EyeWorld Asia-Pacific December 2012 Issue

37 EWAP REFRACTIVE December 2012 Cordelia CHAN, MD Head & Senior Consultant, Refractive Surgery Service Senior Consultant, Cornea & External Eye Disease Service Singapore National Eye Centre 11 Third Hospital Avenue, Singapore 168751 Tel. no. +65-62277255 cordelia_chan@snec.com.sg F emtosecond LASIK flap creation has drawn negative criticism recently in the article “Femtosecond flaps in the ditch”. In this article, suction breaks and haze were highlighted as complications seen with femtosecond platforms that could result in an undesirable LASIK outcome. Suction break is a potential problem in any system that involves docking and applanation on the cornea. In fact, in the days when LASIK was performed exclusively with the microkeratome, suction breaks were a devastating complication, often resulting in partial, incomplete or irregular flaps necessitating postponement of the surgery and eventual loss of best corrected visual acuity. These days, with the femtosecond platform, suction break, although still a bugbear when it occurs, can usually be tackled during the same sitting by repeating the docking and applanation process and adjusting the laser parameters. When handled properly, perfect flaps can still be created, and there is usually no effect on the eventual visual outcome. Lower pressure femtosecond systems like the VisuMax (Carl Zeiss Meditec, Dublin, Calif., USA/Jena, Germany) tend to have a higher incidence of suction breaks compared to the higher pressure systems like the IntraLase. However, crucial points in avoiding suction breaks with any system are still careful patient selection and good technique. Eyes prone to suction breaks include patients with small, tight palpebral apertures, fidgety, anxious patients with strong Bell’s phenomenon, and the teary eye. Identifying these patients before surgery, preempting the potential problems, and taking precautionary measures like keeping the eye dry before applanation are crucial in preventing the occurrence of suction breaks. Giving proper instructions to the patients, walking them through the procedure and constantly reassuring them during the surgery are important in enhancing patient cooperation. Haze, once thought to be an issue unique to surface ablation procedures like PRK, LASEK and EpiLASIK, has found its way into femtosecond LASIK, occurring in LASIK when flaps of 90 microns or less are created. Haze formation is due to inadvertent breakthrough of Bowman’s layer and the epithelial basement membrane. I routinely perform epithelial thickness measurements in eyes requiring ultra-thin flap LASIK, and if the epithelial thickness is more than 60 to 70 microns, ultra-thin flaps are avoided. Despite these issues, I would not trade my femtosecond laser for the microkeratome. Better flap thickness predictability, more stable, adherent flaps, pristine stromal beds and less incidence of devastating intraoperative flap complications are enough reasons for me to continue using the femtosecond laser for LASIK flap creation. Editors’ note: Dr. Chan has no financial interests related to her comments. Views from Asia-Pacific WANG Zheng, MD Professor of Ophthalmology, Zhongshan Ophthalmic Center 54 Xianlie South Road, Guangzhou 510060, China Tel. no. +86-1390-300-2594 gzstwang@gmail.com T he femtosecond laser has gained more and more popularity among surgeons and patients. Nobody doubts that the femtosecond laser is safer than mechanical microkeratome. The enhanced safety has means two things: less likelihood of complications and less severe consequences if complications do occur. Suction loss during LASIK sometimes happens and is associated with surgeon’s technique, patient’s cooperation, and the design of the microkeratome or femtosecond laser. It is a serious problem when a microkeratome is used. The operation usually has to be aborted. However, it is much easier to handle and the consequence is much less severe if a femtosecond laser is used. As Dr. Waring’s study shows, the surgery may continue by a recut and most of the patients have good refractive and visual outcomes. However, things can be more complicated. I have had a weird case in which the suction was lost twice as the laser scanned to the same location. The third pass was successful. After the flap was lifted, the stromal bed looked smooth as usual with no irregularity either on the bed or on the back of the flap. The remaining part of the surgery was uneventful. After operation, this patient complained of double vision in that eye. The topography showed that the keratoscope mires became distorted at the location where the laser scanning was stopped. The reason for this remains unclear. I agree that the corneal haze mentioned in the article is not necessarily directly associated with the femtosecond laser. It is rather more related to ultra-thin flaps. Before the femtosecond laser era, this kind of haze would also be seen if a very thin flap was created, e.g., using a flawed or re-used blade. Surgeons now tend to make thinner flaps because of the fear of ectasia. So they should be aware of the increased risk of this complication. In addition to the variability in epithelial thickness, the variance in the patient interface of the femtosecond laser is larger than most surgeons think it to be. The error of the size of the cone, for example, may lead to an overly thin or overly thick flap. Some state-of-the-art lasers have incorporated an automatic calibration process for each cone during surgery. This is a great feature to add precision and accuracy to the flap thickness. Editors’ note: Prof. Wang is a consultant for Abbott Medical Optics and Technolas Perfect Vision (Munich, Germany). continued on page 38