FS-SURGERY

All-femtosecond laser refractive surgery produces good visual outcomes with greater stability and fewer side effects than conventional LASIK, according to a series of studies presented at the annual meeting of American Society of Cataract and Refractive Surgery. Known as ReLEx SMILE, for small-incision lenticule extraction, the procedure uses a Carl Zeiss Meditec VisuMax femtosecond laser to cut a refractive lenticule in stromal tissues along with a 3.0mm to 4.0mm incision through the corneal epithelium and Bowman’s membrane. The lenticule interfaces are then separated manually using a flap dissector and the lenticule is removed in one piece through the small incision. An earlier ReLEx procedure known as FLEX is similar except the lenticule is removed through a flap instead of a small incision.

“This all-femtosecond laser refractive surgery is a flapless procedure which permits minimally invasive refractive correction,” said Jean-Francois Faure MD, Espace Nouvelle Vision, Paris, France. Unlike LASIK, his HRT and OCT exams of post-op SMILE eyes showed no degradation of corneal nerves, which Dr Faure believes promotes quicker recovery. In the largest series reported at the ASCRS conference, Osama Ibrahim MD, Alexandria University, Egypt, found SMILE refractions extremely stable. From a preoperative mean spherical equivalent of -5.92 +/- 2.13 D, he reported postoperative SE means ranging from -0.09 +/- 0.39 D for 975 eyes at one month to -0.07 +/- 0.37 D for 266 eyes followed to 12 months.

“These patients maintained vision at one month, three months, six months and one year. The patients followed up to two years showed exactly the same results,” he reported. At one year, 95 per cent of SMILE patients were within 1.0 D of the target refraction, and 73 per cent were within 0.25 D, Dr Ibrahim reported. About five per cent lost one line of corrected distance vision, while 26 per cent gained one line and seven per cent gained two lines. Over time, patients tended to recover lost vision, he added. Arturo J Ramirez-Miranda MD, Instituto de Oftalmologia “Conde de Valenciana,” Mexico City, reported similar results in a prospective interventional case series involving 113 eyes in 58 patients with a mean preoperative SE of -5.0 D, ranging from -1.25 to -7.88 D. Between three and 12 months after surgery, only four per cent of patients saw refractions change more than 0.5 D.

“At one year, 97 per cent were 20/20 or better uncorrected, with two per cent losing one line of corrected distance visual acuity while 27 per cent gained one line and seven per cent gained two lines,” Dr Ramirez-Miranda said. Mean SE measured -0.21. Predictability was 98 per cent, with 94 per cent within 1.0 D SE of intended correction and 81 per cent within 0.5 D. For astigmatism, 90 per cent were within 1.0 D, and 54 per cent within 0.5. Igor Solomatin MD, Riga, Latvia, one of the earliest SMILE researchers, presented a series of 60 eyes in 30 patients with a preoperative SE of -4.53 +/- 1.29 D. He reported 95 per cent predictability, with all eyes within 1.0 D of intended refraction, 92 per cent within 0.5 and 40 per cent within 0.13 at one year. Also, 98 per cent achieved 20/25 or better uncorrected, 86 per cent 20/20 and 54 per cent 20/16 or better. About 12 per cent lost one line of corrected distance vision while 34 per cent gained one to two lines.

A contralateral eye study involving 20 patients comparing SMILE and femto-LASIK, also done at Conde de Valenciana in Mexico City, found no statistical significance in refractive outcomes, said Angie De La Mota MD. Predictability was 97 per cent in both groups, with 79 per cent of LASIK and 93 per cent of SMILE eyes within 1.0 D, and 64 and 71 per cent, respectively, within 0.5 D of the intended refraction. No significant differences were found in postoperative tear film breakup time, Schirmer test or corneal aesthesiometry, Dr De La Mota said. Patient satisfaction also was similar, with a slight trend toward SMILE.

However, in his study of 110 eyes evaluating postoperative corneal interfaces, Dr Faure noted that 2/3 had stopped artificial tears one month after surgery, more than he typically sees after LASIK. Microscopic examinations revealed less inflammation in the corneal epithelium, Bowman’s membrane, and mid-stroma beyond the lenticule in SMILE eyes than in LASIK eyes. Similar levels of inflammatory cells were seen in the area of lenticule extraction in SMILE patients as in the anterior stroma of LASIK patients, though with unidentified hyperreflective particles in the SMILE eyes. This, along with maintaining corneal nerves, may account for less dry eye after surgery.