Glaucoma brings special considerations

Key Points

Chicago-Improvements in IOL technology have surged recently, leaving surgeons and patients with a wide selection of IOLs from which to choose. Alan Crandall, MD, described specialty IOLs for patients with glaucoma and considerations that should be given to the use of anti-glaucomatous medications with these lenses here at the American Society of Cataract and Refractive Surgery.

Dr. Crandall said that he uses four corrective IOLs in his practice, including a multifocal, apodized diffractive lens (ReSTOR, Alcon Laboratories), a multifocal refractive lens (ReZoom, Advanced Medical Optics [AMO]), an accommodating IOL (crystalens, eyeonics), and a dual-optic accommodating lens (Synchrony, Visiogen). He is an investigator for the latter IOL, he added.

In the previous 3 months, Dr. Crandall said, he had implanted 28 of the apodized diffractive lenses, five of the refractive IOLs, 22 of the accommodating lenses, and four of the dual-optic accommodating IOLs. He is professor and senior vice chairman of ophthalmology and visual sciences, and director of glaucoma and cataract, at the Moran Eye Center, University of Utah, Salt Lake City.

Dr. Crandall said that, with multifocal IOLs, in contrast to bifocal spectacles and contact lenses, the lens construction simultaneously sends light energy distribution for near and distance vision, which can create a problem with edge sharpness. Monofocal IOLs provide good, crisp images, but multifocal lenses provide a degraded image at all times, which can result in a 25% decrease in contrast sensitivity along with night vision complaints of glare and halos, the latter of which occur more frequently with refractive IOLs and higher-power IOLs, he said.

"The role of the visual cortex is a real issue. The visual cortex, over time, will improve edge definition when the patient becomes neuro-adapted over a 12- to 18-month postoperative period. This should be considered when implanting [lenses in] patients with glaucoma," Dr. Crandall said.

The visual cortex reduces out-of-focus aberrations and delivers functional simultaneous vision at distance and near, but this takes time, he added.

Dr. Crandall demonstrated the process of adaptation that can occur after implantation of an IOL; he used a proprietary model (Array, AMO) for demonstration purposes. Early after implantation, the patient can have blurring of vision at night that later can evolve to good vision at about 3 months after lens implantation. By 18 months, the blurring will have decreased even more.

Which lens?

When considering which lens to implant, surgeons need to think about the patient's motivation, age, and personality type, he said.

"One of the biggest problems with all of the available lenses is that there is no reliable test to figure out while implanting the lens how well the patient will neuro-adapt," Dr. Crandall stated.

An exception is the diffractive bifocal IOL; the light energy is weighted to the center of the lens for reading. When the pupil dilates, he said, the image is shifted to the distance.

Two IOLs (Array, ReSTOR) are pupil-dependent, Dr. Crandall said.

"The ophthalmologist must be aware of the anti-glaucoma medications the patient is taking," he added. For example, Dr. Crandall said, brimonidine tartrate ophthalmic solution (Alphagan, Allergan), which keeps the pupil slightly dilated, will change the images at night and during the day, as will pilocarpine.

With IOLs that are weighted toward reading, patients will have difficulties with distance vision, especially at night.

Compromised reading under reduced lighting conditions is a problem with multifocal IOLs, Dr. Crandall said. One IOL (ReZoom), which is an update from a previous model (Array), has five optical zones and improved optics, he added.

Glare also is a clinically relevant problem in patients in whom multifocal lenses are implanted. When IOLs were evaluated for contrast sensitivity and the effect in patients with glaucoma, Dr. Crandall said, one lens (ReSTOR) was found to be relatively close in quality to monofocal IOLs. Under photopic conditions, the monofocal lens is slightly better; under mesopic conditions, these IOLs are similar, he said.

Multifocal lenses are advantageous for patients in regard to improved optical quality from spherical aberrations, according to Dr. Crandall. Spherical aberrations develop in patients in whom regular IOLs are implanted, he said. The aspheric IOLs manufactured by three companies (Alcon, AMO, and Bausch & Lomb) all are designed with a different strategy, but all decrease spherical aberration in all patients, Dr. Crandall said.

Toric IOLs

The outcomes over the long term with toric implants as they affect the cornea are unknown in patients with glaucoma, he said.

"The toric IOL is very stable, but we do not know what will happen to the cornea if glaucoma surgeries are required," Dr. Crandall said. "Aspheric IOLs can be used with patients with glaucoma and there are no associated problems with slight decentration."

He said that he likes to implant the aforementioned accommodating IOL in patients with glaucoma, but he emphasized caution with multifocal IOLs.