March 2011

 

COVER FEATURE

 

Combined Surgery

Glaucoma drainage devices have increasing role in advanced disease


by Jena Passut EyeWorld Staff Writer
 

 

A Baerveldt drainage device and Ahmed drainage device implanted inferiorly, at varying degrees of magnification Source: Leon W. Herndon, M.D.

Placement of the EX-PRESS Glaucoma Filtration Device Source: Alcon

When patients develop a cataract and glaucoma, often surgeons' first line of defense is to combine phacoemulsification and trabeculectomy to extract the cataract and achieve adequate IOP control.

"If the patient has early glaucoma and a cataract, phaco combined with endoscopic cyclophotocoagulation or phaco combined with Trabectome (NeoMedix, Tustin, Calif.)may be good options," said Steven R. Sarkisian Jr., M.D., director of the glaucoma fellowship, Dean A. McGee Eye Institute, and clinical associate professor of ophthalmology, University of Oklahoma, Oklahoma City. "If the patient wants something more definitive, phaco combined with canaloplasty or the EX-PRESS Glaucoma Filtration Device (Alcon, Fort Worth, Texas) may be better, the latter option being especially useful if you really need to keep the patient off all medications."

For patients who have more advanced forms of glaucoma or who have had previous surgery failures, surgeons may opt to implant an aqueous drainage device. Two such devices are the Ahmed Glaucoma Valve (New World Medical, Rancho Cucamonga, Calif.) and the Baerveldt Glaucoma Implant (Abbott Medical Optics, AMO, Santa Ana, Calif.).

These procedures introduce a tube into the eye that carries aqueous humor from the inside of the eye to a reservoir implanted under the conjunctiva. They can be performed alone or in a combined phaco procedure.

Iqbal (Ike) K.Ahmed, M.D., assistant professor, University of Toronto, and clinical assistant professor, University of Utah, Salt Lake City, said the devices have long been a second-line or third-line option, but "there's a trend now for surgeons to go to these devices earlier."

Patients with neovascular glaucoma, extensive diabetic retinopathy, or aggressive uveitis are good candidates for the combined phaco-drainage device procedure. "They tend to scar more," Dr. Ahmed said, adding that patients with a poor conjunctiva or who have failed initial surgery would benefit as well.

For his part, Thomas W. Samuelson, M.D., attending surgeon, Minnesota Eye Consultants, Minneapolis, and adjunct associate professor, University of Minnesota, reported doing fewer combined glaucoma procedures than he has in the past. "The accumulating data that phacoemulsification lowers IOP has led me to utilize cataract surgery as an incremental step in glaucoma management, especially if the disease is mild and the patient has disc and visual field reserve," he said.

Simply removing the cataract often adequately lowers IOP if the glaucoma is mild or moderate. Dr. Samuelson said he can then reassess and move on to more aggressive glaucoma management if needed. "I believe this 'minimalist' approach reduces risk and takes no option off the table," Dr. Samuelson said. "Importantly, it is the option that I would want if I were the patient, at least at this point in time."

If the disease is more advanced or the patient has failed previous incisional glaucoma surgery, Dr. Samuelson will move on to a combined procedureeither phaco with trabeculectomy or with an aqueous drainage device such as the Baerveldt implant. "Combined surgery in this setting is a terrific opportunity to improve visual function and stabilize IOP," Dr. Samuelson said. "I am very enthusiastic about the intense interest in minimally invasive glaucoma surgery techniques currently in trials such as the iStentTrabecular Micro-Bypass (Glaukos, Laguna Hills, Calif.), as well as available techniques such as Trabectome. As less invasive and safer procedures become available, the opportunity to combine surgical procedures will expand to those with less advanced disease." Surgeons are using the drainage devices more for advanced glaucoma, citing their long-term efficacy and reduced risk of infection.

Dr. Ahmed's colleague, Nir Shoham, M.D., will present a paper at the ASCRS•ASOA Symposium & Congress in San Diego that compares cataract extraction with the two drainage devices.

"This retrospective, single surgeon study of 66 eyes compared outcomes of combined phacoemulsification with either Ahmed Glaucoma Valve (N=41) or Baerveldt Glaucoma Device (N=25)," according to the abstract. "Surgical success was defined as reduction in intraocular pressure (IOP) >20%, an absolute 5 mm Hg ≤ IOP ≤ 18 mm Hg, with or without glaucoma medications, no loss of light perception, no vision threatening complications and without further glaucoma surgery."

The mean IOP and glaucoma medications after 1 year were comparable between the two groups, although the phaco/Baerveldt group had a significantly higher IOP than the phaco/Ahmed group at 1 day (p<0.001) and 1 week (p<0.001) and a higher use of glaucoma medication classes at 1 week (p<0.001) and 1 month (p<0.001).

Survival rates after 1 year were 80.5% with the Ahmed and 80% with the Baerveldt (p=0.839). There was no difference in complication rates (p=0.699) or improved visual acuity, maintained visual acuity, and loss of visual acuity between the two groups.

There also was no significant difference in the intraocular pressure control, success rate, visual outcomes, and complication rates between the phaco/Ahmed and the phaco/Baerveldt groups at 1 year after surgery. However, the phaco/ Baerveldt group required a greater number of post-op interventions (p=0.022).

In response to the rising use in tube shunts, the Trabeculectomy Versus Tube study was conducted to compare complications and outcomes between patients. Patients who had previously undergone failedtrabeculectomyor cataract surgery and required surgery for IOP control were randomized to undergo eithertrabeculectomywith mitomycin-C or implantation of a non-restrictive Baerveldt implant. The 5-year study enrolled patients from 1999 to 2003. It included 212 patients between ages 18 and 85 who had an IOP between 18 mm Hg and 40 mm Hg, and who had previous trabeculectomy, cataract explantation with IOL implantation, or both. After 1 year, non-valved tube shunt surgery was found to be more likely to maintain IOP control and avoid persistent hypotony or reoperation for glaucoma than trabeculectomy with MMC. Three-year outcome data from the TVT study was reported in Current Opinion in Ophthalmology.

According to the abstract, the intermediate-term results of the multicenter, randomized clinical trial supports the use of tube shunts, even beyond refractory glaucoma.

"Tube-shunt surgery is an appropriate surgical option in patients who have undergone prior cataract and/or unsuccessful filtering surgery," the study found. Trabeculectomy rates in the TVT study were twice as high as for tubes, with 30% of trabs failing within 3 years, compared to 15% of tubes. Failure was defined as IOP being too high (>21 mm Hg) or too low (<5 mm Hg), the need for reoperation, or loss of light perception vision. Post-op, wound leaks and dysesthesia were more common in the trabeculectomygroup, while post-op diplopia was more common in the tube group.

Dr. Sarkisian said he removes the cataract before moving on to the shunt implantation in the pars plana.

"It's a very rewarding opportunity when a patient has had a previous vitrectomy and there might be scarring of the conjunctiva," he explained about the positioning of the device. "Then the tube has no chance of coming in contact with the cornea.

"The refractive result is not going to be as impressive initially as it would be when doing the cataract surgery alone," he continued. "IOP control is paramount. You don't want to have inflammation from cataract surgery."

References

1. Gedde SJ, Schiffman JC, Feuer WJ, et al. The Tube Versus Trabeculectomy Study: Design and baseline characteristics of study patients. Am J Ophthalmol 2005;140:275287.

2. Gedde SJ, Schiffman JC, Feuer WJ, et al. Treatment outcomes in the Tube Versus Trabeculectomy Study after one year of follow-up. Am J Ophthalmol 2007;143:922.

3. Minckler DS, Francis BA, Hodapp EA, et al. Aqueous shunts in glaucoma: A report by the American Academy of Ophthalmology. Ophthalmology 2008;115:10891098.

4. Wilson MR, Mendis U, Smith SD, Paliwal A. Ahmed glaucoma valve implant vs. trabeculectomy in the surgical treatment of glaucoma: A randomized clinical trial. Am J Ophthalmol 2000;130:267273.

5. Tsai JC, Johnson CC, Dietrich MS. The Ahmed shunt versus the Baerveldt shunt for refractory glaucoma: A single surgeon comparison of outcome. Ophthalmology 2003;110: 18141821.

Editors' note: Dr.Ahmedhas financial interests with AMO. Dr. Samuelson has financial interests with AMO, AcuMems (Menlo Park, Calif.), Alcon, Allergan (Irvine, Calif.), AqueSys (Irvine, Calif.), Endo Optiks (Little Silver, N.J.), Glaukos, iScience (Menlo Park, Calif.), Ivantis (Irvine, Calif.), Pfizer (New York), QLT (Menlo Park, Calif.), and Santen (Napa, Calif.). Dr. Sarkisian has no financial interests related to his comments.

Contact information

Ahmed: 416-625 3937, ike.ahmed@utoronto.ca
Samuelson: 612-813-3628, twsamuelson@mneye.com
Sarkisian: 405-271-1093, Steven-Sarkisian@dmei.org

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