Refractive surgery technology advances may expand options for surgeons, patients

US surgical trends in refractive error correction have vacillated substantially over the years, with surface ablation and LASIK gaining and losing popularity as new drugs and technologies emerge.

Enhancements that reduce postoperative pain and haze led to a resurgence in the use of surface ablation procedures; topical NSAIDs, topical dilute anesthetics and oral medications ease recovery, and intraoperative mitomycin C lessens visual complications. However, the advent of femtosecond laser platforms for LASIK again turned the tides, improving the precision and safety of a procedure that began to lose popularity amid concerns over potential flap complications.

Considering such history, the future of refractive correction may provide challenges for patients when they are weighing their surgical options and the advantages and disadvantages of these options. While most surgeons agree that neither surface ablation nor LASIK will disappear, differing opinions exist regarding the short-term evolution of surgical preferences. Some foresee stability, predicting that surgeons will continue to perform LASIK for a majority of patients. Others believe that innovations such as corneal collagen cross-linking will increase the prevalence of surface ablation.

“I think surface ablation is coming back into vogue,” Richard W. Yee, MD, said. “We are coming full circle again. While making specialized flaps with the femtosecond laser has improved outcomes for refractive surgery, we are probably going to go back and start doing more surface [ablation] again, because of the innovation of cross-linking agents and because of a better understanding of drugs and approaches to reduce the major risks of surface ablation, namely pain and haze.”

Dr. Yee and colleagues started the International Congress on Surface Ablation about a decade ago, and he said that this year’s meeting featured significant research on corneal collagen cross-linking with riboflavin, a procedure used to treat conditions such as ectasia and keratoconus. These conditions weaken the cornea and might otherwise disqualify patients from refractive correction.

Other surgeons are less confident in the renewed popularity of surface ablation, which includes primarily PRK in the United States but may also refer to LASEK, epi-LASIK or epi-LASEK.

“Surface ablation has a significant role and is a viable part of our surgical arsenal. … I do not think PRK is going away right now. But I do not see it growing in popularity either,” Eric D. Donnenfeld, MD, OSN Cornea/External Disease Board Member, said.

Surface ablation at present

According to Dr. Donnenfeld, the cost of PRK and LASIK is the same, and he considers each procedure appropriate for different populations. He performs PRK on roughly 12% of patients, reserving it for those who cannot undergo LASIK.

“Determining when LASIK and when PRK are the optimal procedures for the patient is important to improve patient outcomes. Both PRK and LASIK offer patients visual rehabilitation and relieve them from the handicap of poor uncorrected visual acuity, which results in improved quality of life and patient satisfaction,” he said.

Dr. Donnenfeld performs PRK on younger patients, those with thin, irregular corneas, patients who underwent prior LASIK and require only surgical enhancements, those with occupations that preclude laser surgery, and individuals who have superficial corneal scars or epithelial basement membrane dystrophy. For the latter group, he removes surface opacifications while providing visual rehabilitation.

Daniel S. Durrie, MD, performs surface ablation procedures in about 25% of patients. Image: Kenny Johnson Photography

People who participate in mixed martial arts or work for certain military divisions should not risk potential flap complications, nor should those with thin corneas, Daniel S. Durrie, MD, OSN Refractive Surgery Section Editor, said. He performs surface ablation on roughly 25% of patients and includes those with anterior basement membrane dystrophy or loose skin on the eye and individuals with various types of prior surgery, including LASIK, radial keratotomy, corneal transplants and cataract surgery.

“The procedure that I use now is alcohol-assisted PRK. It is proven, in comparison to other surface ablation procedures, to have the fastest visual recovery and the lowest discomfort,” he said.

Dr. Durrie treats the same range of refractive error, +3 D to –8 D, regardless of whether he performs LASIK or PRK.

William B. Trattler, MD, OSN SuperSite Board Member, said that he will treat up to –10 D with surface ablation; however, only 10% of his virgin cornea patients are treated with surface ablation.

“Patients who are more myopic will be associated with more regression and increased risk of haze, but with the use of mitomycin C, we have been able to reduce that to a negligible amount,” Dr. Donnenfeld said.

While the recovery time for PRK remains inferior to that for LASIK, modifications continue to minimize the procedure’s postoperative discomfort and complications. For example, a prospective, randomized study published in the Journal of Refractive Surgery suggested that off-label use of Neurontin (gabapentin, Pfizer) may significantly reduce pain after PRK.

Moreover, while mitomycin C is considered the gold standard for eliminating postoperative haze, this complication may be avoided altogether, according to Dr. Yee, if patients are examined for ocular surface disorder before surface ablation.

“If anyone sees hazing, it is because the patient has an ocular surface disorder of some kind: dryness, meibomian gland dysfunction, aqueous dry eye, exposure to certain environments. … The key in treatment is to get rid of those irritants, protect the surface, and therefore that haze does not develop,” he said.

PRK vs. LASIK

The long-term popularity of LASIK is attributed to speedy recovery and lessened discomfort, but renewed enthusiasm stems from the introduction of femtosecond laser technology, which is said to create safer, more precise flaps.

“In my experience, surface ablation was gaining popularity but has dropped more recently with the wide availability of the femtosecond laser. … We have gotten good with surface ablation, providing solid visual results and a less uncomfortable postoperative experience. The problem is the early postoperative vision. The vision is poor for a number of days, compared to LASIK where you have a fast visual recovery,” Dr. Trattler said.

Some surgeons believe that, despite advanced surface ablation techniques, LASIK is a more effective, safer procedure.

“LASIK with a femtosecond flap is more comfortable, provides more rapid visual rehabilitation, yields better refractive results and, most importantly, is safer for our patients,” Dr. Donnenfeld said. “There is less risk of infection with LASIK, because healing takes place in 4 hours rather than 4 days, and there is less chance for microbial agents to penetrate the eye.”

Dr. Donnenfeld said that thinner, smoother flaps with reverse side cuts have substantially reduced the incidence of dry eye and nearly eliminated the occurrence of flap folds.

“The reverse side cuts that we are using on a regular basis allow the flap to adhere more accurately and with greater strength, so the complications that we saw with flap formation using keratomes have almost disappeared,” he said.

However, according to Dr. Durrie, PRK requires less equipment and less intraoperative time, approximately 3 minutes per eye, and many patients prefer not having the risk of flap complications.

“I think surgeons like LASIK or [sub-Bowman’s keratomileusis] procedures better, because they do not have as much follow-up and patients are happier quicker,” he said.

Dr. Yee stopped performing LASIK almost 10 years ago to avoid possible complications such as neuropathy of the corneal ocular surface. He said that such neuropathy may exacerbate one of the more common postoperative issues of LASIK: dry eye.

Richard W. Yee

“There is more precision, more ability to customize and probably increased safety now that we have femtosecond lasers to make flaps, but still, you are making a flap,” Dr. Yee said. “There is zero chance of having a flap complication when you do not make one.”

LASEK and epi-LASIK

Other advanced surface ablation procedures generated enthusiasm among U.S. surgeons a few years ago, but interest has declined.

“There was some hope several years ago that epithelial preservation techniques such as epi-LASIK were going to be superior procedures, but we have learned that these procedures are really no different than PRK,” Dr. Donnenfeld said, emphasizing that they do not quicken visual recovery or improve discomfort.

Some ophthalmologists even suggest that the procedures are less effective than PRK.

“I quit doing epi-LASIK and LASEK. They did not make the vision come back faster. Actually, it [came back] a little slower,” Dr. Durrie said.

During LASEK, surgeons lift the thin epithelial layer of the cornea from the ocular surface, preserving it while laser reshaping occurs. For epi-LASIK, a variation of LASEK, ophthalmologists use a plastic blade known as an epithelial separator to detach a portion of the epithelial layer.

Dr. Yee rarely performs PRK and instead favors LASEK, which he said is significantly more popular in Europe.

“[LASEK] just got a bad reputation in the United States, because I do not think people knew how to do the procedure properly,” he said.

According to Dr. Yee, surgeons try to keep the epithelial layer alive intraoperatively even though it eventually dies. He believes that discontinuing this practice would enhance surgical outcomes.

“You want to take that [epithelial layer] off and just let it die, because the stuff underneath this carpet layer is called basement membrane, and the basement membrane has ingredients and proteins that fool the eye so that it does not create a scar. So that is the advantage of LASEK,” he said.

Additionally, trying to keep the cells alive through dissection with ethyl alcohol is problematic, because the cells can stay in alcohol for only about 20 seconds, he said. This makes pulling the layer down more difficult, often resulting in a tattered flap.

“By using anywhere from 45 seconds to a minute of alcohol, the flap comes down easily, and you put it right back,” Dr. Yee said. “But again, everyone thinks they cannot use [the alcohol] that long, because they want the cells to be living.”

Literature trends

Recent journal publications and U.S. ophthalmic meeting presentations illustrate the ups and downs of PRK and LASIK, as well as the uncertainty surrounding the future of refractive error correction.

For example, a contralateral analysis published by Dr. Durrie and colleagues in 2008 found equivalent visual outcomes and faster recovery for LASIK as compared with PRK, and the 2009 LASIK world literature review by Solomon and colleagues showed a 95.4% satisfaction rate among patients, drawing its conclusions from 309 journal articles published internationally between 1988 and 2008.

However, a retrospective case series that included all patients who underwent refractive surgery at the Wilmer Laser Vision Center between 2007 and 2009 reported at least a 30% decrease in laser procedures and an overall increase in PRK (P = .05). Moreover, the 2010 American Academy of Ophthalmology/International Society of Refractive Surgery survey on U.S. trends in refractive surgery likewise demonstrated an increase in PRK, suggesting that while LASIK still dominated for patients with error between –8 D and +3 D, surface ablation was on the rise.

Eric D. Donnenfeld

As reported by Dr. Donnenfeld and colleagues, the introduction of femtosecond laser platforms decreased LASIK safety concerns, leading to the current popularity of LASIK.

However, as befits the path of refractive error correction, a study published in 2011 may raise questions regarding the safety of femtosecond LASIK.

A prospective, masked, randomized pilot study by Hatch and colleagues, which included 52 eyes that underwent contralateral PRK and thin-flap LASIK with a femtosecond laser, showed that while the two procedures achieved similar outcomes in visual acuity, contrast sensitivity and induction of higher-order ocular aberrations, a higher proportion of eyes that underwent thin-flap LASIK experienced complications.

“While thinner LASIK flaps attempt to preserve the biomechanical stability of the corneal stroma, at the same time, the flap itself becomes less stable, as was noted with the two flap tears and other complications occurring in the thin-flap LASIK group in this study,” the authors wrote.

Future of the procedures

Considering the meandering history of surface ablation and LASIK, as well as the range of expert viewpoints and evolving clinical findings surrounding these procedures, the future of refractive error correction leaves much to the imagination.

“The reason LASIK is popular is because it provides fast recovery and minimal discomfort. If you had a technology that allowed for rapid visual recovery after surface ablation, that could be a game changer and make it gain further popularity,” Dr. Trattler said.

William B. Trattler

Dr. Durrie and his research team are working on ways to reduce PRK recovery time.

“I do not think it will ever be as fast as the LASIK/[sub-Bowman’s keratomileusis] procedures, but if we can make the vision recover equal to LASIK within a few days, I think it will become more popular,” Dr. Durrie said.

In terms of LASIK advancements, Dr. Trattler foresees corneal reshaping, similar to the IntraCor technique (Technolas Perfect Vision), which could eliminate the need for a flap. Such enhancements might further alleviate long-term safety concerns regarding LASIK, which have prompted a joint investigative effort between the U.S. Food and Drug Administration, the National Eye Institute and the U.S. Department of Defense.

This effort, known as the LASIK Quality of Life Collaboration Project, is a three-part study that was launched in 2009 to determine patients’ postoperative quality of life. Some surgeons are hopeful that its outcomes will further validate the use of laser procedures.

“I think the LASIK quality of life initiative is going to be a landmark work that will once and for all show the efficacy and safety and patients’ acceptance of LASIK, as well as how it improves patients’ quality of life,” Dr. Donnenfeld said.

In addition to modifications to PRK and LASIK, U.S. researchers are evaluating PRK in combination with the off-label use of corneal collagen cross-linking and riboflavin to treat refractive error and conditions such as keratoconus simultaneously.

Various studies have already suggested the efficacy and safety of same-day PRK followed by cross-linking. According to Dr. Yee, if this combined procedure achieves widespread popularity, the number of patients treated with surface ablation will likely increase. Cutting into a destabilized ocular structure, as would be necessary during LASIK, is not preferred for patients with such corneal conditions, he said.

“Cross-linking gives us an opportunity to treat patients who would otherwise not have been able to be treated, because their corneas were not stable or strong enough to undergo such a treatment,” Dr. Yee said. “You obviously would never cut into the cornea again if it is already weak, so that is why surface ablation is the approach that will probably be used.” – by Michelle Pagnani

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References:

• Duffey RJ, Leaming D. US trends in refractive surgery: 2010 ASCRS survey. Presented at: American Academy of Ophthalmology meeting; Oct 16-19, 2010; Chicago.
• Durrie DS, Slade SG, Marshall J. Wavefront-guided excimer laser ablation using photorefractive keratectomy and sub-Bowman’s keratomileusis: a contralateral eye study. J Refract Surg. 2008;24(1):77-84.
• Hatch BB, Moshirfar M, Ollerton AJ, Sikder S, Mifflin MD. A prospective, contralateral comparison of photorefractive keratectomy (PRK) versus thin-flap LASIK: assessment of visual function. Clin Ophthalmol. 2011;5:451-457.
• Kanellopoulos AJ, Binder PS. Management of corneal ectasia after LASIK with combined, same-day, topography-guided partial transepithelial PRK and collagen cross-linking: the Athens protocol. J Refract Surg. 2011;27(5):323-331.
• Krueger RR, Kanellopoulos AJ. Stability of simultaneous topography-guided photorefractive keratectomy and riboflavin/UVA cross-linking for progressive keratoconus: case reports. J Refract Surg. 2010;26(10):S827-S832.
• Kuo IC. Trends in refractive surgery at an academic center: 2007-2009. BMC Ophthalmol. 2011;11(11):1-6.
• Kymionis GD, Kontadakis GA, Kounis GA, et al. Simultaneous topography-guided PRK followed by corneal collagen cross-linking for keratoconus. J Refract Surg. 2009;25(9): S807-S811.
• Kymionis GD, Portaliou DM, Diakonis VF, et al. Management of post laser in situ keratomileusis ectasia with simultaneous topography guided photorefractive keratectomy and collagen cross-linking. Open Ophthalmol J. 2011;5:11-13.
• Lichtinger A, Purcell TL, Schanzlin DJ, Chayet AS. Gabapentin for postoperative pain after photorefractive keratectomy: a prospective, randomized, double-blind, placebo-controlled trial. J Refract Surg. 2011;27(8):613-617.
• Solomon KD, Fernández de Castro LE, Sandoval HP, et al; Joint LASIK Study Task Force. LASIK world literature review: quality of life and patient satisfaction. Ophthalmology. 2009;116(4):691-701.

• Eric D. Donnenfeld, MD, can be reached at Ophthalmic Consultants of Long Island, 2000 North Village Ave., Rockville Centre, NY 11576; 516-766-2519; email: eddoph@aol.com.
• Daniel S. Durrie, MD,can be reached at Durrie Vision, 5520 College Blvd., Suite 200, Overland Park, KS 66211; 913-491-3330; fax: 913-491-9650; email: ddurrie@durrievision.com.
• William B. Trattler, MD, can be reached at the Center for Excellence in Eye Care, 8940 N. Kendall Drive, Suite 400-E, Miami, FL 33176; 305-598-2020; fax: 305-274-0426; email: wtrattler@gmail.com.
• Richard W. Yee, MD, can be reached at The Robert Cizik Eye Clinic, Memorial Hermann Medical Plaza, 6400 Fannin St., 18th Floor, Houston, Texas 77030; 713-559-5200; fax: 713-795-0733; email: ryee3@comcast.net.
• Disclosures: Dr. Donnenfeld is a consultant for Alcon, Bausch + Lomb, AMO and TLC Laser Eye Centers. Dr. Durrie is a clinical investigator for Alcon and AMO. Dr. Trattler is a consultant for AMO. Dr. Yee has no relevant financial disclosures.