Laser refractive surgery gradually regains ground since peaking in early 2000s

According to statistics released by the Refractive Surgery Council, the volume of laser vision correction procedures in the U.S. grew for the third consecutive year in 2018. The overall number of LASIK, PRK and SMILE procedures performed was more than 843,000 last year, representing a 6.2% increase over 2017.

“The reasons may be numerous. The first is that people are starting to better understand and feel comfortable with the safety of the procedures,” Brandon Baartman, MD, said. “With growing numbers of patients out there who are happy with their laser refractive surgery, the myths relating to safety and effectiveness are being dispelled. The broadening adoption of femtosecond lasers to create a bladeless laser procedure has also helped bring it to more people who might have been averse to it originally.”

Corneal refractive surgery hit a peak in the early 2000s, after building momentum over the preceding years. The volume of LASIK alone at that time was approaching 1.4 million procedures per year.

Image: Kathryn M. Hatch, MD

“Baby boomers were very comfortable doing things for themselves and spending money on their own well-being and appearance. Refractive surgery, like any new product, was on the rise. It was what people were doing, what friends were doing. Millennials have a different mindset and different priorities, and there are barriers we have to overcome to reach them. Besides dispelling fears, we should think of new and more targeted marketing strategies,” OSN Technology Board Member Kathryn M. Hatch, MD, said.

New strategies include advertising through social media and keeping up with the pace of change in social media preferences, but also switching to an online appointment system and delivering precise, data-rich information about procedures, taking into account that millennials are a technology-savvy generation.

“Refractive surgery has been and should continue to be a life changer for many people. Though the market was at a standstill, research, technology and therefore indications have grown, and there is a lot more that we can offer now to our patients,” Hatch said.

“Not only do we have access to new techniques like small incision lenticule extraction, but there has also recently been a broadening of treatment algorithms to include astigmatism correction. There are treatment modalities that might expand indications to a larger pool of people, such as patients with irregular corneas that we can treat with topography-guided or wavefront-guided ablation profiles and presbyopic patients,” Baartman said.

LASIK No. 1 in United States

LASIK seems to remain the dominant player in the U.S. refractive market due to its robust track record of safety and effectiveness. It also has some of the broadest indications, including parameters to treat up to 12 D of myopia and 6 D of hyperopia on certain platforms, Baartman said.

The femtosecond laser has brought further improvement to the technique, allowing for more precise and reproducible flap creation.

“It has improved LASIK substantially in the eyes of the patient but also in the hands of the surgeon. The precision and predictability of a femtosecond flap is hard to beat, and it allows for more confidence in preoperative ectasia risk stratification because flap thickness is more predictable. Laser flaps are planar, which may reduce striae formation, are more astigmatically neutral, create less corneal aberration, and result in fewer complications such as epithelial ingrowth or slippage/dislocation, although study results vary,” Baartman said.

Surgeons can now be more confident in their ability to adequately screen patients before surgery. Imaging technologies such as the Oculus Pentacam provide reliable measurements of the posterior cornea, and the understanding of what constitutes a safe corneal thickness and ablation depth profile is improving. Baartman likes to use the percent tissue altered formula to help establish the risk for postoperative ectasia for both LASIK and PRK.

“It helps give me the best idea about what is safe and what is probably too risky,” he said.

Thin and irregular corneas

Thin corneas are stratified by the amount of correction needed to achieve patient satisfaction, generally plano. For some thin corneas, LASIK can be safely performed when a small amount of correction is needed, but the cornea might be too thin for greater correction. PRK might be a better option in those patients.

“Although I think there are biomechanical differences between SMILE and LASIK, I generally consider them in similar corneas. If the cornea is far too thin to consider any type of laser vision correction, I generally offer phakic IOLs,” Baartman said.

In borderline cases, it is important to understand patients’ motivations.

“If they are tolerating their current correction, I always remind them that doing nothing is also an option,” he said.

The ability to treat irregular corneas is expanding to potentially include patients who have been or could be stabilized by corneal collagen cross-linking before being considered a refractive surgery candidate. While still small in overall percentage of the population, patients with early or subclinical keratoconus or other ectatic disorders present frequently to refractive surgery centers for vision correction.

“With the growth of CXL, there have been increasing numbers of reports about post-CXL laser refractive surgery that is helping patients see better in their corrective lenses and sometimes improving uncorrected vision as well. I think this is an area that will continue to see growth in the coming years,” Baartman said.

SMILE on the rise

A dozen years since its inception, ReLEx SMILE has totaled more than 1.5 million procedures worldwide and debuted in the U.S. in 2017. Hatch thinks it is a good procedure that has enriched the options she can offer.

“There is an appeal to SMILE. When you tell your patients that it is a small-incision procedure, this is language they understand, as a small incision is generally preferred to a large incision. After SMILE, there are no restrictions, whereas with LASIK, the patient must be careful with the flap, especially in the immediate postop period. There are also advantages in cases of dry eye because a small incision has a lesser impact on the ocular surface. Regarding corneal biomechanics, we don’t have a definite answer, but there is evidence that SMILE preserves biomechanical stability better than LASIK,” she said.

In her practice, Hatch offers SMILE as first-line treatment to anyone who is a suitable candidate: approximately 50% SMILE, 30% LASIK and 20% PRK. Following approval of astigmatic correction in October, which allows treatment of 0.75 D to 3 D of astigmatism with SMILE, the number of potential candidates has increased.

The inability to treat hyperopia has been so far a limitation with SMILE, but a multicenter study evaluating a new hyperopic profile is currently underway in Europe, India and China.

Results at 1 year of follow-up are encouraging, including cases of high hyperopia and high astigmatism, and patient satisfaction is high, according to one of the principal investigators.

“I am convinced that this procedure is going to take off very successfully in the near future. At our site, to date, we have treated 82 eyes with excellent results, which have remained stable in those who have achieved 1 year of follow-up,” Pavel Stodulka, MD, PhD, said.

The hyperopic lenticule, he said, is thinner in the center and thicker in the periphery to obtain a steeper corneal profile. Dissection and extraction are straightforward, but extra care is needed with the incision because with a larger lenticule the entry is sometimes close to the limbus.

“The well-centered, very large optical zones we can observe on topography would be difficult to achieve with hyperopic LASIK,” Stodulka said.

None of the cases he treated has needed enhancement for residual refractive error, but this is a challenge to figure out how to handle in the future, he said.

Generally speaking, SMILE cannot be enhanced with SMILE, and this is a drawback of the technique, according to Hatch.

“We can do PRK on top of the SMILE cap or do thin-flap LASIK. In both cases, it is not ideal given we initially chose SMILE as alternatives to LASIK and PRK. Ultimately, as long as the patient is a good candidate, I ensure them that we have excellent options for laser vision correction. I emphasize that LASIK is also an excellent, proven procedure for the right candidate which has been around for decades. In the rare event we have to convert to LASIK, I make sure patients are good candidates for it in addition to SMILE, and they understand that they are getting the best possible procedure for them. All my SMILE patients consent to both procedures,” she said.

There are future applications of SMILE that she likes to imagine, including additive procedures in which tissue is put inside the eye.

“Some day the lenticule might be reused rather than discarded to treat conditions such as presbyopia and hyperopia. We could potentially use the pocket to perform cross-linking. Also, very low SMILE treatment could be performed in patients after cataract surgery for residual refractive error,” Hatch said.

PRK: No pain, no haze

Transepithelial PRK is an advancement to a technique that is one of the safest in terms of long-term complications.

“In Canada about 5 years ago, PRK was about 10% of cases. Now it is at least 25%, and in some clinics it is much more. In my clinic, it is now 99%. The trend is slowly more toward PRK because we are now seeing the long-term complications of LASIK. Ectasia does not happen right away, but 4 to 7 years later, with low as much as with high corrections, and very thick corneas are not spared, whereas a –2 D with PRK never develops ectasia. Personally, I have never seen a single case of ectasia with PRK,” David T.C. Lin, MD, said.

Long-term flap complications are also an issue and include femtosecond LASIK flaps, albeit less frequently.

“We have patients who 15 years after LASIK bump into a kitchen cabinet and their flap comes off — this in addition to the short-term flap complications that we all know. With femto, the flap-stroma interface can still come apart. You still get epithelial ingrowth and have to retreat,” Lin said.

Lin has been involved in the development of transepithelial PRK since its beginnings in 2004. The current single-step procedure performed by the Amaris laser platform with SmartPulse and SmartSurfACE technology (Schwind) is a no-touch, continuous technique that combines PTK epithelial removal and PRK stromal ablation.

“The surface is so regular it heals within 2 to 4 days and gives you immediate postoperative vision. We check the patients immediately after surgery, and binocularly they are already 20/40 or better uncorrected, which is just above the threshold for driving without spectacles in North America, a nice baseline vision that makes them functional and allows them to feel comfortable around the house, to look at their phones, send emails, just putting some tear drops in. From then on, it’s routine,” Lin said.

Pain is well managed with one or two drops of NSAIDs after surgery and then for another couple of days at home. This is usually sufficient to have almost no discomfort, while uncontrolled, prolonged use would prevent healing.

The treatment range is from –0.25 D up to –12 D, with up to 7 D of astigmatism.

“It is a huge range, more than we can do with LASIK,” Lin said.

He has treated more than 15,000 patients with trans-PRK and has a long follow-up reaching 15 years in some cases, with no long-term complications.

In his opinion, if the procedure is not more widely adopted, this is because the classic PRK misconceptions — pain, dark room for a week, waiting 1 month for good vision — still persist. It is also because nobody likes to change and nobody likes learning curves.

“If surgeons feel reasonably comfortable with a procedure, they stick to it,” Lin said. “And market competition has a role, since LASIK companies have to protect their market share.”

LASEK still viable

Massimo Camellin, MD, has performed about 1,000 trans-PRK procedures, mainly in irregular corneas. These are the cases in which the transepithelial approach, with addition of mitomycin C, has the biggest advantages, in his opinion. The drawback is that it is a procedure that not all lasers can do and is specifically associated with the Schwind Amaris platform.

For more regular cases, his first choice remains LASEK, the technique that he developed in 1998. His first patient, who underwent PRK 10 days earlier in the other eye, noticed a significant difference in terms of complete absence of pain and encouraged him to go on.

“Many U.S. colleagues disagreed and strongly opposed me on the issue of pain, but there is a simple reason why they were unable to give their patients the painless experience that makes LASEK different from PRK. When the epithelium is separated and repositioned, it should be pressed down firmly to completely adhere to the stromal surface. If it moves, it is lost within half an hour, and what you have done is in fact a PRK,” Camellin said.

Unlike a contact lens, a well-applanated, steady biological flap does not stimulate or rub on nerve endings, allowing for painless recovery. Meanwhile, the new epithelium grows and replaces it.

“This synchronized, gradual replacement of the old with the new tissue prevents the stromal keratocytes from being contaminated by the inflammatory cytokines contained in the tears. This is the second major difference with PRK,” Camellin said.

At a later stage, Camellin adopted the automated procedure for epithelial separation proposed by Ioannis Pallikaris, MD, PhD. This allowed a perfect epithelial flap creation in 99.9% of his cases, including those with strong epithelial adherence and long-term contact lens wearers.

“I was also able to extend the indications to higher amounts of refractive error,” he said, “and never had a single case of posterior ectasia in more than 20 years.”

Hyperopic treatments are also successfully performed, with no postoperative haze and regression using MMC 0.02% for 2 minutes.

Unfortunately, manufacturers of epikeratomes have switched to single-use blades, significantly increasing the cost of what was previously a convenient, affordable procedure. Camellin is currently having new metal, autoclavable blades made by Geuder.

Laser platforms

There is a wide choice of refractive laser platforms available today, but not all are in the U.S. market.

“I think that the ‘best’ platform is often different for different patients. I am fortunate to have had the opportunity to train and to have access now to a variety of systems. I currently use the Alcon WaveLight EX500 for performing wavefront-optimized and topography-guided LASIK and PRK for the majority of patients, and our practice also has access to the Zeiss VisuMax femtosecond laser for offering SMILE to patients as well,” Baartman said.

Other platforms offer different treatment options, such as the wavefront-guided algorithm available on the Johnson & Johnson Vision Star S4 laser system, coupled with the iDESIGN wavefront system.

“In patients with an irregularity to their wavefront or topography, the best treatment option may be a procedure guided by that testing modality. In a normal cornea, I think wavefront-optimized LASIK or PRK performs beautifully. Overseas, I know there has been good success with trans-PRK, but we do not have access to lasers with that capability over here,” he said. – by Michela Cimberle

References:

Adib-Moghaddam S, et al. J Cataract Refract Surg. 2018;doi:10.1016/j.jcrs.2018.07.021.

Bohac M, et al. Semin Ophthalmol. 2018;doi:10.1080/08820538.2018.1539183.

Camellin M. J Refract Surg. 2008;doi:10.3928/1081597X-20080501-02.

Lin DTC, et al. J Refract Surg. 2017;doi:10.3928/1081597X-20170920-02.

Moshirfar M, et al. J Cataract Refract Surg. 2018;doi:10.1016/j.jcrs.2018.07.047.

Number of LASIK surgeries in the United States from 1996 to 2020 (in 1,000). Statista website. www.statista.com/statistics/271478/number-of-lasik-surgeries-in-the-us.

Parafita-Fernández A, et al. J Cataract Refract Surg. 2018;doi:10.1016/j.jcrs.2018.07.020.

Reinstein DZ, et al. J Refract Surg. 2019;doi:10.3928/1081597X-20181025-01.

Taneri S, et al. J Cataract Refract Surg. 2019;doi:10.1016/j.jcrs.2018.08.030.

Wang M, et al. Transl Vis Sci Technol. 2018;doi:10.1167/tvst.7.5.11.

Wen D, et al. J Refract Surg. 2018;doi:10.3928/1081597X-20180905-01.

For more information:

Brandon Baartman, MD, can be reached at Vance Thompson Vision Omaha, 11819 Miracle Hills Drive, Suite 203, Omaha, NE 68154; email: brandon.baartman@vancethompsonvision.com.

Massimo Camellin, MD, can be reached at SEKAL Microsurgery, Via Jean Henri Dunant, 45100 Rovigo, Italy; email: massimo.camellin@sekal.it.

Kathryn M. Hatch, MD, can be reached at Massachusetts Eye and Ear Waltham, 1601 Trapelo Road, Suite 184, Waltham, MA 02451; email: kathryn_hatch@meei.harvard.edu.

David T.C. Lin, MD, can be reached at Pacific Laser Eye Centre, 1401 W. Broadway, Vancouver, BC V6H 1H6; email: tclin@shaw.ca.

Pavel Stodulka, MD, PhD, can be reached at Gemini Eye Clinic, U Gemini 360, 760 01 Zlín, Czech Republic; email: stodulka@lasik.cz.

Disclosures: Baartman reports he is a lecturer for Alcon, and a consultant for Refocus Group, Allergan and Equinox. Camellin reports no relevant financial disclosures. Hatch reports she is a consultant for Carl Zeiss Meditec. Lin reports he is a consultant for Allergan and Shire. Stodulka reports he is a consultant for Bausch + Lomb.

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