Today’s LASIK candidates better targeted

Jul 12, 2023

With more than 20 million procedures performed to date in the U.S., LASIK is still the most popular and most performed laser vision correction method, according to the Refractive Surgery Council.

Since the inception of LASIK in the early 1990s, it has evolved through several milestone advances in technique and technology, which have increased safety, efficacy, precision and quality.

“I had the honor of being in the FDA-monitored trials on LASIK in the early ’90s, and the way we were doing LASIK then doesn’t really resemble the way we do it now,” Healio | OSN Refractive Surgery Board Member Vance Thompson, MD, said. “In my almost 30 years of LASIK, safety and patient satisfaction have gone up immensely.”

Results have continued to improve in terms of visual outcomes and quality of vision.

“With the amazing technology we have today, if a patient is not 20/15 after LASIK, I’m surprised and actually disappointed,” Deepinder K. Dhaliwal, MD, LAc, said.

Improved outcomes are also the result of better patient selection. With the advances in phakic IOL technology, the options for correcting refractive error have expanded, and the indications for LASIK have become more specific.

“Because we have so many wonderful options of refractive surgery techniques now, we don’t have to ‘push the envelope’ as we sometimes did when we only had excimer laser refractive surgery,” Dhaliwal said.

“We don’t push the upper limit of LASIK now. Taking a comprehensive approach to refractive surgery has lessened the indications for LASIK, expanded the refractive surgery market, and made the LASIK outcomes safer and better,” Thompson said.

The approach begins with a comprehensive diagnostic model in which not only the cornea but the whole eye is evaluated, along with the patient’s subjective responses and lifestyle factors.

“Our respect for the tear film has grown immensely over the years, not only therapeutically but optically since the majority of focus power and image quality happens at the air-tear interface level. If you don’t have a smooth tear film, you are not going to have smooth vision,” Thompson said.

Advancements in diagnostic modalities provide multiple objective parameters to interpret distinct functions of the tear film.

“For tear film analysis, we use the Trukera ScoutPro device, and then we look at topography and epithelial mapping because they also give us indicators of tear film health. The LipiView device (Johnson & Johnson Vision) shows us tear film stability and tear film breakup time, and it helps us to image the meibomian glands. Those new technologies have been very helpful in supplementing the traditional exams to assess epithelial health of the conjunctiva and cornea. Consequently, tear film treatment has also evolved significantly,” Thompson said.

Advanced epithelial mapping with the MS-39 anterior segment OCT (CSO) or other similar devices is becoming a must-have, in his opinion, for both refractive and cataract surgery. Specific indices help to identify early keratoconus and epithelial irregularities that might affect the optical quality of the eye.

“I use the term ‘epithelial blur.’ If the epithelium is irregular, it makes the tear film irregular in the air-tear interface, scattering light and creating blur. Epithelial mapping combined with tear film analysis, topography and tomography provides a wide range of highest-quality data and measurements for preoperative evaluation and decision-making,” Thompson said.

A simple method for understanding whether blurry vision is a surface-related issue or an internal issue is the time-honored over-refraction using a gas permeable contact lens.

“If the refraction was blurry without and is crisp with the gas permeable contact lens, we know it’s the tear film, epithelium or anterior stroma of the cornea that needs to be treated,” Thompson said.

The Oculus Pentacam is the gold standard for topography and tomography. It provides important data for determining susceptibility to ectasia as well as clues regarding dysfunctional lens syndrome and early cataract. Ultrasound pachymetry is also used when necessary to measure corneal thickness.

Wavefront measurement is a modern-day diagnostic to help analyze the optical quality of the eye, Thompson said. He uses the Nidek OPD-Scan III to analyze the higher-order aberrations of the internal eye and the cornea. He also uses the WaveScan system (Johnson & Johnson Vision) and recently acquired the WaveDyn vision analyzer (WaveFront Dynamics), a dynamic aberrometry measurement system.

The back of the eye is then evaluated by exam and, if indicated, macular OCT.

Finally, genetic testing can be used in a complementary fashion to find out if there are tendencies toward keratoconus or other corneal dystrophies.

“It is an evolving part of refractive surgery screening. Most of my U.S. colleagues now use the Avellino genetic test as an adjunct when they feel they need a tiebreaker, but we still have a lot to learn about genetic testing and need to acquire more data,” Thompson said.

In the last 2 or 3 years, the incidence of LASIK has increased markedly.

“People realize how important good visual acuity is. Coming out of COVID, there was an increased demand for better vision, also driven by the increased use of computers,” Healio | OSN Cornea/External Disease Board Member Eric D. Donnenfeld, MD, said.

The high quality of results with the latest technologies has also been an important driving factor in increasing the demand.

“The two most recent advances in the United States are wavefront technology and topographic ablations. In the FDA trials of advanced wavefront technology, specifically Visx (Johnson & Johnson Vision), 79% of patients achieved 20/16 or better, and patient satisfaction was 98%,” Donnenfeld said.

The Alcon Contoura topography-guided LASIK treatment showed similar results in the FDA trial, with 69% of patients achieving 20/16 or better and 31% achieving 20/12 or better.

“I have used the Contoura system extensively and find that it achieves a very high level of quality of vision. But what makes it extraordinarily exciting for me is the ability to treat irregular corneas. Patients with previous surgery such as RK — older laser treatments that were performed 20 years ago — and, most notably, patients with keratoconus can now have their eyes corrected,” Donnenfeld said.

Laser vision correction becomes a therapeutic correction for patients who otherwise would be relegated to hard contact lenses or maybe even require corneal transplantation.

Wavefront ablations have been around for many years, but the iDesign platform by Johnson & Johnson Vision raised it to the next level, incorporating 1,200 data points into the wavefront ablation.

“With the added data points, there is five times more resolution than previous technology. And again, this has led to many patients having a gain of BCVA,” Donnenfeld said.

Automated ray tracing optimization is an additional step forward in customized LASIK technology. The Phorcides ray tracing optimization software for Contoura with the WaveLight EX500 excimer laser is not yet available in the U.S. but has shown promising results in studies.

“John Kanellopoulos, MD, has used this extensively. It allows you to use AI to customize a model for every patient to create more predictable and improved outcomes with laser vision correction, evaluating the entire eye. This is a welcome addition into the laser vision correction market, something that I’m looking forward to experiencing here,” Donnenfeld said.

Femtosecond technology has revolutionized flap creation in LASIK and is now the gold standard for the procedure.

“I used microkeratomes from the early days, many different types of microkeratomes and different iterations. There is no question that predictability and safety are so much better with femtosecond laser for flap creation. We can really offer a superior outcome because of our ability to control the thickness and the consistency of flap thickness from periphery to the center,” Dhaliwal said.

Femtosecond laser-created flaps heal in place more strongly in the periphery as compared with mechanical microkeratome-created flaps. Dislocation rarely occurs even in cases of ocular trauma.

“Although the flaps are a bit more difficult to relift in case of re-treatment, this is rarely necessary with our improved technology: wavefront-guided ablations, active eye tracking, cyclotorsion correction with iris registration provided by our current lasers. The ablation is perfectly centered, and we are able to create sophisticated ablation patterns. Even if patients are moving their eyes, the laser tracks the movements very precisely. We don’t see the issues that we had before. It’s just so much more precise and predictable,” Dhaliwal said.

She recalled occasional decentered ablations that used to occur in the past due to poor patient fixation.

“They no longer happen because we are imaging the eye ahead of time, we are registering that image at the time of the ablation, and we have sophisticated eye-tracking systems. This is what I tell my patients all the time: I used to be the eye tracker. If the patients moved, I lifted my foot off of the laser pedal. Thank goodness, those days are over,” she said.

The major problems with LASIK in the past have been identified and largely solved, Donnenfeld said.

Dry eye used to be a common complaint following LASIK, but now, with thinner flaps and the ability to recognize dry eye preoperatively, patients are more carefully selected and pretreated if they are at risk for postoperative dry eye.

Glare and halos were also a problem earlier on with LASIK but are now less common.

“We have added blend zones, customized ablations and optimized ablations to reduce glare and halos, and we have expanded the ablation zones. That has been a major change in laser vision correction,” Donnenfeld said.

Flap complications were common with microkeratomes but do not occur today with the use of femtosecond laser.

“We recognized a complication, and we found a solution. Now, things like flap complications and decentration sound almost archaic,” Donnenfeld said.

However, Dhaliwal said that she is still referred cases of LASIK complications that are avoidable and offered some useful advice.

“No. 1, it is very important to optimize the ocular surface ahead of time to avoid seeing severe dry eye after LASIK,” she said.

Patients with preexisting dry eye should be made aware that dry eye symptoms may temporarily get worse after the procedure but can be minimized by treating the surface preoperatively.

Intraoperatively, it is important not to use drops that have a viscous vehicle because they can cause severe inflammation.

“It is really important to understand what types of drops you are putting in the patients’ eyes,” she said.

Third, the postop day 1 exam is critically important and must be performed by a skilled observer who is able to detect early signs of diffuse lamellar keratitis (DLK).

“DLK is seen on day 1, and if you detect it early and treat it aggressively, it resolves without any issue. But if you miss it initially, it worsens, and patients who get to stage 4 DLK can have permanent vision loss,” Dhaliwal said.

Other complications such as infection are minimized by proper perioperative techniques and avoiding the potential sources of microbes, such as tap water, near the operating field.

“LASIK is performed in a clean but not sterile environment, so we must be very careful to avoid contamination. When doing bilateral surgery, we use two different sets of instruments, one for each eye, to avoid cross contamination. We still drape the eyelid and lashes, and we use infection prophylaxis with antibiotics before and after surgery,” she said.

Patients should be warned that laser vision correction is still eye surgery, and caution is necessary for at least 2 weeks before they go back to their regular routine.

“They have to be mindful of what types of activities they are doing immediately after LASIK so that they don’t jump in a swimming pool, for example, or get hit with a baseball or a tennis ball,” Dhaliwal said.

Last but not least, surgeons should strongly recommend avoiding eye rubbing, as this can be detrimental, even years after surgery.

“I tell everybody not to rub their eyes because the cornea is a little thinner than it was before and to avoid positions that place pressure on the eye during their sleep. I have had patients coming in a decade after LASIK with ectasia only in one eye because they always sleep on that side,” Dhaliwal said.

“With the evolving technology for refractive surgery, LASIK candidacy has both constricted and expanded,” Donnenfeld said.

High-quality laser vision correction can be offered to patients who could not be considered candidates before because the new technologies allow treatment of more irregular corneas. In addition, corneal cross-linking can be used in combination with LASIK in eyes at risk for ectasia.

On the other hand, the development of IOL technology has narrowed down the choice of LASIK to a more select patient population.

“Up to +3 D of hyperopia and –8 D of myopia is what I consider the sweet spot of LASIK. Higher than that, we could start reducing the potential image quality and contrast sensitivity, so I think about phakic IOLs and lens replacement in patients with higher corrections,” Thompson said.

“I used to do 300 LASIK cases a month because we only had LASIK or PRK, but now we have the EVO ICL (STAAR Surgical) for high myopia as well as premium IOLs for refractive cataract surgery or refractive lens exchange, and my LASIK volume has deliberately gone down,” Healio | OSN Board Member Mitchell A. Jackson, MD, said.

He now performs LASIK in patients younger than 38 years of age; older than that, he considers refractive lens exchange with the Light Adjustable Lens (LAL, RxSight), especially in patients with abnormal objective scatter index (OSI) as seen on the HD Analyzer (Keeler). For patients with myopia of –8 D or more, he considers the EVO ICL as an option if the OSI is normal. The central opening in the lens has greatly improved safety, preventing angle closure and cataract formation.

“We may have different cut-off points, depending on the technology we are using. And accurate diagnostics is key. We have a large array of technology now to help drive good decision-making,” he said.

With modern LASIK, a good percentage of patients can now achieve 20/15 or even 20/10 vision, but what makes the difference is that side effects are essentially eliminated now, and patients are happy.

“In the past, we were able to achieve really good vision, but not all patients were happy because of the residual aberrations we were not able to manage or even to predict,” Jackson said.

Corneal aberrations or lenticular aberrations resulting from early lens changes can now be detected preoperatively.

“The newer software essentially eliminates all the clinically significant aberrations from the cornea. But patients who don’t have a normal objective scatter index on their preop evaluation with the HD Analyzer and are near presbyopic age may have a stage 1 or 2 dysfunctional lens, or early cataract. We don’t do LASIK in these patients now because they would still have complaints with 20/20 vision, and we have wonderful IOL options to propose instead,” he said.

Jackson’s practice has converted more into a refractive cataract surgical practice in recent years, but he stressed the point that LASIK, PRK and now SMILE are indispensable options.

“With the LAL, you do the adjustments on the lens itself, but with any other multifocal IOL, if you are off target, you must be able to offer laser enhancement. With aberrometry and new formulas, our precision has increased, but nothing is perfect yet. AI will take us a further step forward, but a thing called healing is still going to be there, so personal and unpredictable,” he said.

Whenever possible, LASIK is the best choice for refractive IOL surgery enhancement because it provides the fastest recovery for patients who already are anxious because they feel something may have gone wrong with the first surgery.

The changing and expanding landscape of refractive surgery options has made LASIK outcomes better, he said.

“The technology for LASIK is so much better than it was in the past when I started in 1995, and yet I do less LASIK now. It may seem a contradiction, but it is not. I used to do LASIK on everybody, even for –20 D in the old days, but we know better now what we should and should not do with our refractive armamentarium,” Jackson said.

Click here to read the Point/Counter to this Cover Story.