significant greater IOP reduction by 5.6 mm Hg and less visual field loss, Dr. Chen said.
In the 1980s, a study was done in Glasgow, Scotland, using the newer surgery available, trabeculectomy. It randomly assigned 116 patients who received trabeculectomy or medical treatment, which included timolol. Nearly 5 years later, IOP reduction in the trabeculectomy group was significantly greater, by 5.8 mm Hg. There was significantly less visual field loss in the surgery group, yet visual acuity and cataract formation were equal in both groups.
Beginning in 1983, the Moorfields Primary Treatment Trial was conducted to examine the results of medication vs. trabeculectomy. The study randomly assigned 168 patients to medication, surgical and laser groups. It found that at 5-year follow-up, the medication group was most likely to fail, Dr. Chen said.
The surgical group had significantly greater reduction of IOP at 5 years, by 6 mm Hg, Dr. Chen said. At 2-years follow-up, the surgical group also had less visual field loss compared with the medication group, although after that point there was no difference.
Later studies
 Philip P. Chen |
In 1993, U.S. researchers, led by Paul Lichter, MD, began the Collaborative Initial Glaucoma Treatment Study (CIGTS), Dr. Chen said. The study randomly assigned 607 patients into two groups. Patients in the medication group received maximum medications, followed by laser trabeculoplasty; patients in the surgery group received trabeculectomy, followed by laser trabeculoplasty and medications if needed.
At 5 years, the medication group was more likely to need laser trabeculoplasty, Dr. Chen said. The IOP was not statistically different between the two groups. However, Dr. Chen said those results were predictable, as both groups were treated at the same target IOP. There was no difference in visual field loss between the two groups as a whole, he said.
The CIGTS results might have been different from the British studies for multiple reasons. The racial characteristics in the American study could be one factor, with 44% of the study population being nonwhite patients, whereas in the British studies the nonwhite population ranged from zero to 12%, Dr. Chen said. In CIGTS, but not the British studies, IOP was treated to a target level for both surgical and medical arms.
In addition, IOP and visual field loss were lower for the CIGTS, with a mean starting IOP of 27 mm Hg, and most patients having early field loss. The British studies had higher average starting IOPs and more severe visual field loss, Dr. Chen said. The Glasgow study had average starting IOP of 36 mm Hg, with 100% of patients having moderate or severe visual field loss; Moorfields had mean starting IOP of 35 mm Hg, with 48% of patients having severe visual field loss.
Quality of life
Of the studies described above, only the CIGTS measured patients’ quality of life, Dr. Chen said. In telephone interviews at 5 years, it found that patients who had surgery were significantly more likely to complain of eye pain and problems with activities related to visual acuity.
“It might not be a great thing to push surgery on these patients with early disease who have little functional loss from their glaucoma and who may not even notice that they have it at all,” Dr. Chen said. “But possibly patients with more severe disease who have noticed some functional loss would be more willing to accept some of these risks in trade for having better control of their glaucoma long term.”
He said trabeculectomy’s main risks, bleb-related problems, could be reduced by altering surgical technique. He tries to reduce the risk of bleb leak and encourage posterior aqueous flow by using thin sponges to apply mitomycin that extend beyond the conjunctival incision line, in limbus-based trabeculectomy. He emphasized the importance of educating patients about infection after trabeculectomy. The best way to prevent vision loss from endophthalmitis is to treat it while it is still blebitis, he said.
Placing the scleral flap at 12 o’clock may reduce the risk of bleb-related pain. He also aims for low target IOP postop, to help prevent failure due to loss of IOP control.
“If they’re phakic, I like to aim even lower than I would typically aim, knowing that phaco after trabeculectomy will typically raise IOP 2 mm Hg or 3 mm Hg,” he said. “And I’m fairly aggressive with suture lysis and needling with antifibrosis agents.”
For more information:
- Philip P. Chen, MD, is associate professor and acting chairman at the department of ophthalmology, University of Washington, and chief of ophthalmology at the University of Washington Medical Center. He can be reached at 1959 NE Pacific St., Seattle, WA 98195; 206-543-9081; fax: 206-543-4414; e-mail: pchen@u.washington.edu.
References:
- Jay JL, Allan D. The benefit of early trabeculectomy versus conventional management in primary open angle glaucoma relative to severity of disease. Eye.1989;3:528-535.
- Lichter PR, Musch DC, et al; CIGTS Study Group. Interim clinical outcomes in the Collaborative Initial Glaucoma Treatment Study comparing initial treatment randomized to medications or surgery. Ophthalmology. 2001;108:1943-1953.
- Migdal C, Gregory W, Hitchings R. Long-term functional outcome after early surgery compared with laser and medicine in open-angle glaucoma. Ophthalmology. 1994;101:1651-1656.
- Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.