Multifocal lenses may be inadvisable option for glaucoma patients

For a number of reasons, multifocal lenses are likely to have a negative effect on quality of vision in these patients, surgeon says.

Carole Burillon

PARIS — Multifocal lenses are not an advisable option in glaucoma patients, according to one surgeon speaking at the French Society of Ophthalmology meeting.

“This topic is extremely interesting because chronic primary open-angle glaucoma is a frequent pathology and cataract surgery a frequent procedure in elderly patients. In addition, filtration surgery and cataract surgery are often performed together,” Carole Burillon, MD, said.

“On the other hand, premium lenses are becoming increasingly popular, and many glaucoma patients who undergo cataract surgery now ask for this kind of implants,” Dr. Burillon said.

Halos and reduced contrast

Monofocal implants have a continuous, uniform optic surface that directs light rays toward a single focal point in the retina. Multifocal lenses, however, distribute the incoming light to multiple refractive points, for near, intermediate and distance vision, Dr. Burillon said.

Refractive models, such as the ReZoom (Abbott Medical Optics), have optical zones that alternate near and distance vision through different, dedicated optical zones. They are pupil-dependent, so the amount of incoming light energy varies considerably according to the number of optical zones that are exposed by the diameter of the pupil, and this contributes to halo formation at night time.

Diffractive lenses, such as the Tecnis (AMO), are less pupil-dependent. They direct the light at the same time toward the two near and distance foci. However, each of these two optical zones uses 41% of the light, and the remaining 18% light rays are redirected to higher refractive orders, which generate halos, she said.

Apodized optics, such as the AcrySof ReSTOR (Alcon), integrate the two technologies and reduce photic phenomena because of a more gradual transition to the two points of focus.

“All multifocal lenses, however, perform better in bright light, and a low light may create problems,” Dr. Burillon said.

Apart from photic phenomena, a major drawback of multifocality is that the distribution of light to several refractive points results in loss of contrast.

“This can indeed be a problem in glaucoma patients, who already suffer of reduced contrast sensitivity,” she said.

A reduction of contrast sensitivity is found in 30% of glaucoma patients with no visual field changes, in 60% of normal tension glaucoma patients, who are often diagnosed when the disease is already at a fairly advanced stage, and in 93% of the patients with visual field defects.

“We might end up exacerbating this problem and creating a further handicap in these patients,” Dr. Burillon said.

‘Principle of caution’

The amount of filtration, the presence of a drainage implant, a noncentered pupil, the anatomical changes of the anterior chamber and, potentially, the astigmatism induced by cataract surgery could alter the performance of the multifocal IOL in an unpredictable way. Biometric calculation, which is so important in the outcomes of multifocals, is likely to be imprecise and misleading, Dr. Burillon said.

No negative impact seems to be produced by these lenses on the performance of routine follow-up examinations, such as ocular fundus, optical coherence tomography and GDx (Carl Zeiss Meditec), which are crucial for monitoring the progression of the disease.

“Are multifocal lenses a good option in glaucoma patients? No, for the principle of caution,” she said.

Multifocal lenses should be avoided in patients younger than 60 years, particularly when contrast sensitivity is already reduced by the disease and when visual field is already altered. They should not be used in patients who have already undergone filtration surgery, and also in view of a possible filtration surgery, to avoid refractive surprises. They should not be implanted when combined filtration and cataract surgery are performed because of the potential mistakes with biometric calculation and the induced astigmatism that would jeopardize their performance, Dr. Burillon said.

They can be considered only in a few cases of early, nonprogressive, well-stabilized glaucoma in elderly patients with no signs of macular degeneration.

“Accommodative lenses, which have a monofocal optic and don’t alter contrast sensitivity, are probably a more feasible option. However, I would still go for a classic monofocal implant,” she said. – by Michela Cimberle

• Carole Burillon, MD, a professor at the Edouard Herriot University Hospital, can be reached at Hôpital Edouard Herriot, Pavillon C, Place d’Arsonval, 69003 Lyon, France; +33-4-72116217; fax: +33-4-72116238; e-mail: carole.burillon@chu-lyon.fr. Dr. Burillon has no direct financial interest in the products discussed in this article, nor is she a paid consultant for any companies mentioned.

Multifocal implants should be used in glaucoma patients with caution. My view is that they are not entirely contraindicated, as the majority of patients with glaucoma have a mild form of the disease that is well-controlled, and denying them the potential benefit of multifocality is not appropriate. However, in patients with advanced or unstable disease, caution needs to be exercised.

The basic question raised by the author — are multifocal IOLs indicated in a glaucoma patient — is crucial to our clinical practice. Glaucoma with co-existing cataract is a common scenario. The range of available options has tremendously increased with premium IOLs, and patients need to be offered the best feasible opportunities.

There is a lack of high-level evidence in this field, and we need further research. For the time being, decisions have to be individualized to each patient.

– Som Prasad, MS, FRCSEd, FRCOphth, FACS
Wirral University Teaching Hospital, U.K.