Visual outcomes of cataract surgery in glaucomatous eyes hinge on IOL choice

As surgeons embrace cataract surgery as the go-to treatment for select patients with controlled glaucoma, IOL selection plays a vital role in optimizing visual outcomes and minimizing complications.

Clinicians walk a tightrope, balancing quality of vision, IOP and pre-existing ocular pathology, when treating patients for cataracts and glaucoma. Patient age and long-term visual prognosis also factor into the choice of lenses, if any, these patients receive.

In choosing an appropriate lens, a surgeon must consider various features that affect visual outcomes, such as visual field loss, contrast sensitivity and presbyopia. The surgeon must also weigh implantation and lens fixation techniques that may spur glaucomatous complications.

For patients with glaucoma who undergo cataract surgery, long-term outcomes rely on thorough preoperative assessment, Y. Ralph Chu, MD, said.

“The first consideration in eyes with glaucoma is assessing the general overall health of the eye,” Dr. Chu said. “Anybody who gets a premium lens has to have a healthy eye in the present but also maintain that health for a relatively good time into the future.”

Cataract surgery may be the ideal treatment for patients with angle-closure glaucoma, according to Steven D. Vold, MD, shown above. Image: Matt Poe, COA

Ten to 15 years ago, the primary emphasis regarding IOL options for patients with glaucoma centered on concerns about biocompatibility. Now, it is all about visual quality and optics, Thomas W. Samuelson, MD, OSN Glaucoma Section Editor, said.

Multifocal IOLs are suitable for patients with mild glaucoma, but standard monofocal aspheric IOLs are more commonly used. Likewise, for patients with moderate to severe glaucoma, the most commonly prescribed implant is the standard monofocal aspheric IOL, according to Dr. Samuelson.

“When you start looking at optics and visual quality, the most notable improvement in recent years has been the concept of asphericity and improvements in contrast sensitivity,” Dr. Samuelson said.

Aspheric IOLs have gained prominence because asphericity is effective in correcting spherical aberrations. Contrast sensitivity with monofocal aspheric IOLs is superior to that of multifocal IOLs. As a result, the use of multifocal lenses may be relatively contraindicated for patients with significant visual field loss and attendant loss of contrast sensitivity.

“In the 1990s, biocompatibility was the main issue with the evolving foldable technology. Asphericity was the next big step. Now that asphericity has become pretty much the standard, we have other considerations to address, such as presbyopia and astigmatism correction with toric designs. I would say that’s where things get a little bit less clear,” Dr. Samuelson said.

Multifocal IOLs improve near vision, but there is a trade-off, he said. While most patients with normal vision can tolerate that trade-off, those with field loss may not. Accommodating IOLs have less halo effect, but near vision is less than with multifocal designs.

Temporary IOP reduction

Phacoemulsification alone benefits many glaucoma patients, Richard A. Lewis, MD, said.

Richard A. Lewis

“Cataract surgery is an excellent approach to glaucoma,” Dr. Lewis, an OSN Glaucoma Section Board Member, said. “Not only do people see better, but also it reduces pressure in a large percentage of patients.”

By changing the morphology of the eye and decongesting the anterior chamber, cataract surgery reduces IOP by opening the outflow.

Steven D. Vold, MD, said cataract surgery may be the ideal treatment for patients with angle-closure glaucoma.

“Cataract surgery is often the preferred glaucoma procedure,” Dr. Vold said, particularly in angle-closure glaucoma. “Cataract surgery is such an effective procedure. We probably have a 99% success rate in improving patient vision. [The patients] see better, get improved IOP outcomes and, depending on which lens is chosen, can potentially reduce their dependence on glasses postoperatively.”

For example, the aspheric AcrySof IQ ReSTOR IOL with a +3 D addition (Alcon) benefits patients with ocular hypertension or controlled glaucoma and no appreciable visual field loss. The Crystalens accommodating IOL (Bausch + Lomb) is beneficial for patients with suspected glaucoma, ocular hypertension or mild glaucoma. The Tecnis multifocal IOL (Abbott Medical Optics) is suited for glaucoma suspects and early glaucoma, he said.

Dr. Vold said that the IOP-lowering effect of cataract surgery is most significant in patients with higher baseline IOP.

“If they have higher pressures and early to no damage of the optic nerve, cataract surgery is a fantastic treatment,” Dr. Vold said, adding that patients with moderate to advanced disease can also sometimes achieve outstanding outcomes.

However, cataract surgery typically offers only a short-term reduction in IOP, typically 6 to 12 months, Dr. Chu said.

“The cataract surgery will reduce the pressure temporarily, and we can watch it after surgery, depending on how severe the glaucoma is,” he said. However, if the pressure starts to rise, then other interventions may be needed to control the pressure.

Y. Ralph Chu

IOP control can reduce the risk of disease progression but does not reverse existing optic nerve damage or visual field loss, Dr. Samuelson said.

“Phaco is a favorable event in the life of a glaucoma patient,” he said. “It does make pressure easier to control in the majority of patients. But we do not want to confuse pressure control and visual function, which is the primary issue relative to IOL selection.”

Concerns about contrast sensitivity

Patients with early glaucoma and controlled ocular hypertension who do not have appreciable visual field loss may benefit from multifocal IOLs. However, multifocal lenses diminish contrast sensitivity and may not be appropriate for some glaucoma patients, Dr. Vold said.

“Instead of enhancing [the patient’s] vision, you potentially could give them a lesser quality of vision,” Dr. Vold said. “They have paid more but actually receive less. That is the downside of using these lenses.”

Dr. Vold uses the AcrySof ReSTOR multifocal IOL with a 3 D add in patients with stable, well-controlled glaucoma and no significant visual field defects who are less at risk for more progressive loss.

Conversely, significant visual field loss offsets improvements in visual quality offered by multifocal IOLs, Dr. Vold said. Even in moderate glaucoma, he worries about development of advanced disease, he said.

Dr. Samuelson is also cautious when considering multifocal IOLs in glaucomatous eyes with significant visual field loss.

“I am reluctant to use the currently available multifocal implants in the setting of moderate or worse glaucoma,” Dr. Samuelson said. “That is not to say that select patients could not do well with them, but it is hard to predict which ones will. In general, I tend to err on the side of conservatism in that situation. I do use them a fair amount in patients with otherwise normal eyes.”

Thomas W. Samuelson

Implantation of multifocal IOLs is particularly problematic in patients who are dissatisfied with their vision after surgery, Dr. Samuelson said.

“The more confounding variables you have, the harder it is to sort out what is bothering them,” he said. “For example, if a patient with moderate visual field defects complains of the quality of their vision after a multifocal implant, you really do not know what the source of their trouble is. Is it the glaucoma? Is it the multifocality? Is it a combination of the two?”

Accommodating IOLs

Patient selection is critical in cases involving presbyopia correction, Dr. Samuelson said.

“I tend not to use presbyopia-correcting implants in patients with significant visual field loss,” he said. “Patients in whom the glaucoma is moderately advanced or worse, it would be very uncommon for me to use a presbyopia-correcting implant, at least the multifocals.”

However, accommodating IOLs can improve vision in eyes with controlled glaucoma, Dr. Samuelson said.

“The accommodating design is a little more forgiving than the multifocal designs, so I might consider the accommodating type design in patients with moderate glaucoma,” he said.

However, while preserving contrast sensitivity, current accommodating IOL designs often yield less near vision than multifocal lenses. Dr. Samuelson said current multifocal designs split light into distance and near, resulting in better near vision but also potentially reducing contrast sensitivity.

“[Accommodating lenses] more uniformly maintain all the visual input without splitting [light] and just shift the focus. Unfortunately, in my experience, they do not give as much near vision as the multifocals. But I do think that the accommodating designs, as we perfect them more and allow better near vision, hold a lot of promise.”

The Crystalens aspheric optic accommodating IOL, the only accommodating lens currently on the U.S. market, improves vision for patients with mild and moderate glaucoma, Dr. Vold said, but implanting these lenses in severely glaucomatous eyes is counterproductive.

Dr. Vold said that he would not hesitate to use that lens in patients with suspected glaucoma, ocular hypertension or mild glaucoma, but not in advanced glaucoma. “It just does not make sense because you really do not reap the benefits of what the lens can do for you,” he said.

As with accommodating IOLs in general, the Crystalens preserves contrast sensitivity but does not offer near vision comparable to that of multifocal lenses, Dr. Vold said.

“The ideal lens in glaucoma patients, probably, is an accommodative IOL,” he said. “The problem is that it does not give you quite as good near vision unless you do kind of a mini-monovision, where you set a nondominant eye for a little bit intermediate to near, then the distance with the dominant eye. They just don’t have quite the range.”

Improvements in accommodation

An accommodating lens that optimizes near and distance vision would be ideal for all patients, not just those with contrast sensitivity issues, Dr. Samuelson said.

“An implant that uniformly focuses all the light on a single focal point that changes from distance to near would be fantastic,” he said. “That would be the advance that would convert surgeons from using it 5% to 10% of the time to using it in virtually all of their patients.”

The Synchrony dual-optic accommodating IOL (Visiogen) may benefit some glaucoma patients.

“Visually, it may help with pressure reduction because of the accommodation. It could be very useful in glaucoma,” Dr. Lewis said.

The Tetraflex accommodating IOL (Lenstec), currently undergoing U.S. Food and Drug Administration review, offers up to 2 D of accommodation and is a potentially reasonable lens to use in glaucoma patients, Dr. Vold said.

Toric IOLs show promise

The ReSTOR toric multifocal IOL, which is also under review by the FDA, may signify an advance in IOL technology, Dr. Vold said.

“That is going to be a significant advance forward,” he said. “I would not be surprised if that becomes one of the real leaders of the pack of the presbyopic intraocular lenses.”

Toric IOLs are a “win-win” for most glaucoma patients and may be underused, Dr. Vold said.

They are particularly suited to glaucoma patients who undergo cataract surgery after filtration or tube shunt surgery. Toric IOLs are also appropriate for glaucoma patients who have combined cataract surgery and minimally invasive glaucoma procedures such as the Trabectome (NeoMedix), canaloplasty (iScience Interventional), or insertion of the iStent (Glaukos) or CyPass (Transcend Medical).

“Toric IOLs are beneficial to glaucoma patients with astigmatism undergoing cataract surgery alone,” Dr. Vold said. “My impression is that toric IOLs are underutilized in each of these situations by many surgeons.”

Toric IOLs are good for glaucoma patients because they do not diminish contrast sensitivity, Dr. Samuelson said.

“The toric really has very little downside because it is not splitting light and it is not reducing contrast sensitivity,” Dr. Samuelson said. “I am certainly very excited about the implant designs that have recently become available and that we expect to become available.”

Toric IOLs are also ideal for glaucoma patients because they correct induced astigmatism associated with glaucoma surgery. Astigmatism is a common sequela of glaucoma surgery, but once the astigmatism is stable, “correcting that with a toric is great,” Dr. Lewis said.

Phakic and aphakic IOLs

Current aphakic IOL designs are generally not suitable for most glaucoma patients, and they can generate secondary glaucoma.

“One of them sits in the angle and the other one sits behind the iris and causes secondary glaucoma problems,” Dr. Lewis said. “I have real concerns. Alcon is about to release their phakic IOL. It remains to be determined how safe that will be for glaucoma patients.”

Dr. Lewis said that he would be hesitant to use any aphakic IOL, particularly because an iridotomy is done with these lenses and there is some risk for glaucoma development.

“If you have somebody who is either predisposed to or has glaucoma, there is a risk of potentially making their glaucoma worse,” Dr. Lewis said.

The three aphakic IOL designs are anterior chamber lenses, sutured posterior chamber lenses and the Verisyse-Artisan anterior chamber IOL (Abbott Medical Optics), which has an iris-claw fixation design and requires an FDA compassionate use exemption.

“I know that you get outstanding vision with the Verisyse-Artisan IOL,” Dr. Vold said. “You do not have the risk of losing the lens posteriorly, for instance, with loose sutures. It would be a great thing to have available for our aphakic patients.”

Dr. Chu said he is reluctant to implant phakic IOLs in glaucomatous eyes based on anatomic considerations.

“If you are putting a prosthetic in the eye, there is a risk with posterior chamber lenses of pupillary block, pigment dispersion,” Dr. Chu said. “The ocular anatomy assessment is critical. Right now, even in the anterior chamber, whether it is an iris fix, especially an angle fix, you have got to be careful in patients with glaucoma.”

Relatively young patients with pre-existing glaucoma or other ocular conditions are not good candidates for phakic IOL implantation, Dr. Chu said.

“Phakic IOL patients in my practice are usually in their 30s,” he said. “If they are having signs of glaucoma or ocular health issues in their 30s, they have a long way to go with their eyes, so I’m very reluctant to offer any sort of phakic IOL technology in that situation.” – by Matt Hasson

How can emerging developments in IOL materials, designs and optics optimize treatment options available to patients with glaucoma and cataracts?

• Y. Ralph Chu, MD, can be reached at Chu Vision Institute, 9117 Lyndale Ave. South, Bloomington, MN 55420; 952-835-0965; fax: 952-835-1092; e-mail: yrchu@chuvision.com. Dr. Chu is a consultant to Abbott Medical Optics and Bausch + Lomb.
• Richard A. Lewis, MD, can be reached at 1515 River Park Drive, Sacramento, CA 95815; 916-649-1515; fax: 916-649-1516; e-mail: rlewiseyemd@yahoo.com. Dr. Lewis is an investigator for the Visiogen clinical trial.
• Thomas W. Samuelson, MD, can be reached at Minnesota Eye Consultants, 701 E. 24th St., Suite 100, Minneapolis, MN 55404; 612-813-3628; fax: 612-813-3656; e-mail: twsamuelson@mneye.com. Dr. Samuelson is a consultant for Alcon, Allergan, Abbott Medical Optics, AqueSys, Endo Optiks, Glaukos, iScience, Ivantis, Pfizer, QLT and Santen.
• Steven D. Vold, MD, can be reached at Boozman-Hof Regional Eye Clinic, 3737 West Walnut, Rogers, AR 72756; 479-246-1700; e-mail: svold@cox.net. Dr. Vold is a consultant for Alcon, NeoMedix, iScience Interventional, Glaukos and Transcend Medical.