Since 1949, when British surgeon Harold Ridley implanted the first intraocular lens (IOL), cataract patients have experienced gradual progress toward fully restored vision. Today, IOLs with a higher refractive index are correcting visual error so well, many post-cataract patients have better vision without glasses than they enjoyed for much of their adult lives. New materials allow for easier insertion of IOLs, and improved biocompatibility is even reducing the incidence of posterior capsular opacification (PCO) and the concurrent need for YAG laser capsulotomy.

"In the past few years, we've had a push toward foldable IOLs that we can place through a clear corneal incision, allowing us to use a topical anesthetic. Better design and better surgical technique are reducing the incidence of PCO from as high as 35 to 50 percent of cases, to less than 10 percent," notes Nick Mamalis, MD, Professor of Ophthalmology at Moran Eye Center, University of Utah.

What may be the biggest problem for surgeons is the sheer variety of choices in IOLs. In addition to polymethylmethacrylate (PMMA), the plexiglass first implanted by Dr. Ridley, there are three categories of lens materials. Within each category are various brands and designs, each of which seems to do something better than other products. Surgeons say they sort out the claims by focusing on what's most important.

"For the ophthalmologist, there are two things that are most important in an implant. The first is how it performs clinically for the patient. The second is how user-friendly it is. I'm talking about handling for the nurses, and ease of insertion: Is it a nightmare in the OR?" says Richard Tipperman, MD, of Wills Eye Hospital in Philadelphia, Pa.

The newer materials and designs all are more expensive than PMMA and are significantly higher in price than first-generation silicone IOLs. Yet some surgeons who have tried them say the benefits to patients make them well worth it.

"This is the implant I want in my eye," says Warren E. Hill, MD, of Mesa, Ariz., regarding the new Acrysof one-piece IOL. "There are no real limitations with this IOL."

Following is a review of some of the newer IOLs, divided by material.

Silicone
This lens material has been in use for years, but we're now looking at second- and third-generation products. The new silicone lenses offer a higher refractive index, which means the lens can correct higher amounts of visual error without added bulk. These lenses also are more biocompatible, causing less PCO than PMMA implants.

ClariFlex with OptiEdge from Allergan is a third-generation IOL just launched this year. It offers a rounded edge that reduces internal reflections or glare. A rounded anterior edge scatters light, while the sloping side edge directs reflections away from the retina. A square posterior edge provides stability. Allergan's injection system implants the IOL through a 3-mm incision, and the folded IOL slowly unfolds in the eye. Another benefit of the injection system is that it prevents IOL contact with the wound and exterior of the eye, reducing the potential for postoperative inflammation.

CeeOn EDGE 911 and 913 were introduced by Pharmacia last April and October, respectively. Called "next-generation" silicone lenses, these IOLs have a higher refractive index, which is closer to that of the natural lens. Studies show that they diminish glare, and a special posterior edge diminishes the incidence of PCO.1 YAG capsulotomy rates for CeeOn are a low 3.5 percent.

A recent study of 180 eyes compared six IOLs (two versions of CeeOn, Hydroview, Acrysof, Sensar and MemoryLens).2 Results showed the incidence of PCO was lowest for CeeOn, particularly the 911, with its "sharp edge design." Patients who received CeeOn had a "good uveal and capsular biocompatibility one year after surgery." At this time, an injection system for CeeOn is in development.

PhacoFlex II from Allergan is the second generation of the PhacoFlex IOL. Allergan asserts that three studies show that this implant provides 20/20 vision for 96 percent of patients, and 20/40 vision for all patients. The company offers the same injectible implantation as with Clariflex.

Array from Allergan is a multifocal IOL that gets mixed reviews from surgeons, who, along with patients, love the idea of a visual correction for near and distance. But some surgeons say Array's performance is not consistent.

"It's hard to tell who the Array is going to work for. It does allow people to see up close and far away, but the explantation rate is high. I would rather do a moderate undercorrection in one eye. I call it ?monovision light'," says Dr. Horn.

Other surgeons have had better success with this IOL. "The Array has tremendous advantages for the interested or motivated patient. Distance vision is strong [with the Array] and the near vision continues to improve over time as neuroadaptation occurs. The disadvantage is the haloes and glare?these are tolerable and diminish as time passes," notes Avery D. Alexander, MD.

Staar Toric IOL attempts to correct another common visual problem-preexisting astigmatism. This lens is injectable through a small incision. In published reports, Staar surgical states that even in clinical studies, it provided uncorrected visual acuity of 20/30 or better for just 47 percent of patients.3 To get it to work right, surgeons must place the IOL very precisely and avoid rotating it away from its desired axis.

"If you have just a bit of unintended rotation, you can actually add astigmatism. It has a 10 percent explantation rate. What we need is a toric IOL in a one-piece acrylic design," says Dr. Horn.

Phakic IOLs May Offer Refractive Entry Point Cataract surgeons and facilities that serve them are likely to encounter an intriguing entry point to the refractive surgery market. Phakic IOLs for the correction of myopia, hyperopia and astigmatism are in clinical trials in the US and may be released in 2002 and 2003. The most-talked-about products are the Implantable Contact Lens from Staar Surgical (ICL) and the Artisan Phakic IOL from Ophtec. An important target market for phakic IOLs are patients with high myopia and others contraindicated for laser procedures such as LASIK and PRK. Both of these implants have been available in Europe and other foreign markets for years. Surgeons report refractive results that are very good for patients who are not "ideal" candidates for laser procedures. In US clinical trials, both Staar and Ophtec report results in the neighborhood of 90 percent of patients seeing 20/40 or better without glasses or contact lenses. The downside of phakic IOLs is that successful implantation seems to be surgeon sensitive. When the natural lens is intact, and the objective is to keep it intact, there's less room to work, and a smaller margin of error. "In cataract surgery, there's a lot of room to move around, get rid of the lens, and implant the IOL. But here the lens is sacred, rather than an object to be removed. Everything is much more deliberate and slow," says ICL investigator Stephen Bylsma, MD, of Santa Maria, Calif. While both of these phakic IOLs are implanted with the natural lens intact, the ICL is implanted in the posterior chamber and the Artisan is an iris-fixated, anterior chamber lens. Thus, surgeons are faced with differing benefits and challenges. ICL investigators say that selecting the correct size may be the biggest challenge. Staar calculates the size based on A-scan, refractive error and corneal diameter, all supplied by the surgeon. If the ICL that's selected is too small, it may contact the natural lens, causing capsular opacification or lens changes. If it's too large, it can cause shallowing of the anterior chamber. The ICL is foldable, which means it can be inserted through a small, 2.7-mm corneal incision, always a plus from a surgical point of view. The ICL is made of a flexible copolymer containing collagen, which seems to minimize insult to the eye. A posterior chamber IOL is further away from the corneal endothelium, which may reduce the chance of developing long-term endothelial loss. Artisan's material may be its biggest drawback. Made of rigid PMMA, the 5-mm or 6-mm IOLs must be inserted through a large, 6-mm incision, which requires sutures. This inflexible implant could potentially damage the eye if subjected to blunt trauma or chronic eye rubbing, some surgeons say. The 5-mm size Artisan has been associated with patient complaints of glare and haloes. On the other hand, there's no sizing problem with Artisan. Centration and fixation is very good with Artisan, making it a reliable implant once in the eye. At the same time, investigators say it's easy to reposition or replace the Artisan if needed. Because Artisan has been used for 14 years in Europe, the FDA gave Ophtec permission to skip over its Phase II clinical studies for hyperopic patients and go directly to the Phase III studies. Because of the potential size of the market for phakic IOLs, ICL and Artisan are not the only implants on the horizon. Medennium's (Monrovia, Calif.) Phakic Refractive Lens is also in US clinical trials. CIBA Vision holds the worldwide rights to market that product, as well as a tripod-shaped foldable IOL made by a French company.