Cataract and glaucoma don't go together like a horse and carriage

[June 2011 EyeWorld]

Cataract and glaucoma don't go together like a horse and carriage

by Matt Young EyeWorld Contributing Editor

There are problems treating both diseases in the same patient, but modern solutions exist

    A new report refers to cataract as the "silent enemy" in relation to glaucoma and trabeculectomy surgery, and it's no wonder why. In a nutshell, cataract formation is likely after trabeculectomy surgery. Subsequent cataract surgery leads to frequent bleb failure. Cataract surgery in patients requiring filtration surgery remains an issue of contention, according to the report, published online in January in the British Journal of Ophthalmology. "Cataract should not remain the silent enemy of successful trabeculectomy surgery," lead author Rashmi G. Mathew, M.R.C.Ophth., Moorfields Eye Hospital, London, said in the report. "Reviewing the literature does provide clarity on some issues surrounding this topic."

   It's also important to combine the research with practical experience. How are real-world glaucoma surgeons dealing with these issues? EyeWorld presented these research-derived dilemmas to ophthalmologists and asked: How do you operate on glaucoma patients today?

Examining the evidence


   After trabeculectomy surgery, patients require cataract surgery between 20% and 52% of the time and up to 7 years post-op, Dr. Mathew noted. Research has shown cataract rates after trabeculectomy surgery are higher than in control eyes. The Collaborative Initial Glaucoma Treatment Study—one of the largest studies comparing medical and surgical intervention in glaucoma patients—concluded that trabeculectomy surgery "placed a patient at an increased risk of cataract for a moderate amount of time, after which other factors such as aging played a more important role." If cataract does develop thereafter and requires surgery, 10-61% of trabeculectomies fail between 12 and 36 months post-op. In one case-control study, 24% of trabeculectomies failed that underwent cataract extraction, while only 7% failed that did not undergo cataract extraction, Dr. Mathew reported. For surgeons interested in treating both the cataract and glaucoma problem at the same time, it's not so easy.

   "[An earlier study] compared 100 trabeculectomies with 200 phacotrabeculectomies, and found that trabeculectomy alone resulted in a larger decrease in IOP than the combined procedure," Dr. Mathew reported. At 1 year, IOP in the trabeculectomy alone group was 15.2 mm Hg, while it was 18.7 mm Hg in the combined group. "These have been long-standing problems in glaucoma management," said Phillip McGeorge, M.D., Perth, Australia. After hearing the research evidence, Dr. McGeorge stated his practical resolutions to these problems. "My standard treatment given severe glaucoma is to do the trabeculectomy first," Dr. McGeorge said. "This provides good [IOP] control. Subsequently, when necessary, I perform cataract surgery." Dr. McGeorge said combined phacoemulsification and glaucoma surgery is "convenient, but it should not be used routinely for all cataract patients who have some glaucoma or severe glaucoma patients with early cataract." "There is good reason to minimize the number of things you have to do to an eye," Dr. McGeorge said. "There has been some improvement in the combined procedure, but the results are not as good as separate procedures. It may still provide adequate IOP control in the short term."

   Could a surgeon perform cataract surgery first and trabeculectomy later? "Absolutely; it depends on what is indicated at the time" Dr. McGeorge said. "You might get a spike in IOP associated with the cataract procedure. That can cause some further visual field loss if advanced glaucoma exists." But for patients at an earlier stage of glaucoma, this is an option, he said. David DeRose, M.D., Lehigh Eye Specialists, Allentown, Pa., takes a different approach. He addresses cataract relevant to glaucoma from case to case, depending on nuclear density. "If the patient is on the younger side and doesn't have much of a cataract, I try to do just the trabeculectomy," Dr. DeRose said. "If the patient is on the older side and/or has advanced glaucoma, I'll do the combined procedure. Those patients are at their max meds and aren't getting any better. You don't want to subject them to more than one procedure because they're older."

   That's a good point, Dr. McGeorge said. "Not many surgeons believe in loading up too many procedures on the eye if they can help it," Dr. McGeorge said. "All procedures have a certain complication rate."

   But Dr. DeRose acknowledged that a combined procedure often leads to mixed success. "Hopefully, you get everything in one swoop," he said. "I'm finding that if I do enough of these combined procedures, everything happens. Some combined procedures cause pressure to come down a little bit; other pressures come down a lot. There's a little bit of luck in everything."

   Sometimes, Dr. McGeorge said, if a patient has mild glaucoma, he will just perform cataract surgery. "At times, you get a lower pressure just with cataract surgery," Dr. McGeorge said. Nick Mamalis, M.D., John A. Moran Eye Center, University of Utah, Salt Lake City, gave wholehearted support to that idea. "We can often control glaucoma just by removing the lens," Dr. Mamalis said. "The reasoning makes good sense. If you're looking at the eye with an OCT scan, the lens gets thick as the cataract is forming. That tends to crowd the trabecular meshwork. Removing the lens itself gives a pressure reduction."

   This is especially true in patients who have pseudoexfoliation, Dr. Mamalis said. "If you do cataract surgery in patients with pseudoexfoliation and mild to moderately high pressure, the pressure may be controlled acutely and for the long term," Dr. Mamalis said. However, pressure reduction via cataract surgery is only for patients with moderate IOP increases and moderate glaucoma, he said. In cases of poorly controlled IOP or more severe glaucoma, Dr. Mamalis would favor a combined cataract/glaucoma procedure, which would give a much better IOP-lowering effect than cataract surgery alone. Dr. Mamalis agreed that trabeculectomy surgery can cause cataracts to progress, and cataract surgery thereafter can cause inflammation and lead to more bleb failures. There's clearly no single solution to the complex problem of eradicating both cataracts and glaucoma. A number of solutions and the order in which to perform them are available. The discerning surgeon will examine the evidence and decide what's best for his or her patients, or perhaps what's right for each patient individually.

Editors' note: The physicians mentioned have no financial interests related to their comments or research.

Contact information

DeRose: 610-820-6320, francesco26@me.com

McGeorge: +61 8 9388 0569, philm@perthlaservision.com.au

Mamalis: 801-581-6586, nick.mamalis@hsc.utah.edu

Mathew: rashmi.mathew@doctors.org.uk