- Journal of Refractive Surgery
- February 2011 - Volume 27 · Issue 2: 135-146
To evaluate the effective optical zone (the part of the ablation that receives full correction) among eyes that underwent laser epithelial keratomileusis (LASEK)/epi-LASEK treatments for myopic astigmatism.
Twenty LASEK/epi-LASEK treatments with a mean spherical equivalent refraction (SE) of −5.49±2.35 diopters (D) performed using the SCHWIND AMARIS system were retrospectively evaluated at 6-month follow-up. In all cases, pre- and postoperative corneal wavefront analyses were performed with the Keratron Scout (OPTIKON 2000). Effective optical zone values were evaluated from the changes of root-mean-square (RMS) of higher order wavefront aberration (ΔRMSho), spherical aberration (ΔSphAb), and RMS of the change of higher order wavefront aberration (RMS[ΔHOAb]). Correlations of effective optical zone with planned optical zone and SE correction were analyzed using a bilinear function as well as calculations of the isometric lines for which effective optical zone equals planned optical zone and of the nomogram planned optical zone to achieve an intended effective optical zone.
At 6 months, SE was −0.05±0.43 D, with 90% of eyes within ±0.50 D. Mean higher order wavefront aberration RMS increased 0.12 μm, spherical aberration 0.09 μm, and coma 0.04 μm after treatment (6-mm diameter). Mean planned optical zone was 6.76±0.25 mm, whereas mean EOZΔRMSho was 6.74±0.66 mm (bilinear correlation P<.005), EOZΔSphAb was 6.83±0.58 mm (bilinear correlation P<.0001), and EOZRMS(ΔHOAb) was 6.42±0.58 mm (significantly smaller, P<.05; bilinear correlation P<.0005).
The EOZΔRMSho and EOZΔSphAb were similar to the planned optical zone, whereas EOZRMS(ΔHOAb) was significantly smaller. Differences between effective optical zone and planned optical zone were larger for smaller planned optical zone or larger SE corrections. Planned optical zones >6.75 mm result in effective optical zones at least as large as planned optical zones. For optical zones <6.75 mm, a nomogram should be applied.
From SEKAL Rovigo Microsurgery Centre, Rovigo, Italy (Camellin); Grupo de Investigación de Cirugía Refractiva y Calidad de Visión, Instituto de Oftalmobiología Aplicada, University of Valladolid, Valladolid, Spain (Arba Mosquera); and SCHWIND eye-tech-solutions, Kleinostheim, Germany (Arba Mosquera).
Mr Arba Mosquera is an employee of SCHWIND eye-tech-solutions, Kleinostheim, Germany. Dr Camellin has no proprietary interest in the materials presented herein.
Correspondence: Massimo Camellin, MD, SEKAL Rovigo Microsurgery Centre, Via Jean Henri Dunant, 45100 Rovigo, Italy. E-mail: email@example.com
Received: July 20, 2009
Accepted: April 08, 2010
Posted Online: May 03, 2010