LASIK popularity remains, but surface procedures are viable alternatives

Okihiro Nishi, MD, said PRK is “superior” to LASIK in some cases especially those where a flap is in danger of being removed. Image: Nishi O

LASIK represents the preferred refractive procedure performed worldwide today, but surface ablation techniques — PRK, LASEK, epi-LASIK and epi-LASEK — should be a part of every refractive surgeon’s armamentarium and the first choice to treat specific cases.

“Generally in Japan, people prefer LASIK, and PRK is not so popular because it is known as a rather painful procedure with relatively late recovery of vision. However, I would never offer LASIK to professional or amateur boxers or to those who perform martial arts such as karate, judo or aikido, because the LASIK flap could be torn off. I always perform PRK in these patients, and there are also other cases in which PRK is superior to LASIK,” Okihiro Nishi, MD, director of the Nishi Eye Hospital, Osaka, Japan, said.

“As a surgeon, I have no preference for either PRK or LASIK, but in Australia, surface ablation has never been popular amongst patients,” Michael Lawless, MD, OSN Asia-Pacific Edition Associate Editor, said. “It is a practice killer in some ways. Patients tolerate the procedure because they have to but don’t enjoy the experience. In my practice, I do PRK for specific indications, in about 15% of the cases.”

In Europe, a relatively small number of practices perform mainly surface ablations, according to Daniel Epstein, MD, PhD, a professor of ophthalmology in Bern, Switzerland.

“There are practices where LASIK is still the majority, but there is a positive trend toward surface ablation, up to 20% of the total volume of refractive surgery. This is happening also in some practices in the U.S. and in other countries like Israel, where PRK is enjoying great popularity at the moment,” Dr. Epstein said.

Massimo Camellin, MD, who developed LASEK in 1998, uses his technique and its epi-LASEK variation, which is epi-LASIK with the use of alcohol, for all treatments: myopia, hyperopia and astigmatism.

“For 12 years, I have been using surface ablation exclusively within a certain range of correction,” he said.

The scenario is constantly changing because the technology evolves, Michiel Luger, MD, medical director of VisionClinics, Utrecht, the Netherlands, said.

“We have done refractive surgery for about 12 years. At first, we mainly did LASIK; then we changed to around 50% to 70% PRK, and when the femtosecond laser emerged, we switched back to LASIK with thin flap. We do now 70% LASIK and 30% PRK. If the patient is suitable for both procedures and motivated to do LASIK, I do LASIK, but there are a lot of circumstance in which PRK is preferable,” he said.

Indications, range of correction

The main indication for surface ablation is a thin cornea, below 500 µm or even 480 µm for some surgeons.

“I appreciate that the science on this is debatable, but I have some clear parameters. A cornea less than 500 µm thick is an indicator to perform PRK rather than LASIK,” Dr. Lawless said.

Dr. Lawless also takes into account asymmetry between the corneas, posterior float, inferior/superior steepening ratio, patient age and family history.

“When in doubt, I proceed with PRK or phakic IOL rather than LASIK,” he said.

Surgeons agree that surface ablation is mandatory if patients have professions with a heightened risk of eye trauma, such as police officers or firefighters, or after-work activities that could involve being hit in the eye, such as basketball, tennis or golf.

There are also specific circumstances dictated by bureaucracy. The Royal Australian Air Force, for instance, mandates that pilots receive PRK instead of LASIK.

Both Dr. Epstein and Dr. Luger said that it is important to listen to what the patient wants. Patients today are well-informed, and many have specific requests. One of the most frequent concerns is the need to go back to work as soon as possible.

Dr. Nishi performs PRK for the correction of postoperative refractive errors and anisometropia after cataract surgery and IOL implantation.

“These errors are usually minimal in equivalent diopters, so we have observed no case with relevant haze,” he said.

Surgeons’ opinions show considerable variation in the range and type of refractive error treated with surface procedures as opposed to LASIK.

Dr. Nishi reserves PRK for low myopia, up to 4 D to 5 D. Over this range, he said, there is a higher risk of postoperative haze, even with the use of mitomycin C.

“I use LASIK up to –8 D, and above that I implant phakic IOLs,” he said.

Dr. Epstein, on the other hand, thinks that the risks connected with treating a higher refractive error are greater with LASIK than surface procedures.

He treats with PRK up to –7 D or –8 D of spherical equivalent, depending on corneal thickness.

“I might go above those limits from time to time with PRK, but I would never do it with LASIK,” he said.

Michael Lawless

Dr. Lawless treats up to 7 D of myopia and 3 D of astigmatism with PRK.

“I look at corneal anatomy and correlation between the magnitude and axis of refractive vs. keratometric astigmatism,” he explained.

Dr. Luger treats with either PRK or LASIK in a refractive error range between –0.75 D and –10 D.

Dr. Camellin treats hyperopia with surface ablation. He uses LASEK or epi-LASEK for all his cases.

“With the use of mitomycin C 0.02%, the problem of haze is avoided entirely. I correct up to –10 D of myopia and also hyperopia up to +4 D and astigmatism up to 6 D. No more than this, to preserve visual quality,” he said.

In his view, surface treatments can be used for higher corrections than LASIK, not only in consideration of the risk of ectasia, but also because larger optical zones can be ablated and because, with no flap, there is more tissue depth available.

Advantages of surface treatments

An advantage of surface procedures as compared with LASIK is the increased safety in relation to corneal biomechanics and complications.

“They have no effects on corneal biomechanics, and we can therefore treat higher refractive errors with larger optical zones,” Dr. Camellin said.

First described by Seiler and colleagues in 1998 and later reported by several other authors, surgically induced ectasia has cast a shadow over the reputation of LASIK.

“After so many years and all the precautions we have adopted to avoid it, ectasia still remains an issue.” Dr. Epstein said. “The increased safety of femtosecond-laser LASIK, with or without [a] thin flap, has yet to be established. Ectasia might develop 5 to 7 years after the procedure, and though the femtosecond laser has been around for so long, it has had a limited amount of users. It will be years before we have a sufficient number of procedures to draw significant conclusions.”

Dr. Lawless and colleagues published a case earlier this year of unilateral keratectasia in a laser refractive surgery patient.

In this patient, LASIK was performed in the first eye with a femtosecond laser. In the second eye, due to difficulty in lifting the flap, the procedure was converted to PRK.

“Neither eye had risk factors for keratectasia; both had identical low scores on the Randleman risk factor score,” the study said.

Three months after surgery, ectasia was found in only the LASIK eye, in which the cap was lifted.

“A benefit of surface ablation as opposed to LASIK is the near certainty that surface ablation will not result in ectasia,” Dr. Lawless said.

According to Dr. Camellin, a flap, whether it is created with a femtosecond laser or a microkeratome and despite how thin it is, inevitably alters corneal biomechanics.

“The point is that you always cut the Bowman’s, which is like an elastic bandage that holds the cornea together. By doing this, you weaken the cornea,” he said.

With surface ablation, only a small 5- to 6-mm area of Bowman’s membrane is affected centrally; then the treatment goes more superficial, toward the periphery. But the LASIK flap is a large dissection of Bowman’s membrane that is, in his opinion, the cause of ectasia.

Another advantage of surface techniques is that all flap-related complications, such as buttonholes, diffuse lamellar keratitis, free flaps or epithelial ingrowth, are avoided, Dr. Nishi said.

“Also, femtosecond-created flaps have risks,” Dr. Camellin said. “Suction loss, tissue bridges, gas breakthrough and other complications may occur. Thin flaps are no better. They more easily have folds on top of all the other complications of thicker flaps. We can handle these problems, of course, but they are better avoided. Surface ablation is easier and safer.”

Quality of vision, according to some surgeons, is also better after surface treatment. Contrast sensitivity and wavefront results with PRK may be better than with LASIK.

“In addition, the regression in refraction is less associated with PRK in my experience,” Dr. Nishi said. “Postoperative refraction stands more stable.”

Drawbacks of surface ablation

Drawbacks of surface treatments are some degree of postoperative pain, the discomfort of wearing a contact lens for a few days and a longer visual rehabilitation as compared with LASIK.

“The postoperative course of surface ablation remains, in spite of all precautions, significantly more difficult. In my view, everything is negative compared to LASIK, ranging from discomfort, slow recovery of vision, corneal hyperesthesia and sensitivity even years later and, very rarely these days, corneal haze and scarring,” Dr. Lawless said.

However, he said that the use of mitomycin C has made PRK more acceptable.

“I use it routinely at 0.02% for 15 seconds, and this allows the near elimination of haze,” he said.

Dr. Epstein said pain management can be achieved; however, patients cannot immediately return to work following PRK.

“All variations of PRK are the same in this respect: They all need a few days to heal and a few weeks to 1 month to achieve full visual recovery,” he said.

Considerable reduction of pain is obtained with LASEK and its variations, if a correct postoperative management protocol is applied, according to Dr. Camellin. One drop of antihistamine just after surgery, together with preservative-free NSAIDs and corticosteroids, should be applied.

“Antihistamines are mediators of pain, and it is important to block out pain right at its onset,” he said.

Pressure on the flap and a contact lens should be applied with the Johnston applanator (Rhein Medical) to squeeze out the fluid and make the flap adhere firmly to the stromal surface.

“This helps keeping the flap, which is mandatory in the first 24 hours to avoid pain, and is what makes LASEK different from PRK,” Dr. Camellin said.

Of his patients, 90% report no pain 1 day after surgery, and 10% have complaints that range from a mild burning sensation to pain. If a higher rate of pain is reported in some papers, this is mostly because recommendations are not followed, he said.

A newly developed technique with one specific laser has taken PRK forward in minimizing pain and shortening the healing process, according to Dr. Luger.

It is a no-touch, all-laser transepithelial approach in which the epithelium is removed by the laser after the refractive correction has been performed. An algorithm calculates the correction in the corneal stroma minus the epithelium, and it is known exactly how much of the epithelium will be removed. The laser is accurate and minimally traumatic, which leads to a faster healing process. Dr. Luger noted that the contact lens, which was previously removed at 4 days, is now removed at 2 to 3 days.

“Postoperative pain is also less than in conventional PRK. Fewer patients complain, and those who do seem to suffer less and for a shorter time,” he said. “It’s a quick, very precise, very effective procedure. Not many surgeons use it because there’s only one machine doing it, but in our practice the amount of PRK has increased a lot since we have introduced it. We treat around 6,000 patients per year in this practice, and around 1,000 are PRK with transepithelial approach.”

The future

It is difficult to say in what proportion surface and lamellar procedures will be used in the future, but they are likely to continue to coexist.

Dr. Nishi believes that LASIK will remain the principle technique for the correction of myopia under 8 D and for hyperopia, while PRK will continue to be used for low myopia and postoperative refractive error after cataract surgery.

“For high myopia, phakic IOLs will undergo further improvement and will be used increasingly more in the future, but I do not think that they will replace cornea-based refractive surgery. The refractive outcome is more accurate with LASIK or PRK, particularly in low degrees of myopia and hyperopia, compared to phakic IOLs,” he said.

In his opinion, PRK has the potential to surpass LASIK, but the problem of haze needs to be addressed more effectively.

“Haze is the major drawback of the technique. A little delay in visual rehabilitation doesn’t seem much of an issue compared with the potential flap complications of LASIK,” Dr. Nishi said.

According to Dr. Camellin, the chance of experiencing some pain for a few days or 1 week of relative inability to work is a small price to pay for the high safety profile of surface techniques.

“They are a minor inconvenience compared to the short- and long-term hazards of LASIK. But LASIK has won the largest share on the market based on two of the most appealing concepts in our society: no pain and instant gratification. Selling these ideas is a tremendous marketing strategy,” he said.

However, people are beginning to change their priorities. A small but increasing number of patients are prepared to pay the price of initial discomfort in view of long-term safety.

“Of course you need to speak clearly to them and be objective about the pros and cons of the two procedures,” Dr. Epstein said.

According to Dr. Lawless, the relative proportion of surface procedures has increased in recent years because of the fear of ectasia after LASIK, and it has now stabilized.

“The balance between the two procedures is about right at present. What could alter it in favor of LASIK is a better test to determine which corneas are truly at risk of ectasia. I am sure we are overestimating the risk at present. Conversely, what could alter it in favor of PRK is a better form of contact lens or topical medication to make recovery quicker and more comfortable,” Dr. Lawless said. – by Michela Cimberle

Would you consider PRK as a re-treatment after LASIK?

References:

• Camellin M. Laser epithelial keratomileusis for myopia. J Refract Surg. 2003;19(6):666-670.
• Camellin M. Laser epithelial keratomileusis with mitomycin C: indications and limits. J Refract Surg. 2004;20(5 Suppl):S693-698.
• Camellin M. What about LASEK? J Refract Surg. 2008;24(5):462.
• Camellin M, Wyler D. Epi-LASIK versus epi-LASEK. J Refract Surg. 2008;24(1):S57-63.
• Epstein D. Refractive surgery. Ther Umsch. 2009;66(3):207-210.
• Hodge C, Lawless M, Sutton G. Keratectasia following LASIK in a patient with uncomplicated PRK in the fellow eye. J Cataract Refract Surg. 2011;37(3):603-607.
• Neira-Zalentein W, Moilanen JA, Tuisku IS, Holopainen JM, Tervo TM. Photorefractive keratectomy retreatment after LASIK. J Refract Surg. 2008;24(7):710-712.
• Seiler T, Koufala K, Richter G. Iatrogenic keratectasia after laser in situ keratomileusis. J Refract Surg. 1998;14(3):312-317.
• Vinciguerra P, Randazzo A, Albè E, Epstein D. Tangential topography corneal map to diagnose laser treatment decentration. J Refract Surg. 2007;23(9 Suppl):S1057-1064.

• Massimo Camellin, MD, can be reached at SEKAL, Via Dunant 10, 45100 Rovigo, Italy; phone/fax: +39-0425-411357; email: cammas@tin.it.
• Daniel Epstein, MD, PhD, can be reached at Bernese Eye Research Institute, Switzerland; +41-0041-31-3114822; email: epstein.dan9@gmail.com.
• Michael A. Lawless, MD, can be reached at Vision Eye Institute, 270 Victoria Ave., Chatswood, NSW 2067, Australia; +61-29-424-9999; fax: +61-29-410-3000; email: michael.lawless@vgaustralia.com.
• Michiel Luger, MD, can be reached at VisionClinics, Postbus 85337, 3584 AA Utrecht, The Netherlands; +31-30-7114804; fax: +31-30-7114819; email: luger@visionclinics.nl.
• Okihiro Nishi, MD, can be reached at Nishi Eye Hospital, Osaka, Japan; email: okihiro@nishi-ganka.or.jp.
• Disclosures: Dr. Lawless is on the medical advisory board of Alcon/LenSx and Nexis Vision. Dr. Camellin, Dr. Epstein, Dr. Luger and Dr. Nishi have no relevant financial disclosures.