Geometry of bevelled edge femtosecond laser flaps created with the VisuMax®

Poster Details

First Author: F.Thieltges GERMANY

Co Author(s):    K. Ponto   J. Rosbach   J. Eha   N. Pfeiffer   U. Vossmerbaeumer  

Abstract Details

Purpose:

Femtosecond Laser created flaps have become a gold standard for LASIK procedures. Advantages over microkeratome-flaps include a uniform and minimized flap thickness and a reduced risk of intra- and postoperative complications. Enhanced postoperative stability is ascribed to angulation of the side-cut. The purpose of our study is to analyze the real degree of angulation six months after the procedure using Spectral Domain Optical Coherence Tomography (SD-OCT) and to analyze determinants for the postoperative outcome.

Setting:

Consecutive clinical case series

Methods:

207 eyes of 106 patients (46 male/60 female) were included in the study. Inclusion criteria were a myopic refraction of max. –9.00 dpt, hyperopia of max +6.25 dpt and corneal astigmatism <5.5 dpt. All patients were treated with a FemtoLASIK using a VisuMax® femtosecond laser (Carl Zeiss Meditec, Jena, Germany) and a MEL80® (Carl Zeiss Meditec, Jena, Germany). All surgeries were performed by the same surgeon (UV). At six months follow-up, the flap was assessed using spectral-domain OCT (SD-OCT, RTVue). The geometry of the angulated side-cut and the flap were measured using proprietary software of the device at 2 points. Correlations to the intended geometry, pre- and postoperative refraction and corneal thickness were calculated using Excel® (Microsoft Corp., Seattle, WA) and SPSS® (SPSS, Chicago, IL) software.

Results:

Mean preoperative myopic refraction was -3.69±2.15 dpt SE, mean hyperopic refraction was 2.92±1.43 dpt. Flaps were programmed with a 60° inward beveled sidecut at a thickness of 120 and 100 µm. Mean sidecut angulation as measured by SD-OCT was 44.93±8.19° (range 31.54-67.60) for the total cohort, 46.09±8.25° in the myopic group, 43.41±1.61° in the hyperopic group. There was no statistically significant correlation between cleavage precision to preoperative refraction or corneal thickness for either subgroup.

Conclusions:

Six months after surgery, the distinctive beveled-edge geometry of the flap was clearly recognizable in OCT measurements. Analysis of the angle demonstrated an acceptable geometrical congruence between programmed flap shape and the real outcome. FINANCIAL DISCLOSURE?: No