MULTIFOCAL IOLS AND GLAUCOMA PATIENTS

Premium IOLs are suitable for patients with glaucomatous disease, but there are certain cases where they can cause problems and multifocal IOLs are probably to be avoided in most glaucoma patients, said Jean-Philippe Nordmann MD, Hôpital des Quinze-Vingts, Paris, France, at the XXIX Congress of the ESCRS.

Advances in cataract surgery and IOL design mean that emmetropia is routinely achieved for cataract patients who are without ocular co-morbidities. Aspheric and toric IOLs can further enhance cataract patients’ vision and newer multifocals can provide complete spectacle independence in the majority of cases, he said.

However, a different situation prevails in patients with glaucoma or ocular hypertension. In cases of combined surgery phaco and trab, it is not always possible to evaluate preoperatively the post-op astigmatism. The relative loss of vision with multifocal IOLs may actually increase the perception of glaucomatous visual impairment, Dr Nordmann pointed out.

“Glaucoma involves some specific types of structural and functional impairment. For example, glaucoma patients can have significant reduction in contrast sensitivity, correlated with visual field changes, especially in advanced cases. We know well now that when choosing a lens the contrast sensitivity achieved is very important.â€

Surgical challenges

Glaucomatous disease can make cataract surgery more complicated in several ways, Dr Nordmann said. For example, in some cases, especially in angle closure glaucoma, there will be poor pupillary dilatation and bad quality pupillary function. That is particularly true in patients who have received pilocarpine for an extended period and those who have undergone laser iridotomy, he noted.

In pseudoexfoliative and in traumatic glaucoma, the zonule is often fragile which necessitates special care during surgery and limits the choice of IOL, he said. In addition, anterior chamber depth and axial length may be reduced after filtration surgery or combined surgery. Those changes require consideration when calculating IOL power, especially in patients with high myopia, in young patients, and in patients with very high preoperative IOP as it is the case with angle closure glaucoma. “The choice of the implant in such cases should probably target a slight myopia of half a dioptre to one dioptre in order to reach a normal value due to this reduction of the size of the eye after filtration surgery,†Dr Nordmann said.

Aspheric lenses are designed to improve contrast sensitivity especially under mesopic and scotopic conditions by compensating for the positive spherical aberration of the cornea. They can be of benefit to glaucoma patients who may have reduced contrast sensitivity. However, the vision enhancing effect of most aspheric lenses is dependent on good centration. Aspheric lenses are contraindicated in patients at risk of poor centration, such as eyes damaged by trauma, where they cause distortions of vision.

Multifocal lenses are a good option for some patients because they can eliminate the need for spectacles for near or distance vision. However, since they work by dividing the light between two different focal points, they reduce the contrast of both images.In glaucoma patients they can add to any reduction in contrast sensitivity that is present or will occur in the future as the disease progresses. Multifocal IOLs can make the monitoring of patients’ glaucoma difficult because they can produce OCT artefacts.

Toric IOLs can be an option in many astigmatic glaucoma patients, but should be avoided in some patients with advanced pseudoexfoliative glaucoma because of their zonular instability. Nor should they be used in eyes undergoing a combined phacoemulsification and trabeculectomy procedure, because astigmatism following such operations is unpredictable, he said.

Taking some of the main types of glaucomatous disease individually, Dr Nordmann said that patients with very stable ocular hypertension are suitable for all the same types of IOLs available to cataract patients without co-morbidities. The same is true for patients with early glaucoma that has been stable for a long time, he added.

However, in patients with moderate or advanced glaucoma, multifocal IOLs should be avoided, he stressed. He added that a surgeon often has no way of knowing whether a patient’s glaucoma is truly stable or will progress in the future.

contact Jean-Philippe Nordmann – j.p.nordmann@quinze-vingts.fr