EyeWorld China September 2019 Issue

The Femtosecond Laser Flap: Managing complications Dr. Alnette Lee Tan Table 5: Techniques to manage Incomplete FS Flap 1. Recut with the same parameters ensuring the suction ring is at the exact position of the previous pass. 2. Recut right after with a bigger flap size and a deeper level, ensuring not to cut through the incomplete interface. The canal should be put at a different angle to prevent overlap with the previous canal. Following the dissection of the interface, the circumference of the flap should be scoured with a wider diameter to make sure that the second interface is completed. Patient selection is the key aspect of femtosecond laser. Eyeball movement, loss of suction, incomplete flaps, teary eye and accidental service setting on laser are commonly encountered issues during femtosecond laser. Table 4: Clinical pearls of femtosecond laser • Allows customization of flap thickness • Provides strong flap healing and is less prone to displacement • Allows customization of position of hinging • Enables prediction of flap thickness is possible • Allows individualized flap centration • Useful in different types of keratoplasty • Easily cuts through dense corneal scars (microbial keratitis, Buckler dystrophy) • Minimizes potential intraoperative complications • Provides faster visual and refractive recovery Femtosecond laser is known for its precision, safety, versatility and patient comfort. Wide adjustment range of geometries and parameters, ability to create thinner and custom flaps and faster visual and refractive recovery are some the most important advantages of femtosecond laser. Due to its ability to create thinner flaps, biomechanical insult following femtosecond laser is believed to be minimal. The role of corneal epithelium in surface abalation Prof Zhai Changbin 9 While FS laser has provided significant improvement toophthalmic refractive surgery, complications such as patient’s eyeball movement, loss of suction, incomplete flaps, teary eye and accidental service settings on the machine can be encountered in routine clinical practice. “Patient selection is the key aspect of FS laser” said Dr. Alnette Tan. In order to achieve suction and secure the applanation cone successfully, the patients need to be able to refrain from moving, jerking, or trying to squeeze eyes shut. “Eyeball movement, especially during the last second of side cut can result in an inadequate inferior side cut,” explained Dr. Tan. Loss of suction midway is another issue. Loss of suction can occur due to loose conjunctiva or due to patient movement during the procedure. It can be avoided by using caution while applying the interface and counseling the patient to stay still and avoid jerky movements. The next common complication during FS surgery is incomplete FS flaps. Dr. Tan suggests that there are 3 ways of dealing with this complication (Table 5). Dr. Tan explained that FS200 has a unique way of managing opaque bubble layer (OBL). By creating a tunnel to vent gas created during flap creation, the Wavelength ® FS200 femtosecond laser minimizes OBL issues, the excimer laser treatment can be performed right after the flap is cut resulting in fast total refractive procedures. Examination of the field and drying the areas of teary eye before applying the suction ring is an important step while performing FS laser. “Drying thefluidand re-docking and sweeping away any loose or redundant conjunctiva.” added Dr. Tan as an important step to avoid complications. “Corneal wound healing reaction is one of the main determinants of surgical effectiveness and safety. The integrity of the corneal epithelium is necessary to maintain the balance between the epithelium and the stroma. In refractive surgery the integrity and vitality of corneal epithelium is important for the good healing of corneal wounds, avoiding complications and obtaining the best postoperative vision.” - Prof. Zhai Changbin