March 2007

 

CATARACT/ IOL

 

Minding the P’s and Q’s of PCO in multifocal vs. monofocal IOLs


by Maxine Lipner EyeWorld Senior Contributing Editor

 

 

For multifocal patients, early awareness of PCO may be mind over matter

Mixed (cellular and fibrotic PCO) but predominantly cellular PCO.

Mixed (cellular and fibrotic PCO) but predominantly fibrotic PCO.

Cellular PCO.

Source: Mostafa A. Elgohary, M.D.

Fibrotic PCO with wrinkles on the posterior capsule.

Fibrotic PCO with grayish fibrotic deposits on the posterior capsule.

Source: Mostafa A. Elgohary, M.D.

When dealing with lens replacement, posterior capsular opacification (PCO) is an unfortunate fact of life. Recent study results, published in the December 2006 issue of Eye, indicate that complaints about early visual functional loss can happen in patients undergoing multifocal lens implantation more than in monofocal counterparts.

PCO in monofocal lenses has been thoroughly studied over the years, though PCO in multifocal lenses hasn’t received the same attention, according to Mostafa A. Elgohary, M.D., specialist registrar, Moorefields Eye Hospital, London. “There were no studies whatsoever that assessed the effects of PCO on visual function in patients multifocal implants,” said Dr. Elgohary, who decided to launch a study on the subject. “We wanted to find out what the functional effect of PCO was in patients with multifocal implants in comparison to those with monofocal implants,” he said.

Patients who presented with PCO and who needed Neodymium:Yittrium-Aluminum-Garnet laser (Nd:YAG) capsulotomy were recruited for the study. “These patients were either self-referred or referred by their family physician to have a capsulotomy because they developed symptoms that were believed to be related to the development of PCO,” Dr. Elgohary said. “We excluded patients who had concurrent ocular disease that could potentially affect the visual function” leading to a toal of 24 patients with monofocal IOLs and nine with multifocal lenses.

Comparing PCO grades

In the study, investigators looked at the PCO type and grade. If the patient had multiple pearls on the posterior capsule, this was defined as the ‘cellular type’ of PCO; if they had a gray sheen on the capsule without too many pearls, this was dubbed the ‘fibrotic type’. “The majority of patients had a mixture of both,” Dr. Elgohary said. He assessed how dominant their PCO type was based on whether it involved coverage of 50% or more of the area behind the IOL, especially in the central 4 mm of the pupil. PCO was graded mild, moderate, or severe based on the visibility of the details of the retinal structures through the PCO.

When investigators compared presentation timelines between the monofocal and multifocal groups, they determined that the mean follow-up in the monofocal group was 36.5 months compared to just 24.8 months in the multifocal group. Investigators determined that mild PCO occurred in the monofocal group 20.8% of the time versus 55.6% in the multifocal group when they examined the degree of PCO. Moderate PCO was found in 54.2% of monofocal cases versus 33.3% of multifocal patients, and 25% of monofocal cases were severe compared to just 11.1% in the multifocal group, according to Dr. Elgohary. The difference between the two groups was not significant.

There was an effect on all visual function, predominantly on visual acuity. “The monofocal group seemed to have much worse high- and low-contrast visual acuity than the multifocal group, which was statistically significant,” Dr. Elgohary said. “Still, the contrast sensitivity and the at-near visual acuity were slightly worse in the monofocal group, but that wasn’t statistically significant.” The only statistically significant finding was the difference in the high- and low-contrast visual acuity, which was found to be worse in the monofocal group. When the patients were asked about their visual symptoms, investigators found that 95.8% of monofocal patients complained of blurred distance vision versus 88.9% of those in the multifocal group, and 100% of monofocal patients had blurred vision at near compared to 66.7% of those with multifocal lenses.

These results were a surprising. “Initially, we thought that the multifocal group would suffer more, and therefore their visual function would be worse than in the monofocal group,” he said. “However, when we thought about it more, we realized that it actually makes sense [that monofocal patients would have worse results] because the multifocal group seem to be more conscious about their eyesight,” as they opt for multifocal lenses. Also, these patients receive counseling on visual problems related to multifocal IOL (e.g. reduction in contrast sensitivity, glare and haloes), about which they should be concerned. “This makes them more aware of the symptoms, and therefore they tend to present earlier with earlier functional loss than patients in the monofocal group,” Dr. Elgohary said.

While visual loss other than low- and high-contrast acuity was comparable statistically between the two groups, individual numbers tell a different story as at-near vision, contrast sensitivity and color vision were consistently lower in the multifocal group. “The majority of multifocal patients—more than 50%—had mild PCO,” he said. “A smaller number in comparison to the monofocal groups had the severe type—11% versus 25%.” This indicates that most multifocal patients likely present as soon as they become aware of any PCO symptoms and therefore present earlier, he said.

Multifocal implications

Based on the study findings, investigators concluded that patients with multifocal lenses tend to present with earlier visual function loss than patients with monofocal lenses. “The implication is that these patients might have a higher rate of YAG capsulotomy or tend to request the Nd:YAG capsulotomy more,” Dr. Elgohary said.

He urges practitioners to keep this in mind when they implant multifocal IOLs. “Obviously, one should make sure one takes all the measures during and after the operation that would reduce the incidence or the probability of these patients developing PCO,” he said. Dr. Elgohary emphasizes that practitioners limit their capsulorhexis to 5 mm or smaller, make sure they do a meticulous cortical cleanup of the soft matter, put the lens inside the capsular bag and use new IOLs with square-edges; all these measures have been shown in the studies to reduce PCO development. In some cases, polishing the anterior capsular leaflet in order to remove as much of the lens epithelial cells as possible may also be appropriate. “If the patient develops uveitis or inflammation he or she needs to go on a high dose of steroids as quickly and intensely as possible to reduce the inflammatory drive that is believed to increase the rate of PCO,” he said.

Such fastidious measures may help to forestall the need for Nd:YAG capsulotomy in this PCO-vigilant population, he said.

Editors’ note: Dr. Elgohary has no financial interests related to his comments.

Contact Information

Elgohary: 44-793-927-4217, m.elgohary@doctors.org.uk

Minding the P’s and Q’s of PCO in multifocal vs. monofocal IOLs Minding the P’s and Q’s of PCO in multifocal vs. monofocal IOLs
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