April 2012

 

GLAUCOMA

 

Glaucoma editor's corner of the world

Torics: A viable premium option for glaucoma patients


by Jena Passut EyeWorld Staff Writer

 

Toric lenses enable surgeons to help patients with even high degrees of astigmatism to achieve emmetropia with cataract surgery. As with all new cataract technology, surgeons may be reluctant to use toric IOLs in glaucoma patients. But some trailblazing surgeons are demonstrating that glaucoma patients may be excellent candidates for toric lenses. This month we are fortunate to have Steven Sarkisian, M.D., and Kathryn Friedl, M.D., give their insights on how much toric IOLs can help glaucoma patients. Glaucoma patients present surgeons with a variety of challenging situations involving toric lenses. The pseudoexfoliation patient may have questionable zonuleshow will this affect placement of the toric lens and long-term stability? Patients with blebs often have high degrees of astigmatism, but will it be stable after cataract surgery? What if the pressure rises and more glaucoma surgery is necessary? Dr. Friedl and Marlene Moster, M.D., are using toric lenses in cataract surgery combined with a trabeculectomy. Combined surgery is a very uncertain situation because the pressure may be variable, and the impact of the trabeculectomy flap on the astigmatism is an issue. The willingness of these courageous surgeons to confront these challenges helps all surgeons as well as glaucoma patients. Glaucoma patients want to see clearly without glasses like other cataract patients. The primary goal of glaucoma therapy is not reducing eye pressure; it is maintaining the best possible vision. Drs. Friedl and Sarkisian deserve our gratitude for showing us how best to use toric IOLs in our glaucoma patients.

Reay Brown, M.D., glaucoma editor

 

Source: Stockbyte/Stockbyte/Getty Images

A glaucoma patient, especially one who has significant visual field loss, likely won't be able to take advantage of multifocal lens implants during cataract surgery.

Toric lenses, on the other hand, are a viable premium option and commonly used, according to two surgeons who spoke to EyeWorld.

"I place several toric lenses every week because of the great advantage they bring patients, regardless of whether or not they have glaucoma," said Steven R. Sarkisian Jr., M.D., clinical associate professor of ophthalmology, Dean McGee Eye Institute, University of Oklahoma College of Medicine, Oklahoma City. Toric lenses play a unique role in patients with glaucoma because of the astigmatism that can be induced by glaucoma surgery, Dr. Sarkisian said.

"Conventional trabeculectomies tend to induce a significant amount," Dr. Sarkisian said. "Some of our newer procedures likely induce less astigmatism, but every time you're creating a reservoir, you have that possibility of astigmatism."

Dr. Sarkisian said surgeons should want their glaucomatous patients to have the best refractive results possible.

"Surgeons should not suspend desire for optimum visual outcomes just because the patient has glaucoma," he said.

Kathryn B. Freidl, M.D., associate professor of ophthalmology, Shands at the University of Florida, and in private practice, Florida Eye Specialists, Jacksonville, agreed that multifocal lenses might not be the best route.

"You want to make sure the glaucoma patient has good central vision and visual acuity potential," Dr. Friedl advised. "With multifocal lenses, there's a concern about visual field loss. That same concern doesn't apply to the toric lenses as long as the patient has good central vision without fixation loss."

Dr. Friedl undertook a case study of about 100 surgical patients of Marlene Moster, M.D., attending surgeon, Glaucoma Service, Wills Eye Institute, and professor of ophthalmology, Thomas Jefferson University, Philadelphia.

In the study, which has not been published, Dr. Friedl compared the anticipated astigmatism versus what astigmatism developed post-op after toric lenses were implanted in patients.

The patients either underwent a straight cataract surgery or the surgery was combined with a trabeculectomy procedure.

"When you're doing trabs, you can have an issue post-operatively with the lens moving anterior because of overfiltration," Dr. Friedl said. "The concern would be how much of that is going to affect the overall outcome."

Dr. Friedl said she discovered that both anticipated and residual astigmatism numbers were closewithin a half or quarter diopter, "which is the same as what's in the literature in standard cases."

Dr. Friedl said there were cases in which the lens did flatten or come all the way forward, but the patient still had 20/20 visual acuity with the lens. "It didn't necessarily affect the axis rotation, or if it did, it wasn't enough to throw off the acuity," she said.

To minimize the potential for more astigmatism, Dr. Friedl said a surgeon should make sure the eye is firm before opening a trab flap or suturing the trab. "Sometimes in a trab we like to close when the eye is softer because you get a little more tightness to your wound, but that can induce more astigmatism, so you would alter your technique that way," she said. Dr. Sarkisian said he takes a conservative approach to combined procedures because of the possibility of inducing astigmatism during filtration surgery.

"I typically am not doing combined toric and filtration surgery unless a patient has a large amount of astigmatism in the horizontal axis," he said. "If the patient has 2.5-3 D of astigmatism in the horizontal axis, then I will consider combined surgery."

Dr. Sarkisian said he does combine the toric procedure with endoscopic photocoagulation or insert the toric lens during a phacocanaloplasty or newer minimally invasive glaucoma surgery, such as the iStent Trabecular Micro-Bypass (Glaukos, Laguna Hills, Calif.) or EX-PRESS Glaucoma Filtration Device (Alcon, Fort Worth, Texas). The iStent is awaiting FDA approval. In combined procedures, Dr. Sarkisian offered advice to minimize the chances of surgically induced astigmatism.

"Sutures that are too tight are the primary culprit," he said. "Be careful not to tie sutures too tightly close to the cornea. Also, over cauterization near the limbus can cause surgically induced astigmatism, too."

Bleb height also may be a factor, Dr. Sarkisian added. "There's not much you can do about that except wait for the bleb to remodel, and often the astigmatism diminishes with time," he said.

Using a "one punch only" technique with a trabeculectomy to create a smaller fistula may reduce residual astigmatism, Dr. Sarkisian noted.

The smaller fistula reduces outflow, which means surgeons will not have to tie flap sutures as tightly, he said.

Dr. Sarkisian said he also uses a pointy-tipped cautery that uses less energy and allows the surgeon to focus in on active bleeding sites.

Dr. Friedl said marking the eye is critical.

"If you're doing a combined phaco/trab, make sure you have every axis marked before you make your entry into the anterior chamber under the trab flap," she said. "Make sure the eye is nice and full."

Toric lenses can be placed in pseudoexfoliation patients, but extra steps must be taken, Dr. Friedl said. "In order to maintain capsular support, you might need to stabilize the capsule with a Mackool hook," she said. A nearly perfect rhexis would be ideal, too.

"These patients are more prone to capsular phimosis or the contraction of the capsule if the rhexis is too small," she said. "You want the optic contained in the rhexis, but you don't want it too small that it is increasing the risk of capsular phimosis."

Editors' note: Drs. Friedl and Sarkisian have no financial interests related to this article.

Contact information

Friedl: kfreidl@gmail.com
Sarkisian: steven-sarkisian@dmie.org

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