EyeWorld Asia-Pacific June 2011 Issue

20 June 2011 EW REFRACTIVE Although the femtosecond laser is safe and precise, it can result in complications, such as epithelial ingrowth, pictured here Source: Edward J. Holland, MD Despite high predictability, complications, such as cutting an epithelium-only flap, can still occur T he femtosecond laser has added a new layer of precision to LASIK flap creation, and research suggests that it is a remarkable, though not error-free, device. A new report by George D. Kymionis, MD, PhD, lecturer, Institute of Vision and Optics, Faculty of Medicine, University of Crete, Heraklion, Greece, and colleagues, found that a femtosecond inadvertently cut an epithelium-only flap. It was then necessary to convert the procedure to a PRK. “Despite the high predictability and safety of the femtosecond laser in terms of flap thickness, complications may occur,” Dr. Kymionis reported. Notably, Ioannis G. Pallikaris, MD, PhD, Heraklion, who performed the first LASIK procedure in 1989 and developed the epi-LASIK procedure, co-authored the study. Dr. Kymionis added that complications of the femtosecond procedure include epithelial and subepithelial gas breakthrough, visually significant epithelial ingrowth, incomplete flaps, and subconjunctival gas bubble formation. Of course, he noted, microkeratomes have their own set of complications, which include decentered or free flaps, buttonholes, epithelial abrasions, and irregular flap edges. In this study, published online in June 2010 in the Journal of Refractive Surgery , Dr. Kymionis investigated only a single case report of epithelium-only flap creation. He also mentioned that the femtosecond has a “high incidence of reproducibility and stability”, opening a “new chapter in ophthalmology”. Still, potential complications need to be understood. A case of torn flaps Dr. Kymionis performed LASIK on a 28-year-old man with a corrected distance visual acuity of 20/20 (6/6) in both eyes but who only had counting fingers vision uncorrected at distance in both eyes. Manifest refraction was –6.75 –0.75 x 5 in the right eye and –7.00 –0.50 x 180 in the left eye. “Taking into consideration corneal thickness and refractive error, the surgeon decided to proceed with LASIK using the IntraLase iFS System [Abbott Medical Optics, Santa Ana, Calif., USA],” Dr. Kymionis repoted. “A corneal flap with a superior hinge was created using the IntraLase iFS laser (150 kHz). The laser parameters in both eyes were: attempted flap thickness 100 µm, flap diameter 8.25 mm, spot/line separation 6 µm/6 µm, bed energy of 1.10 µJ, superior hinge position Femtosecond procedures may result in complications by Matt Young EyeWorld Contributing Editor Views from Asia-Pacific CHAN Wing Kwong, MBBS(S’pore), MMed(Ophth), FRCS(Edin), FRCOphth, FAMS Visiting Consultant, Singapore National Eye Centre 11 Third Hospital Avenue, Singapore 168751 Eye & Retina Surgeons #13-03 Camden Medical Centre, 1 Orchard Boulevard, Singapore 248649 Tel. no. +65-6738-2000 Fax no. +65-6738-2111 wkchan@me.com C reating the flap with a femtosecond laser has made LASIK better and safer, but unexpected complications unique to femtosecond laser flaps can still occur. This could be bubbles in the anterior chamber and vertical gas breakthrough. Epithelial ingrowth, incomplete flaps, irregular flaps and decentered flaps can still occur with the femtosecond laser, just like with a microkeratome. Epithelium-only flaps with a femtosecond laser can occur when starting the flap dissection too superficially, resulting in epithelium-only flaps. Torn flaps can occur because of thinner than expected flaps made with the femtosecond laser. Although the thickness of the applanation cone can contribute to the variability of the flap thickness, this variation is usually in the region of 10-15 microns and is unlikely to cause an epithelium-only flap. More likely reasons are the inaccurate calibration of the femtosecond laser for flap thickness and low suction or loss of suction with the patient interface. Epithelium-only flaps have also occurred with microkeratomes and are not unique to femtosecond laser flaps. The management of epithelium only flaps can be by conversion to PRK with adjunct MMC application, or simply replace the epithelium, put on a bandage contact lens and re-attempt the flap creation a week later with the femtosecond laser set at a thicker flap thickness—say, 120 microns. As for torn flaps, if the tear is partial, the refractive ablation can still be done and the flap replaced and aligned carefully. Use of a bandage contact lens is helpful in this situation. If the flap is completely torn and avulsed from the corneal hinge, conversion to PRK with adjunct MMC application would be the best approach. In my experience, femtosecond laser flap complications are far fewer and rarer than microkeratome flap complications. Even if a flap complication occurs with the femtosecond laser, a repeat procedure can usually be done within a day or a week later, compared with microkeratome flap complications where no repeat procedure can be attempted for 3-6 months. This “quick recoverability” of femtosecond laser flap procedures is the greatest advantage of the femtosecond laser over a mechanical microkeratome. Editors’ note: Dr. Chan has no financial interests related to his comments.