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Issue link: https://daily.eyeworld.org/i/124062
50 EW SHOW DAILY Sunday, April 21, 2013 Meeting Reporter Studies show astounding accuracy in femtosecond flap creation by Enette Ngoei EyeWorld Contributing Writer J ohn Kanellopoulos, MD, New York, described a novel model of digitized clinical validation of femtosecond LASIK flap parameters and opaque bubble layer (OBL) occurrence at a scientific paper session on keratorefractive LASIK. The study included 139 consecutive myopic and hyperopic LASIK patients who were treated with the Wavelight 500Hz excimer and the FS200 femtosecond lasers (Alcon, Fort Worth, Texas), Dr. Kanellopoulos said. Perioperative refractive error, visual acuity, keratometric, topographic flap dimensions, and OBL were evaluated preop as well as postop. This was done utilizing a proprietary macro procedure on a commercially available image processing software: The flap creation report image provided by the FS200 femtosecond laser was analyzed digitally and calibrated on a scale converting pixels to mm, he said. Similarly, OBL occurrence was measured as a percentage of the ac- tual flap surface area. The mean follow-up time was 25 months (21-37). Results of the study showed that for the 206 myopic flaps, the intended diameter was 8 mm and the achieved 7.95 mm (+/–0.12). For the 52 hyperopic flaps, the intended diameter was 9.5 mm and the achieved 9.52 mm (+/–0.08). Dr. Kanellopoulos said that 60% of patients had no OBL, 35% had under 2% surface area OBL, and 5% had up to 20% of surface OBL. He said that this novel validation model is very easy to perform and confirms the high reproducibility in flap parameters and small occurrence of OBL in both myopic and hyperopic LASIK cases with this femtosecond laser. The study indicates an astounding accuracy (less than –0.12 mm, up to +0.06 mm) on the flap creation with the FS200 femtosecond laser, he said. Flap precision was outstanding in all groups with the most precise flaps being those intended for 9.5 mm (+/–0.00 mm to +/–0.04 mm for the horizontal and vertical meridian). Karolinne M. Rocha, MD, Cleveland, presented an "Anterior Segment Spectral Domain OCT Analysis of Prospective Randomized Contralateral Femto LASIK Study for Myopia." The prospective study compared femto LASIK flap architecture, epithelial thickness profile and clinical outcomes after flap creation with the IntraLase FS60 (Abbott Medical Optics, Santa Ana, Calif.) in one eye and WaveLight FS200 in the fellow eye using a spectral domain OCT, she said. Thirty-six myopic eyes underwent femto LASIK. Flap thickness was 110 microns and the diameter was 8.7 mm. Clinical outcomes were measured at one week, one month, and nine months postop. Dr. Rocha said that the results of the study showed the FS200 and IntraLase femtosecond lasers are both accurate and reproducible for the creation of LASIK flaps. No signifi- cant differences were observed in visual acuity, spherical equivalent, coma and spherical aberration. Rainbow glare and increased light scattering (C-Quant) were observed to be significant at one week postop with improvement at three months, she said. The FS200 flaps were slightly thinner and significant differences were observed centrally (p=0.039) and superiorly (p=0.032) at three months postop. Significant epithelial and femto LASIK flap thickening were observed at three months after femto LASIK for myopia along with mild myopic regression. Finally, Dr. Rocha said that epithelial remodeling may play a role in early refractive instability after LASIK. EW Editors' note: Dr. Kanellopoulos has financial interests with Alcon. Dr. Rocha has no related financial interests. The ocular surface unsurfaced by Ellen Stodola EyeWorld Staff Writer Edward J. Holland, MD A session at Cornea Day 2013 highlighting the ocular surface had a number of discussions designed to cater specifically to the cornea specialist. Edward J. Holland, MD, Cincinnati, discussed some of the causes and treatments for limbal stem cell deficiency. Dr. Holland said it is important to know about limbal stem cell deficiency, even if you do not normally take care of these patients. He said that there is generally a good understanding about the limbal epithelial stem cells and that trauma or toxicity to these can cause limbal stem cell deficiency. However, slower, more gradual cases of limbal stem cell deficiency are often harder to recognize. The three main causes he highlighted were traumatic or toxic, inflammatory, and inherited or congenital. Loss of cells from all of these can cause the patient to have a variety of issues, including persistent epithelial defects, corneal scarring and ulceration, and severe visual loss. "We do have a variety of medical treatments that can help the mild to moderate patient," Dr. Holland said. Taking the preservatives out of drops can be beneficial, and nutritional supplements can be good for a patient's tear film. However, he said the solution for patients who have total limbal deficiency may be harder to determine. He sees patients too often who have had multiple corneal transplants. For a patient with total limbal deficiency, he said, the most important thing is to do no harm and not to perform routine keratoplasty on those patients. "I think patients with limbal stem cell deficiency certainly have options now for visual recovery," Dr. Holland said. Clinicians, whether specializing in retina, cornea or glaucoma, need to recognize early clinical findings and prevent progression, he said. Not performing routine keratoplasties on these patients and understanding the options for medical management also come into play when treating limbal stem cell deficiency, he said. EW Editors' note: Dr. Holland has no financial interests related to this talk.