Committee seeks understanding of post-LASIK keratectasia

WAILEA, Hawaii – Many ophthalmologists are unclear regarding what is known and what is not known about post-LASIK keratectasia, and a committee is working to establish a better understanding of the condition through an evidence-based approach, according to a speaker here.

In a presentation here at Hawaiian Eye 2006, Helen K. Wu, MD, described recent efforts by an ad hoc committee to address this gray area in eye care. She and other prominent refractive surgeons are members of the committee, which is headed by Perry Binder, MD, and Richard L. Lindstrom, MD.

The committee began its work, she said, after the now infamous case in which a New York jury awarded $7.25 million – the largest award to date – to a LASIK patient who claims he suffered severe vision damage from the surgery.

“[Following that verdict] it became clear that there was an extreme difference in opinion regarding the extent of knowledge about keratectasia, specifically about what the established risk factors are and when they became the standard of care,” Dr. Wu said.

She said she and her fellow committee members will seek to establish what is known about iatrogenic corneal ectasia – the incidence of which is unknown – and to create a registry of cases induced by LASIK or PRK, “in an attempt to provide an evidence-based approach.”

The group recently published a consensus opinion to summarize current knowledge about corneal ectasia. The paper was published simultaneously in the November/December issue of the Journal of Refractive Surgery and the November issue of the Journal of Cataract and Refractive Surgery.

Committee members also plan to address the matter at upcoming meetings, including a Hot Topics symposium at the American Society of Cataract and Refractive Surgery meeting in March, Dr. Wu said.

While corneal ectasia is rare, there are several known risk factors for its occurrence after LASIK, including high myopia, a deep ablation, an unexpectedly thick flap, low residual stromal bed thickness and abnormal corneal topography, Dr. Wu said. Cases can also develop in the absence of surgery or any risk factors, although these are much less frequent.

Surface ablation to enhance LASIK

Surface ablation techniques can be used to enhance the results of previous LASIK, particularly when the condition of the cornea complicates lifting the flap, according to William B. Trattler, MD.

Dr. Trattler said PRK or laser epithelial keratomileusis may be indicated as enhancement techniques for post-LASIK patients with certain corneal conditions. These conditions can include an insufficient residual stromal bed; consecutive hyperopia after primary myopic LASIK; intraoperative or postoperative flap problems; flaps that are difficult to lift because too much time has gone by since the LASIK procedure; and severe dry eye syndrome.

Dr. Trattler reported on a retrospective study of 89 eyes treated with either PRK or LASEK to enhance previous LASIK. He and colleagues found that “there was a strong trend toward improvement in [best corrected visual acuity]” following the surface ablation procedures. Nearly 100% of the eyes attained 20/40 or better uncorrected visual acuity. And there were no cases of postoperative corneal haze, which can be a major concern after surface ablation, Dr. Trattler said.

He said he believes that there are three keys to success with surface ablation: promoting rapid visual recovery, preventing corneal haze, and minimizing postoperative pain and discomfort.

Surgeons can reduce the risk of postop haze by applying mitomycin-C 0.02% to the cornea after the ablation, Dr. Trattler said. To minimize pain and maximize patient comfort, a careful preoperative dry eye test is essential to determine if the patient should be treated prophylactically with Restasis (cyclosporine, Allergan) and punctal plugs, he said.

Other methods of reducing postop pain include prescribing oral and/or topical nonsteroidal anti-inflammatory drugs, chilling the cornea and using bandage contact lenses, Dr. Trattler said.

Personalized nomogram improves custom ablation

Refractive surgeons can optimize their LASIK results and avoid systematic errors in their patients by adopting a personalized nomogram for custom ablation, according to Yunhee Lee, MD.

Dr. Lee explained that even two surgeons with nearly identical surgical styles, using the same laser in the same laser suite, will have slightly different outcomes when using the same nomogram.

Dr. Lee and colleagues used regression analysis to analyze the results of conventional vs. customized LASIK, as well the results of customized LASIK performed by two surgeons using the same nomogram.

Graphed on a scatterplot, the outcomes of the two surgeons – both using the same customized laser platform, staff, laser suite and technical style – differed by approximately 0.75 D, she said.

She recommended using one of the commercially available software packages for generating a personal nomogram, such as SPSS/SAS, Outcomes Analysis Software, Refractive Surgery Consultant 2000 or Refractive Surgery Consultant Elite.

In creating the personal nomogram, Dr. Lee suggested leaving out variables that are held constant from case to case, such as temperature and humidity, and choosing variables that change, such as age, gender, keratometry and IOP.

“Variables that are held constant from case to case will not alter your outcome and will be one more variable you don’t have to track and analyze,” Dr. Lee said. “Anything you change from case to case could potentially be important in your outcome.”

Above all, she stressed the need to keep the nomogram simple and consistent. She said it is important to “not change things on the fly or month to month based on how you think things are going.”

Visian ICL effective in hyperopia

The STAAR Visian ICL is a good choice for refractive surgical correction in hyperopic patients, according to Paul Dougherty, MD.

Dr. Dougherty said the Visian ICL, which is implanted behind the iris in phakic eyes, is his lens of choice for patients who are under 50 years old with at least 3 D of hyperopia.

“These are some of the happiest patients in my practice,” said Dr. Dougherty, a clinical investigator for the lens who has 3 years of follow-up on some patients.

Addressing the concern that the posterior chamber lens may cause cataracts, Dr. Dougherty said this has not been a significant problem in his experience, but he did say he has seen a small number of lens opacities in his patients.

“These are patients who you would think of doing refractive lensectomy on anyway, so typically the worst thing that can happen is very treatable,” he said.

IOLs in the pipeline

For several IOLs currently in development in the United States, “the story … is still unfolding,” according to I. Howard Fine, MD.

Dr. Fine said the IOLs in development employ a variety of new accommodative mechanisms, photochromic capabilities and other innovative characteristics.

In clinical trials of the Visiogen Synchrony dual-optic accommodating IOL, Dr. Fine said, 100% of 24 eyes had best corrected visual acuity of 20/40 or better at 6 months postoperative, according to data from Visiogen.

Another accommodating design, a deformable IOL from Power Vision, incorporates “new applied microfluidic technology in a single-piece IOL with a ‘dynamic optic,’” Dr. Fine said. When the lens is in place in the eye, microfluidic pumps “reversibly alter the radius of the curvature and effect an increase in IOL power for near vision,” he said.

Dr. Fine also discussed the LiquiLens from Vision Solution Technologies, yet another approach to pseudoaccommodation. Dr. Fine said this device “will provide emmetropia at distance and an accommodative mechanism that allows the lens to achieve three times and above magnification for near.” He said this lens, which is still in the prototype stage, functions based on gravity, and “is the only lens that functions in this way.”

Also under investigation is the Photochromatic Matrix IOL from Medennium. Dr. Fine said in dim-light conditions, this lens behaves like an ultraviolet-blocking IOL.

“Only in photopic conditions does it turn yellow and block blue light,” he said.

Virologist: New antivirals needed in ophthalmic pipeline

Increased commitment from the ophthalmic pharmaceutical industry is needed to ensure the future availability of efficacious ophthalmic antiviral agents, according to an ophthalmic virologist.

Jerold S. Gordon, MD, said ocular viruses such as herpes simplex virus-1, herpes zoster, adenovirus and cytomegalovirus receive relatively little attention and resource allocation from pharmaceutical companies compared to the aggressive funding for more high-profile viruses such as HIV, the SARS Coronavirus and the H5N1 bird flu virus.

“Today there are many viruses for which there is an ambitious effort to develop antivirals,” Dr. Gordon said. “At a conference in China, some $1.9 billion has been committed to finding ways of preventing a possible global [bird flu] pandemic.”

Meanwhile, current ophthalmic antivirals are aging; the most recent drugs in this category were developed more than a decade ago, Dr. Gordon said.

But despite the age of these drugs, some public health officials might not see a compelling need to replace them because the current drugs are still effective, Dr. Gordon said.

He said the current drugs have not allowed resistance to develop because of the mechanism of herpetic latency. Studies have shown that antiviral resistance of HSV-1 is just 0.3% in immunocompetent patients, even though the virus has been exposed to more than 2.3 million kg of combined antivirals over the course of 20 years, he said.

Another possible explanation for the lack of interest in developing new ophthalmic antivirals is a perceived lack of return on investment. The world’s top selling drugs are oriented toward chronic and lifestyle diseases, Dr. Gordon said, not acute conditions.

“Last year, the combined sales for Viagra, Cialis and Levitra passed $3 billion,” he said. “In one nightmarish view of the future, resistant microorganisms will be killing and blinding people, but, fear not, erectile function will be preserved.”

Most alternatives to ophthalmic antivirals have not yet been proved viable, Dr. Gordon said. While there are many vaccines being studied for HSV-1, none has been approved.

Antimicrobial peptides, which are part of the eye’s innate immunity and are effective against bacteria, viruses and fungus, have not been successfully adapted for ophthalmic use, he said.

Even drugs that work in a test tube do not always guarantee clinical success, Dr. Gordon said. “The burden falls on the ophthalmic pharmaceutical companies who are sponsoring this meeting to ensure that we will still have topical antibiotics and antivirals to treat patients in the future,” he said.

Preop antimicrobial lid scrubber to be available

Advanced Vision Research will introduce an antimicrobial lid scrubber that patients can use before cataract or refractive surgery or intravitreal injections, company officials said.

Jeffrey Gilbard, MD, president and chief executive officer of the company, said TheraTears SteriLid will become available over the counter nationwide this spring.

Dr. Gilbard, who developed the product, said in an interview with Ocular Surgery News that patients can use the lid scrubber twice a day for 2 to 3 days before surgery for prophylaxis against endophthalmitis. He said the scrubber can kill up to 40 strains of bacteria.

This article also appeared in Ocular Surgery News, a Slack Incorporated publication.