Small-incision lenticule extraction yields stable astigmatic correction

Small-incision lenticule extraction performed exclusively with a femtosecond laser was shown to treat myopia and myopic astigmatism, a study showed.

The intrastromal refractive procedure resulted in few complications and high patient satisfaction, the study authors said.

“The refractive outcome was very stable and very predictable and was comparable to the excimer laser procedures,” Rupal Shah, MS, the corresponding author, told Ocular Surgery News. “And even more so in very high myopia.”

Astigmatic correction was particularly stable, Dr. Shah said.

“If a patient had myopic astigmatism with significant cylinder, sometimes we would find regression of refraction. Here I found that the refraction was more stable than in any kind of laser procedure,” she said.

ReLEx SMILE (small-incision lenticule extraction), a variant of ReLEx FLEx (femtosecond lenticule extraction), is performed with the VisuMax femtosecond laser system (Carl Zeiss Meditec) with a 200-kHz repetition rate.

The prospective study was part of a pre-marketing clinical study sponsored by Zeiss and published in the Journal of Cataract and Refractive Surgery.

Patients, procedures

The study included 51 eyes of 41 patients who underwent ReLEx SMILE. The study only included eyes with myopia or myopic astigmatism of less than 10 D.

The femtosecond laser was used to cut an intrastromal lenticule, which was removed through a 3-mm to 5-mm incision. The incision involved a 30° to 40° side cut.

Primary outcome measures were Snellen corrected distance visual acuity, uncorrected distance visual acuity and manifest refraction. Corneal topography and ocular wavefront aberrations were also measured.

Patients were evaluated postoperatively and at 1 week, 1 month, 3 months and 6 months. A questionnaire was used preoperatively and postoperatively to gauge subjective symptoms such as dry eye, pain and glare. Symptoms were graded on a scale ranging from 0 (no symptoms) to 3 (severe symptoms). Satisfaction scores ranged from 0 (highly dissatisfied) to 10 (highly satisfied).

Safety, predictability

Mean spherical equivalent was –4.87 D at baseline and 0.03 D at 6 months postoperatively. All eyes were within 1 D of targeted refraction at 1 month and 6 months. Postoperative refraction appeared to be stable within 1 month after surgery.

The difference in mean postoperative spherical equivalent was less than 0.25 D between 1 month and 6 months; the difference was statistically insignificant.

Corrected distance visual acuity at 6 months postop equaled or exceeded preop corrected distance visual acuity in 95% of eyes. Also at 6 months, 79% of all eyes that underwent attempted full refractive correction had uncorrected distance visual acuity of 20/25 or better.

No eyes lost more than two lines of corrected distance visual acuity at 3 months. Two eyes lost one line of corrected distance visual acuity and one eye lost one line at 3 months.

Data showed statistically significant increases in root mean square higher-order aberrations at 6 months (P < .01), comparable to increases found in other studies of wavefront-optimized LASIK.

Dr. Shah noted that postoperative visual recovery the day of surgery and the next day was relatively slow.

Subsequent procedures performed using the VisuMax femtosecond laser with a 500-kHz repetition rate yielded better immediate postoperative outcomes, Dr. Shah said.

Low complications, high satisfaction

The only complications or adverse events at 3 and 6 months were reports of mild dryness by patients. There were no reports of increased halos, double vision or diminished night driving vision. However, some patients reported diminished sensitivity to bright light and less visual fluctuation at night.

Some patients reported mild dryness of the eye, the authors said, but possibly at a lower incidence than that associated with femtosecond LASIK.

All patients reported high satisfaction with the procedure. – by Matt Hasson

Reference:

• Shah R, Shah S, Sengupta S. Results of small incision lenticule extraction: All-in-one femtosecond laser refractive surgery. J Cataract Refract Surg. 2011;37(1):127-137.

• Rupal Shah, MS, can be reached at New Vision Laser Centers, 303, Siddarth, R.C. Dutt Road, Vadodara, Gujarat 390007, India; 91-937-627-1000; e-mail: rupal@newvisionindia.com.
• Disclosure: Dr. Shah is a consultant for Carl Zeiss Meditec.

The study of Shah and colleagues gives clear evidence of further development of the ReLEx procedure through a small incision (SMILE). Indeed, when compared to the first study published by our group in the British Journal of Ophthalmology in July 2010 where 91 eyes were followed up for 6 months, the ±0.5 D predictability improved from 80.2% to 91% in Dr. Shah’s study. She also further minimized the size of the entering incision and also used one instead of two opposite incisions as in our initial study. Another possible reason for the better outcome is that Dr. Shah used a commercial type of the VisuMax laser, whereas we treated our patients using a prototype of this machine. While Dr. Shah confirms our results on higher-order aberrations in terms of coma, the increase of spherical aberration of +0.11 as compared to 0.008 in our study is worrisome. One could only speculate, if the surgical parameters chosen (anterior cup of 100 µm and lenticule diameter of 6 mm as compared with 120 µm and 6.5 mm, respectively, in the study by Sekundo et al) might explain the difference in the results. In summary, this new paper gives an important contribution to the evolving technique of flapless intrastromal refractive surgery producing better outcomes and using even smaller incisions than in the first study published.

– Walter Sekundo, MD
Professor and Chairman, Department of Ophthalmology, Philipps University Marburg, Germany
Disclosure: Dr. Sekundo is a consultant for Carl Zeiss Meditec.