Wavelight ex500

As already mentioned, the algorithm for the computation of the ablation profile is proprietary of the manufacturing company and cannot be accessed. The user manual of the excimer laser Wavelight EX500 by Alcon describes the different ablation options, available to be used by the surgeon, by presenting multiple examples. The most used treatment is the wavefront-optimized or “standard” treatment for the calculation of the ablation map, where the user is required to insert the target refraction and the laser's software establishes the ablation profile. This kind of treatment is not patient specific: the software will propose the same ablation map for patients with the equal refraction, disregarding individual characteristics. As it can be seen in the treatment plan of a patient who received this treatment, the ablation map shows a pattern that follows an aspheric shape. The ablation profile shown in the treatment plan of the patient was reproduced by using a biconic (Equation 2) and by enforcing the same central ablation depth as the one of the real treatment. The standard or wavefront-optimized treatment must not be confused with the wavefront-guided treatment or customized treatment, which uses corneal wavefront aberrations to determine the customized ablation profile needed to correct patient's visual acuity in a personalized fashion.

All surgeries were performed by 2 surgeons (T.-Y.C. and D.H.L.) using standardized techniques. Eligible patients were scheduled to undergo bilateral PRK surgery using a WaveLight EX500 excimer laser (Alcon). The correction target was based on the manifest refraction adjusted using the Alcon nomogram, with emmetropia being the target in all patients. A few drops of 20% alcohol were instilled into an 8.0-mm well to create a round epithelial defect. After 25 seconds, the alcohol was removed, and a balanced salt solution was poured to irrigate the cornea. The epithelium was then removed smoothly using a spatula, and laser ablation was performed. The eyes were once again irrigated with a balanced salt solution. Sponges soaked in 0.05% mitomycin-C solution were placed on the eye for 20 seconds, followed by vigorous irrigation with a balanced salt solution. Finally, an AcuVue Oasys (Johnson and Johnson) bandage contact lens was placed on the eye. The same procedure was repeated in the other eye.

Enhancement was performed via alcohol-assisted PRK. Epithelial debridement was performed with 18% alcohol for 25 seconds, followed by stromal ablation with a WaveLight EX500 excimer laser (Alcon Laboratories, Inc., Fort Worth, Texas, USA). Laser settings included an ablation zone of 6.5 mm and a transitional zone of up to 9.0 mm. Mitomycin C 0.02% was applied for 20 seconds whenever ablation depth exceeded 65 microns. After the procedure, a bandage contact lens was placed for one week. Post-operative regimen included topical moxifloxacin 0.5% four times daily for one week and prednisolone acetate 1% four times daily for one month. After one month, prednisolone acetate was replaced with fluorometholone 0.1% four times daily, which was then tapered until 12 weeks post-operative.

All patients underwent wavefront optimized laser refractive surgery, PRK in 50 eyes and LASIK in 106 eyes, for correction of simple, myopic, hyperopic or mixed astigmatism, applying WaveLight EX500 (Alcon Laboratories; Ft Worth, TX, USA). All surgeries were performed by a single surgeon, the author. A superior hinge was applied in LASIK cases using Moria Evolution 3 Microkeratome (Moria, Antony, France) with a programmed planned flap thickness of 110 μm and a diameter of 8 mm. In PRK, the corneal epithelium was removed in a diameter of 8 mm in a centripetal fashion using a blunt hockey blade. UCVA and manifest refraction were evaluated at 1 month post-operatively. Postoperative refraction was assessed by a TOPCON RM-8900 Auto Refractometer (Topcon Medical Systems, Tokyo, Japan).

Femtosecond laser (FS200, Alcon Laboratories, Inc., USA) was used to create a corneal flap of 110 μm thickness with an 8.00 mm diameter [1 (link)]. Excimer laser (WaveLight EX500, Alcon Laboratories, Inc., USA) was used for the myopic ablation, and the ablation zone diameter was 6.00 to 6.50. After the excimer laser ablation (with the flap folded on itself), Vibex Xtra riboflavin solution containing 0.25% riboflavin (Avedro Inc., USA) was placed on the exposed stromal bed for 90 seconds. Following stromal soaking, the stroma was washed with BBS and the flap was repositioned in place. The cornea was then irradiated with ultraviolet-A (UVA) light (KXL System, Avedro Inc.) with a wavelength of 365 nm and an irradiance of 30 mW/cm² for 90 seconds (total energy 2.7 J/cm²). After irradiation, a bandage contact lens was placed on the corneal surface for pain relief. After surgery, 0.5% lavo-ofloxacin eye drops were applied four times per day for two weeks; 0.1% fluorometholone eye drops were used four times per day for the first week, and then reduced gradually; 0.1% sodium hyaluronate eye drops were used four times per day for four weeks. The bandage contact lens was removed when the corneal epithelium healed.