Study: Combined SMILE, CXL safe for keratoconus

Mexico City-Combined small-incision lenticule extraction (SMILE) and intrastromal collagen crosslinking (CXL) to treat forme fruste keratoconus is safe, efficient, accurate, predictable, and stable for at least 1 year, according to Enrique O. Graue Hernandez, MD, MSc.

The treatment options for keratoconus have changed dramatically over the past decade, Dr. Hernandez said.

“However, only CXL has successfully stopped progression of keratoconus, while LASIK is contraindicated and the use of photorefractive keratectomy is debatable,” he explained.

Dr. Hernandez and colleagues from the Cornea and Refractive Surgery Department, Instituto de Oftalmologia Fundación Conde de Valenciana, Mexico City, performed a prospective, interventional case series of patients 21 years or older with keratoconus who had a corrected distance visual acuity (CDVA) of 20/40 or better that was stable for at least 1 year. The spherical equivalent to be corrected was less than 10 D and there was 5 D or less of astigmatism. Importantly, the expected residual corneal thickness was more than 400 µm before CXL was performed.

Six patients (10 eyes) (mean age, 29.5 years) underwent a standard SMILE procedure. After removing the lenticule and determining the integrity of the tissue, riboflavin was injected into the stroma every 5 minutes for 15 minutes, or until the cornea was completely impregnated with riboflavin. The cornea was then irradiated for 30 minutes.

The patients were followed preoperatively for an average of 11.1 months. Six eyes completed 15 months of follow-up.

The mean preoperative spherical equivalent (–4.69 D) was successfully corrected almost to plano (–0.154 D) (p <0.001). The uncorrected distance visual acuity also was corrected from 20/400 to 20/25 (p <0.001). As expected, the CDVA did not change. Ninety percent of eyes remained within 0.5 D of the attempted correction, and all remained within 1 D of the attempted correction.

No eyes lost more than two lines of vision, Dr. Hernandez reported.

“Most importantly, over the past year, the results of the procedure were stable,” he commented. “Only one eye had regression of slightly more than 1 D during follow-up.”

Dr. Hernandez explained that the rationale for combining the two treatments is straightforward-maintenance of the strongest part of the cornea, while reinforcing its strength and correction of the refractive error.

“The combined procedure might be superior to PRK and CXL because it is painless, provides faster visual recovery, is performed easily, and has a lower risk of infectious keratitis,” he said. “Compared with implantation of phakic IOLs, there are no inherent risks of intraocular surgery, such as development of cataract, high IOP, or progression. Compared with intracorneal rings, the combined procedure is more predictable.

“The combined SMILE and CXL procedure in this series of patients was safe, effective, accurate, predictable, and stable,” Dr. Hernandez continued. “It may be a promising option for structural and refractive treatment of keratoconus, but this must be confirmed in larger patient series with longer follow-up periods.”

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