Femtosecond laser vision correction procedure comparable to excimer ablation

The laser cutting method yielded visual outcomes on par with those of standard excimer laser ablation for mild to moderate myopia.

A femtosecond vision correction procedure offers a new level of precision and a good safety profile, according to a pioneer of the treatment.

ReLEx, a proprietary laser application branded by Carl Zeiss Meditec, allows surgeons to perform vision correction procedures for myopia and myopia with astigmatism using only the company’s VisuMax femtosecond laser.

ReLEx compared favorably with the efficacy, stability and safety of LASIK in a sample of procedures, Osama Ibrahim, MD, told Ocular Surgery News.

“Visual quality was as good as standard excimer laser treatment, and it is a simple and easy procedure,” Dr. Ibrahim said. “Best results were obtained in mild to moderate myopia with astigmatism less than spherical power.”

The ReLEx method comprises femtosecond lamellar extraction (FLEx) performed with the VisuMax femtosecond laser and will allow for a small-incision lamellar extraction (SMILE) in the near future.

Dr. Ibrahim presented study results at the American Society of Cataract and Refractive Surgery meeting in Boston. To date, more than 1,000 ReLEx procedures have been performed outside the U.S., according to a Carl Zeiss Meditec news release.

Versatility, utility

Unlike excimer laser-based LASIK, which relies on tissue ablation, ReLEx offers precise laser cutting.

The VisuMax femtosecond laser operates with a pulse energy of less than 300 nJ, a repetition rate of 500 kHz and spot distance of 2 µm to 6 µm, according to Dr. Ibrahim.

The system works with corneal fixation, which is more precise than scleral fixation. ReLEx requires low suction pressure with a minimal increase in intraoperative IOP that causes no vision loss during suction, Dr. Ibrahim said.

The ReLEx procedure allows flaps that are 0.5 mm to 1 mm larger than the optical zone, a boon to safety and efficacy, he said.

It also enhances patient comfort and requires a short learning curve for surgeons, he said.

“I consider this operation as a one-step procedure,” Dr. Ibrahim said. “It is fast, safe and easy, provided that energy settings are optimized for easy flap and lenticule lifting.”

Aside from ReLEx, the VisuMax femtosecond laser may be used to perform lamellar keratoplasty, penetrating keratoplasty, tissue resectioning and corneal flap cutting, Dr. Ibrahim said.

Study results

The study included 102 eyes of 102 patients. Mean patient age was 27 years (range: 18 years to 63 years). Mean preoperative spherical equivalent was –5.07 D, mean preoperative sphere was –4.38 D, and mean cylinder was –1.38 D.

Inclusion criteria were myopic astigmatism ranging from –1.5 D to –10 D and astigmatism up to –6 D. Patients with excessively flat or steep corneas were excluded.

Exclusion criteria were hyperopia, residual stromal bed thickness of less than 300 µm and the same standard exclusion criteria for conventional excimer laser correction, Dr. Ibrahim said.

Patients were examined preoperatively and at 1 week, 1 month and 3 months postoperatively.

Study results showed that at 1 week after surgery, mean spherical equivalent was –0.16 D, mean sphere was –0.03 D and mean cylinder was –0.27 D (n = 92 eyes).

At 1 month after surgery, mean spherical equivalent was –0.17 D, mean sphere was –0.09 D and mean cylinder was –0.17 D (n = 54 eyes).

At 3 months, mean spherical equivalent was –0.28 D, mean sphere was –0.2 D and mean cylinder was –0.15 D (n = 33 eyes).

Data showed that 95% of eyes were within 1 D of intended refraction at 1 week; at 3 months, 94 of eyes were within 1 D of targeted refraction.

At 1 day postop, uncorrected distance visual acuity was 20/20 in 68% of eyes and 20/25 in 16%. At 1 month, 82% of treated eyes attained uncorrected distance visual acuity of 20/20; at 3 months, 55% of eyes had uncorrected distance visual acuity of 20/20.

In terms of safety, at 1 week after surgery, corrected distance visual acuity improved or remained the same in 78% of eyes. At 1 month, 7% of eyes gained one line, and 14% of eyes gained one line at 3 months. Also at 3 months, more than 2% of eyes gained more than two lines.

At 1 month, 2% of eyes lost more than two lines.

“The rates of intraoperative and postoperative complications are much less than standard microkeratome and excimer procedures,” Dr. Ibrahim said. – by Matt Hasson

• Osama Ibrahim, MD, can be reached at 203-425-2812 or 203-425-2834; e-mail: ibrosama@gmail.com.