December 2013

 

REFRACTIVE

 

Toric IOLs possible in glaucoma cases


by Erin L. Boyle EyeWorld Senior Staff Writer

   

Toric lenses can and should be considered in these patients for best refractive outcomes, with exceptions in certain cases

Toric IOLs can be effective and useful in some glaucoma patients for the correction of astigmatism, including those with stable disease, but should be considered with caution in other glaucoma cases, including those with pseudoexfoliation.

Glaucoma patients are just like other patients in the general population—they want good refractive outcomes and spectacle-free vision following surgery, experts say.

"For me, the final word on this is that glaucoma patients are not a separate group of people from refractive patients. Just like all humans, they enjoy spectacle independence and, in fact, maybe more so than other people. Every little bit that we can do to enhance their vision-related quality of life is of value," said Nathan Radcliffe, MD, assistant professor of ophthalmology, Weill Cornell Medical College, New York-Presbyterian Hospital, New York.

"We shouldn't discount this group of patients when we're trying to give them excellent refractive outcomes," he said. "And the toric IOL is a great way to do it because it doesn't operate on the cornea and it won't have any impact on IOP assessment, unlike corneal-based methods of eliminating astigmatism."

Jeffrey Kammer, MD, Vanderbilt Eye Institute, Nashville, Tenn., expressed a similar opinion. He said that glaucoma patients want sharp vision and no glasses, and in astigmatic cases, toric lenses can be an option. "For that reason, toric IOLs should be considered in any stable glaucoma patient with good potential visual acuity regardless of their field of vision," he said. He cautioned, however, that his statement "stands in contrast" to his recommendations for pseudoexfoliation patients who want multifocal IOLs.

"I would not place these lifestyle IOLs in this group of patients, particularly those with significant visual field defects, because they have the dual risk of IOL decentration and impaired contrast sensitivity, a double whammy that could lead to profound visual debilitation," Dr. Kammer said.

Indications

While there appears to be no significant differences in indications for glaucoma patients receiving a toric lens vs. healthy eyes, Dr. Radcliffe said, there are some considerations in this patient population before a toric IOL is chosen.

Dr. Kammer outlined those considerations as: • Is the patient's central vision impaired? • Is the patient's glaucoma stable? • Will the patient need glaucoma surgery in the near future and, if so, what type of surgery? • What type of glaucoma does the patient have? Patients who have a better chance of success are those who have had stable disease for at least six months, have IOP within the target range on one bottle or less of glaucoma medications, and are at least six months past a trabeculectomy with stable IOP and corneal measurements, Dr. Kammer said. Patients with primary open angle glaucoma or primary angle closure without evidence of trauma or pseudoexfoliation appear to be the best types of glaucoma subsets for toric IOL success. Regular astigmatism is also the best astigmatic correction in these patients, he said. In patients with filtering surgery-induced astigmatism, toric IOLs have been useful.

"Following conventional trabeculectomies, patients are often left with residual with-the-rule or, more appropriately, 'with the wound,' astigmatism. This may be due to a large bleb, tight sutures at the scleral flap or excessive cauterization of the sclera," Dr. Kammer said. "Regardless, studies have found that these patients are sometimes left with up to 2 D of astigmatism. Fortunately, for those patients who are ready for cataract surgery, this can be easily corrected with toric IOLs, thus enabling emmetropia and excellent vision," he said.

The central vision can be important in these cases if the fovea is affected by glaucomatous vision loss, according to Dr. Radcliffe. He said he has implanted a toric IOL in these patients, but managing patient expectations is important. He determines if the fovea is affected by testing foveal sensitivity, on either the Octopus or Humphrey visual field perimeters. He said the foveal sensitivity is sometimes turned off in the program, so the physician should check to ensure it is being measured. The normal level is generally 32 decibels.

"I would be hesitant to use a toric intraocular lens in a glaucoma patient with less than 28 decibels of foveal sensitivity, particularly if I had a concern that the glaucoma damage was affecting the center of vision," Dr. Radcliffe said. Newer optical coherence techniques that measure ganglion cell thickness in the macula can also be of assistance in determining whether glaucoma is threatening central vision.

Glaucoma cases implanted with toric IOLs during cataract surgery combine well with microincisional glaucoma surgeries, Drs. Radcliffe and Kammer said. Dr. Kammer would be wary of implanting a toric IOL in a combined phaco-trabeculectomy case, however.

Pseudoexfoliation, small pupils

In pseudoexfoliation glaucoma cases, whether to implant a toric lens is a matter of debate. These cases can pose challenges in a number of ways, Dr. Kammer said. Physicians must be able to deal with any issues that arise in these cases. Zonular weakness is a key issue. Intraoperatively, it is important to assess for the presence and extent of zonular laxity. If present, you must determine whether to proceed with toric IOL placement and, if so, whether a traditional CTR is needed. If more significant laxity is detected, you may even need to place one or more modified Cionni capsular tension rings or Ahmed capsular tension segments to stabilize the capsular bag by affixing it to the sclera, he said.

Dr. Kammer is most concerned about late onset of IOL dislocations that are secondary to progressive zonulopathy. This can lead to IOL decentration and rotation, he said. These can cause significant spherocylindrical changes, including higher order aberrations that impact vision.

"It is important to remember that you can see these complications despite the presence of a traditional capsular tension ring," Dr. Kammer said. "Regardless, you must have a proactive plan on how to deal with these issues if and when they occur."

An additional issue is the potential for capsular phimosis, which can induce IOL decentration, he said.

"You can go a long way toward preventing this from occurring by creating a generous capsulorhexis, roughly 5.5 mm, that still envelops the IOL. If phimosis does develop, it can often be treated by using the YAG laser to create a 2- to 3-mm cruciate incision at the 12, 3, 6, and 9 o'clock positions on the anterior capsule," Dr. Kammer said.

Patient education in these cases is important, and they should be informed of possible problems if they have weak zonules, for instance, Dr. Radcliffe said.

"The issue that can arise is a late in-the-bag IOL dislocation, so you may want to explain to the patient that particularly with a toric lens, if that lens does become dislodged, it's probably going to need to be removed and replaced," he said.

Small pupils in glaucomatous eyes can also pose challenges in toric lens implantation, both physicians said. Pupil expanders have greatly helped with small pupil cases.

"While we were once daunted by the case itself, these devices now provide an excellent view of the cataract with a stable pupil size, thus freeing us to focus on other surgical considerations, including toric IOL placement," Dr. Kammer said.

Editors' note: Dr. Radcliffe has financial interests with Alcon (Fort Worth, Texas), Allergan (Irvine, Calif.), Glaukos (Laguna Hills, Calif.), and Iridex (Mountain View, Calif.). Dr. Kammer has financial interests with Allergan and Merck (Whitehouse Station, N.J.).

Contact information

Radcliffe: drradcliffe@gmail.com
Kammer: jeffrey.kammer@vanderbilt.edu

Toric IOLs possible in glaucoma cases Toric IOLs possible in glaucoma cases
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