Combined refractive lenticule extraction + CXL promising

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Encouraging results are being achieved with simultaneous refractive lenticule extraction and intrastromal collagen crosslinking in patients who are not candidates for excimer laser vision correction procedures.

Dr. Adballa

By Cheryl Guttman Krader; Reviewed by Moones Abdalla, MD

Cairo-Combined refractive lenticule extraction with intrastromal collagen crosslinking (CXL) might be a safe, predictable, and stable refractive surgery option when conventional laser vision correction is contraindicated because of abnormal topography, said Moones Abdalla, MD.

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In previous research, it was found that unlike LASIK, the SMall Incision Lenticule Extraction (SMILE) technique does not adversely affect corneal biomechanics, said Dr. Abdalla, medical and research director, International Femto Laser Centre, Cairo, Egypt.

“More recently, we corroborated that finding with newer technology for evaluating biomechanical stability,” Dr. Abdalla said. “We reasoned that combining CXL with SMILE in eyes with forme fruste keratoconus (FFKC) or early keratoconus could strengthen the cornea to stop the progression of the ectatic disease while meeting patient demands for good unaided vision.”

NEXT: Evaluating the combined procedure + Videos

Evaluating the combined procedure

Dr. Abdalla and colleagues at the International Femto Laser Centre undertook a prospective evaluation of the combined procedure for patients with a topographic diagnosis of FFKC.

Further reading: Study: Combined SMILE, CXL safe for keratoconus

Refractive lenticule extraction was performed using the SMILE technique, a proprietary procedure in which a femtosecond laser (VisuMax 500, Carl Zeiss Meditec) is used to create a refractive lenticule in the stroma that is removed through a small side incision.

In all cases, the lenticule was created with a 100-µm cap and leaving 300 µm of residual stromal bed. After the lenticule was removed, isotonic riboflavin was injected into the intrastromal pocket three times at 5-minute intervals. The CXL procedure was completed with 5 minutes of UVA irradiation at a fluence of 18 mW/cm².

NEXT: Patients and findings

Patients and findings

Dr. Abdalla presented results from follow-up through 1 year from a series of 19 eyes of 10 patients treated for mild-to-moderate myopia with astigmatism. At last follow-up, mean SE was –0.14 D (range –1.25 to +1.5 D) and mean astigmatism was –0.38 D. Nearly three-fourths of eyes had an achieved SE within 0.5 D of target and 89% were within 1 D. Mean uncorrected visual acuity (UCVA) (Snellen decimal) was 0.82.

All cases showed topographic stability during the follow-up, no eyes lost more than 2 lines of best spectacle-corrected visual acuity, and assessment of biomechanical stability showed no significant changes after surgery.

Patients were eligible for the treatment if their refraction and topographic findings were stable for at least 1 year, best-corrected visual acuity (BCVA) was better than 0.7, central corneal thickness was >460 µm, and they were at least 21 years of age. The group had a mean age of 29.4 years, and preoperative refraction showed mean sphere was –3.97 D (range –6 to –1.25 D) and mean cylinder was –2.85 D (range –0.75 to –4.25 D).

UCVA data showed that visual recovery was limited initially by the presence of postoperative haze in all eyes, but as the haze resolved, visual acuity improved. Mean UCVA was 0.54 at 1 week, improved to 0.67 at 1 month, and remained stable after reaching 0.84 at 6 months. Three eyes lost 1 line of BCVA and 2 eyes lost 2 lines of BCVA due to haze. There were no other safety issues.

“The slow visual recovery is the downside of this procedure,” Dr. Abdalla said. “Patients must understand that the end visual results are good, but it might take several months to reach their best vision.”

NEXT: Conclusion

Biomechanical stability was assessed by correlating IOP and deformation amplitude measured using a device combining corneal imaging and Scheimpflug technology (Corvis ST, Oculus). The data showed mean IOP was unchanged from the preoperative level throughout follow-up. Mean deformation amplitude was 1.38 mm, 1.19 mm at 1 month postoperatively, and stable thereafter.

“Our early results are encouraging, and based on that experience we are performing the combined procedure in more patients,” Dr. Abdalla said. “Data from longer follow-up in larger populations is definitely needed.”

Moones Abdalla, MD

E: moones_abdalla@hotmail.com

Dr. Abdalla has no financial interest in the products discussed.