Spotlight ON TECHNOLOGY & TECHNIQUE

Snowflakes Should Glisten; IOLs Should Not

By Bill Kekevian, Associate Editor

Glistenings are fluid-filled microvacuoles that can form within an IOL. These “opacities one sees within the optic of certain IOL implants,” as Louis “Skip” Nichamin, MD, calls them, are fairly common. While they may not impart visual degradation in most cases, Dr. Nichamin says he has seen patients reporting problems with visual acuity, which he attributes to severe IOL glistenings.

While some controversy surrounds the impact glistenings can have on patients, surgeons are frustrated by their presence, Dr. Nichamin says. They can be caused by the IOL material composition, the manufacturing technique, packaging flaws, or associated patient factors such as glaucoma or those leading to breakdown of the blood-aqueous barrier, according to a 2010 ASCRS study.

The FDA approved Bausch + Lomb's new enVista IOL in June. The hydrophobic acrylic IOL is designed specifically to eliminate glistenings.

The Trouble With Glistenings

The desire to reduce glistenings certainly has an aesthetic element to it. However, research has suggested patients with IOL glistenings may experience sensitivity due to light scatter.¹

Dr. Nichamin, medical director of Laurel Eye Clinic in Brookville, Pa., was one of the principal investigators in the FDA trials for enVista. He says glistenings are especially problematic for pediatric ophthalmologists. For young patients, IOLs need to last. Implants from the 1990s, Dr. Nichamin says, have shown increased glistenings.

The Studies Are In

In fact, a 2009 study set out to quantify these glistenings.¹ The study showed older IOLs continued to develop glistenings for up to a decade. In a two-year prospective study of 172 eyes, according to B + L, no glistenings were detected in patients implanted with the enVista IOL at any time.² The glistening-free quality of the lens is due to a proprietary, advanced hydrophobic acrylic material hydrated to equilibrium and stored in 0.9% (physiological) saline. This saline eliminates fluid exchange with the aqueous humor.

The hydrophobic acrylic material was examined in a study in the July issue of Journal of Cataract and Refractive Surgery.³ That study aimed to determine the anti-glistening properties of the material. Results showed that, even under the worst conditions, the new material was more stable. It also showed the material resisted the formation of posterior capsule opacification (PCO), a common postoperative complication with IOLs that can cause blurry vision. Also, in the effort to limit PCO, the IOLs are designed with step-vaulted haptics that vault the optic posteriorly for direct contact with the capsular bag.

Ease of Use

While the glistening-free design is the primary selling point for the lens, Dr. Nichamin says the enVista has several other benefits.

For starters, the product is designed to last longer than the average IOL. “It's a very stable lens,” Dr. Nichamin says. He adds that the enVista “handles well” and that European surgeons who have employed the IOL have reported very few complaints.

The IOL is inserted through a 2.2-mm incision with a single-use injector. Controlled unfolding facilitates positioning in the capsular bag and removal of the viscoelastic. The enVista obtained a CE Mark in 2011. OM

REFERENCES

1. Behndig A, Monestam E. Quantifications of glistenings in intraocular lenses using Scheimpflug photography. J Cataract Refract Surg. 2009; 35:14-17
2. van deer Mooren M, et al. Light scatter characteristics of acrylic intraocular lenses. ARVO 2007 Abstract
3. Pagnoulle C, et al. Assessment of new-generation glistening-free hydrophobic acrylic intraocular lens material J Cataract Refract Surg. 2012;38:1271-7.