Sizing up the Refractive Surgery Options

LASIK is still king but specialized procedures abound

BY LESLIE GOLDBERG, ASSOCIATE EDITOR AND JERRY HELZNER, SENIOR EDITOR

Although patient demand for refractive surgery procedures leveled off sharply in the last few years, the pace of innovation did not: surgeons and device manufacturers continued to refine their techniques and technology during the market's fallow period, and assert that they're now better positioned to capitalize once the rebounding economy reinvigorates interest in surgical solutions to refractive error.

Progress has been twofold: while mainstay procedures like LASIK and PRK have been refined to improve outcomes, newer options seek to expand the scope of what refractive procedures can accomplish. “There is definitely an attempt to broaden the patient base with the increasing focus on correcting presbyopia and hyperprolate cornea ablations, but increasing precision and reproducibility with femtosecond lasers is equally an emphasis,” says the Cleveland Clinic's Ronald Krueger, MD, co-director of this year's AAO refractive surgery subspecialty day. Tellingly, the 2009 program's theme is “It's Time to Change.”

Be it a question of procedure preference, patient selection, surgical devices or simply mindset, change is in the air. Which procedures are being updated and which are becoming outdated? What will drive prospective patients who want spectacle independence to take the plunge in this still-unsteady economy? Which procedures have fully evolved, and which still have growing pains ahead? This article will outline the latest thinking on key benefits of each procedure.

LASIK

LASIK remains the most popular and well-known type of refractive surgery by a wide margin. “LASIK is still king,” says Dr. Krueger, “and femtosecond lasers have been crucial in maintaining that status.”

Marguerite McDonald, MD, clinical professor of ophthalmology at NYU and in private practice in Long Island, NY, says that femtosecond technology has allowed surgeons to make customized flaps: oval flaps that are oriented in the proper axis, thinner flaps and smaller flaps, with reverse beveled flap edges for better adhesion. These options all lead to less dry eye while sparing more corneal nerves and decreasing the chance of postop ectasia. “While it's still within the standard of care to use a mechanical microker-atome in 2009,” says Dr. McDonald, “I believe that within the next three to five years virtually all LASIK surgeons will be switching over to femtosecond technology, for its safety, predictability and excellent outcomes.”

Regarding ablation profiles, she says that, until recently, nothing could touch the results achieved with wavefront-guided PRK, but wavefront-guided LASIK with a femtosecond laser has now matched it. “Wavefront-guided PRK and wavefront-guided LASIK with the IntraLase to create the flap are equal in quality of vision — however, LASIK still achieves faster results. Historically, I think it will be seen as a watershed moment in LASIK that we now have access to advanced femtosecond technology,” concludes Dr. McDonald.

“The way to get the refractive surgery market to grow is to give patients something better than corrective lenses, something they've never seen before,” says Eric Donnenfeld, MD, also of Long Island. “20/16 is the new 20/20.” That outcome, he says, is within reach for most patients. In a recent retrospective study of 32,569 eyes treated with the Visx Star S4 laser, he says, 89% achieved 20/16 uncorrected acuity. Dr. Donnenfeld also mentions that 97% of patients rated their postop vision better than preop best-corrected acuity in a prospective study of 200 eyes treated with the triumvirate of femtosecond-created flaps, custom wavefront ablations and a laser that uses iris registration.

LASEK: Similar to PRK — or Superior?

According to the 2009 “US Trends in Refractive Surgery” study, approximately 30% of refractive surgeons are currently either performing LASEK or are interested in adding it to their practice. Those who aren't tend to describe the procedure as “similar” to PRK. However, those surgeons who are LASEK proponents, such as Thomas V. Claringbold, DO, of Clare, Mich., will assert that LASEK has several major advantages over PRK.

Dr. Claringbold, a LASEK pioneer who has trained other surgeons in the procedure, contends that the key to the highly successful outcomes he consistently achieves is the replacement of the epithelial sheet.

“The sheet provides a skin bandage, which produces less glare and less haze, even without the use of mitomycin,” says Dr. Claringbold. “In addition, we have been doing studies with an advanced driving simulator at Central Michigan University and our preliminary data show that LASEK patients demonstrate better driving vision under mesopic conditions than PRK patients. Moreover, patients who have had surface ablations tend to show much better mesopic driving vision than those who had LASIK.”

One issue that has held back the growth of LASEK has been postop pain control. Dr. Claringbold had tried several combinations until about 18 months ago when he began to use Lyrica (Pfizer), which has been widely used for nerve-related leg pain in diabetics. “I had been using Vioxx and Celebrex, which are completely safe for patients to use for five to seven days with ocular surgery,” he says, “but after Vioxx was taken off the market, just the names alone were a little scary to the patients.”

Dr. Claringbold had heard good things about Lyrica from neurologists and other colleagues so he put it into his pain-reduction regimen, starting it 72 hours preoper-atively and continuing it for four days postop. He prescribes a low daily dose of 75 mg at bedtime because the one side effect of Lyrica that he has seen is drowsiness. “It's really helped,” he says. “The feedback from patients has been great. I no longer get the phone calls for the first three or four days postop. I've passed the idea on to other LASEK surgeons and they are experiencing good results with it as well.”

Dr. Claringbold says that a number of surgeons who have adopted LASEK now do it exclusively. “They tell me that their stress level is reduced and their blood pressure is down since abandoning the microkeratome,” he says. “They are actually enjoying performing this surgery.”

Dr. Claringbold believes that LASEK may be best suited to surgeons in smaller practices because the procedure requires more chair time with patients than LASIK. “I do my own refractions,” he notes. “In bigger practices, a lot of the workup is left to techs. For a surgeon who has a hands-on approach, LASEK is the perfect procedure.”

PRK

Despite LASIK's preeminence, PRK remains a viable option and is still preferred by some refractive surgeons. “It is difficult to prove that PRK is better than LASIK or vice-versa but the proponents of the technique hone their skills in it and become advocates of it,” Steven Safran, MD, of Lawrenceville, NJ posted on the discussion board www.asklasikdocs.com.¹ In that post, he mentioned that he prefers PRK over LASIK for the following reasons:

► It is more sparing of corneal tissue and nerves, thus posing less risk of postop ectasia or dry eye.
► The absence of a flap eliminates the risks of striae/microstriae, fine flap irregularities, epithelial ingrowth, flap dislocation and diffuse lamellar keratitis.
► Studies on cadaver eyes with a history of LASIK while alive showed fluid in the interface on all eyes. One concern is fluid collecting there if cataract, retina or glaucoma surgery is needed (or if inflammation, uveitis, other diseases affect the eye), as fluid tends to collect in potential spaces when there is inflammation or edema.
► PRK is less frightening to the patient during surgery (no suction ring, no mechanical contraptions etc.)
► Results are easier to enhance — just do PRK again. “Some of us hate re-lifting flaps because of increased epithelial in-growth risk,” Dr. Safran noted.
► The quality of vision in the long run is better with PRK in Dr. Safrans experience.

He pointed out that the downside of PRK is longer time to heal and to obtain the best quality of vision. “Some people feel there may also be a slightly higher infection rate during the healing period, but if you watch patients closely during this time it is my belief that this risk is very low,” Dr. Safran noted. “Now epi-LASIK with a keratome versus PRK is another argument, but I personally prefer PRK because it's simpler, cheaper, easier, doesn't rely on expensive equipment working just right, is less scary to the patient, has no risk of stromal incursion by the blade, and there is some risk to the suction ring itself and having the pressure elevated in the eye while it is applied that is avoided.”

SBK — Really Just Modern LASIK

“Sub-Bowman's keratomileusis is really modern thin-flap LASIK surgery,” says Daniel Durrie, MD, of Overland Park, Kan. “It's an evolution of LASIK. We are creating the thinnest flap possible with the most modern technology to make it safer by cutting less fibers and nerves.”

SBK creates less postop dry eye than PRK and there is less biomechanical destabilization of the eye compared to previous LASIK procedures, says Dr. Durrie. A prospective study comparing PRK with SBK that he did with Stephen Slade, MD, found that both procedures had excellent results at 3, 6 and 12 months but visual recovery was dramatically faster in SBK patients. Dr. Durrie says you can choose either procedure for an individual patient, as both are safe and effective.

Dr. Durrie says that while some doctors still perform SBK with a microkeratome, most use a femtosecond laser. “While IntraLase is the dominant player in this field, other companies are now creating femtosecond lasers, which endorses the procedure's staying power.”

Dr. McDonald says that using a femtosecond laser for SBK “allows you to deliver a super-thin flap without creating a buttonhole.” She says most surgeons don't program the femtosecond laser for a flap less than 110 microns in thickness because below that level, the flap can wrinkle, there is the remote potential for gas breakthrough (through a shallow corneal scar) and the flap can exhibit less structural integrity. “You get diminishing returns when the flap is too thin,” says Dr. McDonald.

Epi-LASIK was the creation of the inventor of LASIK, Ioannis Pallikaris, MD, of Crete. He felt that there were many advantages to this iteration of surface ablation, advantages that are similar to PRK: it was quite safe, there was not a cut into the stroma, and there was less chance of ectasia, Dr. McDonald explains.

The disadvantages were also similar to PRK: a slower return of vision when compared to LASIK (“functional” 20/40 vision on day one, clearing to 20/20 after a few days, vs 20/20 on day one with LASIK) and a little more postop discomfort for the first two to four days when compared to LASIK, which is usually virtually pain-free. In epi-LASIK, an epithelial sheet is lifted mechanically with a microkeratome-like device and the epithelial sheet can be repositioned after laser ablation.

Dr. McDonald says that the literature on epi-LASIK is divided. Some say there is less pain associated with it than with PRK, and others state that it is no less uncomfortable in the early postop period than PRK. She says that while it is extremely rare, with epi-LASIK it is still possible to give the patient a stromal incursion or divot with the dull epi-keratome separator (a very dull “blade” made of plastic or steel). “If this occurs in the periphery of the cornea it's inconsequential, but if it's over the line of sight, it's an issue,” says Dr. McDonald.

She says that while PRK surgeons were quite enthusiastic about epi-LASIK when it was first introduced, and it provided excellent results for thousands of patients worldwide, it has receded significantly in popularity. Although it is still a useful procedure, most surgeons have gone back to PRK or LASEK as their surface ablation procedure of choice.

Non-Laser Procedures

► CK — A Temporary Fix. Conductive keratoplasty's primary indication these days is for patients who have already had LASIK or PRK surgery, are getting older and do not want to use reading glasses. CK is a safe and effective procedure that can extend a patient's ability to be glasses-free for about a year and a half, says Dr. Durrie.

“Similar to a cosmetic product like Botox, CK cannot stop the aging changes in the lens and patients will need additional surgery,” says Dr. Durrie. “Once their arms start getting too short again, I either suggest a CK touch up or that they move on to an IOL.”

Dr. Durrie says not many surgeons are likely to recommend premium IOLs for a 46-year-old piano presbyope with a history of LASIK and excellent distance vision. “CK provides these patients with another option — it's a bridging procedure.”

He says that conductive keratoplasty is great for early presbyopia and that it is economical for both the doctor and the patient, costing patients between $1,000 and $1,800 per eye. “This is an ideal procedure for people who want an alternative to having laser treatment again,” says Dr. Durrie.

Once patients have had CK and it begins to wear off, Dr. Durrie recommends that his patients consider looking at premium IOLs. He lays the groundwork for this next step by educating patients about presbyopia. This makes the move to premium IOLs more palatable.

► Intacs: Low-risk for Low Myopes. Intacs corneal rings (ICR) have made an interesting evolution over the past decade.

Originally approved by the FDA in 1999 as a prescription insert for the correction of mild myopia (1 D to 3 D) and approved by the FDA in 2004 for the treatment of myopia and astigmatism associated with keratoconus, Intacs corneal implants have also emerged as a highly effective off-label treatment for post-LASIK ectasia, with more than 14 peer-reviewed publications on the topic.

However, Addition Technology, the manufacturer of Intacs, reports that there is an ongoing and relatively steady demand for ICRs as a low-risk, removable, durable and safe refractive option for low myopes.

The source of this demand is the huge cohort of low myopes, most of whom do not see themselves as having a serious visual deficit that would warrant permanent correction but who nonetheless would like to achieve improved vision without eyeglasses or contact lenses. Many of these patients are averse to undergoing a laser procedure that may entail even a small degree of risk.

A major benefit of Intacs is that implantation is quick and easy, requiring 10 to 15 minutes per procedure, with a small incision made to enable insertion of the semi-circular rings. Intacs implantation has been demonstrated to be a safe procedure, offering long-term correction.

Inserting Intacs into the cornea essentially flattens the corneal surface. Intacs are designed such that the critical central optical zone of the cornea is left clear, allowing light to focus uninterrupted onto the retina. Corneal asphericity is maintained and no tissue is removed. The structure and function of the eye remains as it was prior to implantation so that surgery with Intacs is fully removable. If the patient's vision changes over time, Intacs segments can be replaced with a different size to match the patient's new needs.

The Near Future

With a multitude of options for correcting spherical error now well established, the next phase of refractive surgery's development is likely to target presbyopia.

Dr. Krueger says that hyperprolate and/or global optimum corneal shape has recently been shown to maintain good distance vision while increasing the depth of focus. “This shape is possible with certain presbyLASIK procedures and even with the IntraCOR procedure,” says Dr. Krueger. “FDA clinical trials and validation are required for this to become a viable alternative. Also, the use of an adaptive optics visual simulator to show this to patients ahead of time would increase its acceptability and understanding with patients.”

The prospects for refractive surgery regaining its position as a mainstream ophthalmic procedure offered in most practices are unclear. General ophthalmologists will continue to be cost-sensitive, particularly given the sticker-shock caused by some newer equipment such as the femtosecond laser, vital though it may be to achieving the best outcomes.

“It seems that consolidation in refractive surgery is bound to happen,” says Dr. Krueger, with larger practices performing the lion's share of a community's refractive surgery and some local ophthalmologists perhaps content to simply refer and co-manage their candidates. “The sophistication and expense of the new technology and the high expectation mentality and market sensitivity of the refractive surgery patient is compelling doctors to be either dedicated to refractive surgery or to concentrate on other general ophthalmology services,” Dr. Krueger says. OM

Reference

1. www.asklasikdocs.com/forums/archive/index.php?t-377.html. Accessed August 13, 2009.