September 2011

 

CATARACT

 

Point, counterpoint on glistenings


by Matt Young EyeWorld Contributing Editor
     

Opinions are varied and so is the evidence, but here's a comprehensive look

At the slit lamp, glistenings look devastating. But ophthalmologists have very different views on the clinical impact of these tiny fluid-filled IOL vacuoles. Glistenings occur in many IOL types, although in some more frequently than others. Most patientseven with severe glisteningsnever complain of them. And yet some ophthalmologists suggest they do matter, especially for younger, refractive lens exchange patients who may be more prone to develop symptoms over time because the severity of glistenings tends to increase over time. When it comes to the significance of glistenings, the reality is that there are many points and counterpoints. EyeWorld explores several here to give some broad, current perspectives on this issue.

Point: Glistenings are here to stay

George H.H. Beiko, M.D., assistant clinical professor, ophthalmology, McMaster University, St. Catharines, Ontario, is convinced that glistenings are detrimental. "I'm of the opinion that this is not a good thing," said Dr. Beiko, medical director of the International Society for Intraocular Lens Safety. The purpose of the society's website, IOLsafety.com, is to "encourage exchange of information to determine if glistenings are innocuous or a detriment to visual quality," but it also sides with the notion that there is "mounting evidence that these glistenings cause vision problems."

"Presence of glistenings in IOL material indicates an inferior product for patients, and it does have an impact on their vision," Dr. Beiko said. "The data that is being presented suggests that glistenings occur in all patients to some degree. The process is ongoing; the longer an IOL stays in the eye, the more intense glistenings become. This is significant because we're dealing with younger patients now." Dr. Beiko drew attention to certain studies on the IOLsafety.com website, which cites both peer reviewed and non-peer reviewed material. What surfaces is the importance of light scatter, a result of eye media such as the lens because of lack of 100% optical clarity.

"This light scattering reduces the contrast of the image projected on the retina, thus decreasing the quality of vision," the website noted, and glistenings may exacerbate scatter even while visual acuity remains unaffected. A PowerPoint by Dr. Beiko on the website, citing research by optical physicist Tom Van den Berg, reported that "lenses with glistenings can cause scatter greater than that present in a 70-year-old's crystalline lens."

Counterpoint: Ugly at the slit lampthat's it

Glistenings have been studied thoroughly and the result is this: There has never been any clinical evidence that they cause clinical problems other than when ophthalmologists look at them and see them at the slit lamp, said Stephen S. Lane, M.D., clinical professor of ophthalmology, University of Minnesota, Minneapolis.

No problems mean no hindrance of visual acuity, contrast sensitivity, color vision, or anything else, Dr. Lane said. "Obviously as clinicians and surgeons, we would prefer to have an absolutely clear optical medium to put in the eye," Dr. Lane said. "The glistenings become more of a cosmetic blemish [for the surgeon's optical view] than anything else."

More glistenings are seen in acrylic materials than silicone ones, although the phenomenon does occur in both, Dr. Lane said. "How can you have all these spots and it doesn't matter?" Dr. Lane said. "I don't have an answer from an optical standpoint because I'm not an optical scientist, but that's the only conclusion we can draw from studies that have been done to look at that variable."

Dr. Lane has a point. A report in Acta Ophthalmologica by Eva Mnestam, M.D., Ph.D., published online in January 2010, studied the impact on visual function from light scattering and glistenings in IOLs implanted 10 years previously. An AcrySof model IOL (Alcon, Fort Worth, Texas) was studied. The result: "Most patients in this case series operated 10years previously had severe glistenings and a high level of light scattering from their intraocular lenses. No detectable impact on BCVA, LCVA [low contrast visual acuity] 10% and 2.5% was found."

Point: Still a visual safety issue

Mark Packer, M.D., clinical associate professor of ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, believes glistenings are a critical issue in ophthalmology because they do exist and especially so in the "huge number of AcrySof lenses" that are implanted in the marketplace. The AcrySof is a leading lens model, and ophthalmologists acknowledge that glistenings commonly happen in these types of lensesregardless of clinical significance. "I'm concerned that we may see more cases of problems with vision with the ReSTOR [the multifocal AcrySof lens] in the future," Dr. Packer said. That said, Dr. Packer has never had to explant an AcrySof IOL due to glistenings, although he cited other such reports. "Every year [patients get older], I see them having more glistenings," Dr. Packer said. "It's almost like a sign of aging."

Although it makes him think twice about implanting AcrySof lensesespecially in younger patientshe acknowledged that there is mixed evidence in the literature on the significance of glistenings.

Counterpoint: A distracting issue

James A. Davison, M.D., Wolfe Eye Clinic, Marshalltown, Iowa, said glistenings are indeed "ubiquitous in hydrophobic plastic." AcrySof IOL material is hydrophobic. "It seems not to bother anything," he added. Certain patient populations have more glistenings than others, such as "people who have more have protein imbalance tendencies in the anterior chamber, like people with diabetes," Dr. Davison said. Even so, those patient groups do not suffer from deteriorated vision, he said. "It's a cosmetic issue from the practitioner point of view," Dr. Davison said, referring to glistening visibility at the slit lamp. "I've never seen anyone have any problems. I've never had to explant a lens or had any complaints." In fact, Dr. Davison believes glisteningsbecause of their visibility at the slit lampare a distracting issue from many other significant ones that ophthalmologists face. They seem like they should make a visual difference but they don't, and ophthalmologists therefore think about glistenings when they should be thinking about other visual problems patients face. What ophthalmology history books will ultimately say about glistenings is unknown. But today, your patients are affected by glisteningsor they aren't. Make your informed decision about whether glistenings make a significant impact on vision, and then let your patient care reflect it.

Editors' note: Dr. Beiko has financial interests with Abbott Medical Optics (AMO, Santa Ana, Calif.). Dr. Davison has financial interests with Alcon. Dr. Lane has financial interests with AMO, Alcon, and Bausch & Lomb (Rochester, N.Y.). Dr. Packer has financial interests with AMO, Bausch & Lomb, and Rayner (East Sussex, England).

Contact information

Beiko: 905-687-8322, georgebeiko@hotmail.com
Davison: 800-542-7956, jdavison@wolfeclinic.com
Lane: 651-275-3000, sslane@associatedeyecare.com
Packer: 541-687-2110, mpacker@finemd.com

Point, counterpoint on glistenings Point, counterpoint on glistenings
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