The Impact of IOLs on Posterior Segment Care

Design and material can be just as important to retina surgeons as they are to cataract surgeons.

BY RICHARD JOSEPH HAIRSTON, MD

Given the average age of the patients typically seen by retina specialists, it's no surprise that the majority of them, close to 80% in my experience, are pseudophakic. As these patients reach their 70s and beyond, it's likely they'll require more frequent evaluations and perhaps treatments or surgeries by a retina specialist. When that time arrives, it's important that the IOL not interfere. A clear IOL optic is crucial for useful clinical examinations, preoperative evaluations and successful in-office laser procedures. An obstructed view of posterior segment structures can be particularly detrimental to the accuracy and effectiveness of surgical procedures. Problems with visualization and other issues can arise with just about any IOL in use today, depending on the design and material.

For example, although PMMA lenses are rarely used, many of our older patients had them implanted years ago. Most PMMA IOLs have a three-piece design, which can present short- and long-term problems with centration. Three-piece lenses also can be difficult to manage should the lens become dislocated posteriorly. The same can be said for plate lenses. Unlike one-piece lenses with loop haptics, plate lenses can only be grasped in one plane, making it difficult to manipulate in the event of a dislocation. Plate lenses also can inhibit the posterior segment surgeon's view of the retinal periphery, especially if some peripheral opacification of the capsule is present. Lenses with small optics, too, can inhibit the view in the periphery.

Even today's most advanced IOLs, such as multifocals, may have drawbacks from a retina surgeon's perspective. As a general rule, cataract surgeons avoid implanting multifocals in patients with posterior segment conditions or diseases, but future eye health isn't always predictable. In cases where subsequent retina surgeries are required, the view through a multifocal isn't as crisp when compared with a monofocal. Multifocals with concentric rings of varying refractive power can obstruct the view, making detailed macular work or membrane peeling as difficult as it is through a cataract. Furthermore, the risk of iatrogenic tissue damage is increased when a surgeon experiences changes in depth perception while looking through the different optical zones.

Glistenings in an IOL optic of any material can also be a source of difficulty during a posterior segment procedure.

In certain situations, the IOL material may make retina surgery more challenging. Silicone oil is a valuable adjunct for the retina surgeon, especially in complicated detachment cases, but it can't be used in the presence of a silicone IOL. The oil adheres to the silicone material, robbing the lens of its refractive power. In addition, condensation tends to form on silicone IOLs during fluid/gas exchange in eyes that have previously undergone a YAG capsulotomy. This can also occur with PMMA or acrylic lenses, but with silicone, it tends to produce an instantaneous obstruction of view. Glistenings in an IOL optic of any material can also be a source of difficulty during a posterior segment procedure. Although they haven't been a common problem for me, the risk that they could become an issue is certainly not ideal. Like anything with the potential to distract from a safe, efficient procedure, glistenings are something posterior segment surgeons would rather avoid.

A Retina Surgery-Friendly IOL

Fortunately, one of the newest IOLs available to our anterior segment colleagues is also retina and retina surgery-friendly. The enVista IOL (Bausch + Lomb) is made from a UV-absorbing hydrophobic acrylic, a material type many cataract surgeons prefer. Because acrylics tend to be durable and well tolerated in the eye, they're a solid choice for patients with diabetes and inflammatory conditions. Also, during vitrectomy, if the IOL is acrylic, the surgeon can use any tamponade — gas or silicone oil for example — without worrying about its effect on the lens. The enVista acrylic material offers an additional benefit in being clear and glistening-free. The lens' labeling reflects this, as does surgeon experience more than a year after the lens was introduced.

In my experience, the enVista IOL hasn't been the source of any problems during posterior segment evaluation or treatment in the clinic or OR. These implants have a relatively large, aberration-free aspheric optic and they've been clear and well-centered, all of which enhances my view.

Further augmenting the enVista's value to retina surgeons and their patients are its PCO-minimizing features. Lens epithelial cell migration is inhibited by the 360-degree square edge, and the haptics are designed to vault the optic posteriorly for direct contact with the capsular bag. Reducing the rate of PCO among vitreoretinal patients is important for a variety of reasons. The ability to avoid a YAG capsulotomy helps to reduce the rate of future retinal tears and detachments, and spares eyes with inflammatory conditions the inflammation induced by a YAG capsulotomy. Also, with an intact capsule, condensation doesn't form on the IOL during fluid/gas exchange, and the chance of silicone oil migrating to the anterior chamber is virtually zero. Finally, the absence of capsule opacification almost guarantees the retina surgeon will have a clear view. This is important because even opacification that's not extensive enough to warrant a YAG procedure can be problematic.

Because implantation of the enVista IOL is straightforward, it works well for combined cataract and retina surgery. The cataract surgeon can implant the lens through a small incision and is unlikely to be faced with an extended operating time. In turn, corneal edema is minimized and less likely to interfere with the posterior segment surgeon's view.

Setting the Stage for Success

The diagnosis and management of vitreoretinal conditions require an unobstructed view to the back of the eye, and the safety and effectiveness of today's delicate surgical interventions depend on clear visualization of the macula and periphery. Ideally, retina specialists are examining and treating patients who have opacity-free capsules and well-centered, well-tolerated IOLs with clear optics. Under these conditions, we can focus on the task at hand unencumbered and perform procedures efficiently, which is in the best interest of our patients. The easier I can do what I need to do and get out of the eye, the better I feel. The enVista IOL has been noticeably crystal clear and stable and thus helpful in making that happen.●

Dr. Hairston is co-director of the Retina Center at the Eye Institute of West Florida, a longtime leader in Tampa Bay area eye surgery.