ABSTRACT
A coherent x-ray diffraction experiment was performed on an isolated colloidal crystal grain at the coherence beamline P10 at PETRA III. Using azimuthal rotation scans the three-dimensional (3D) scattered intensity from the sample in the far-field was measured. It includes several Bragg peaks as well as the coherent interference around these peaks. The analysis of the scattered intensity reveals the presence of plane defects in a single grain of the colloidal sample. We confirm these findings by model simulations. In these simulations we also analyze the experimental conditions required to phase the 3D diffraction pattern from a single colloidal grain. This approach has the potential to produce a high resolution image of the sample revealing its inner structure, with possible structural defects.
ABSTRACT
PURPOSE: To compare and evaluate postoperative results of two methods of refractive laser surgery, Epi-LASIK and LASEK, performed at the Department of Ophthalmology and Optometry of St. Anne's University Hospital Brno, Czech Republic. METHODS: 128 eyes operation were performed on patients with myopia, 102 with the Epi-LASIK method and 26 with the LASEK method. The preoperative mean spherical equivalent was -4.8 +/- 2.6 D (range -2.3 to -7.5) in the Epi-LASIK eyes and -3.5 +/- 3.1 D (range -1.6 to -7.8) in the LASEK eyes. The average preoperative uncorrected visual acuity (UCVA) was 0,129 (from 0.02 to 0.8) with the Epi-LASIK method and 0,246 (from 0.02 to 0.8) with the LASEK method. The best average corrected visual acuity was 1,139 (from 0.63 to 1.6) with the Epi-LASIK method and 1.115 (from 0.25 to 1.25) with the LASEK method. The average cylindrical refraction of the Epi-LASIK patients before the operation was -1.52 +/- 0.80 D (range -1.0 to -3.5) and the LASEK patients was -1.55 +/- 0.89 D (range -1.0 to -3.0), except of those who have astigmatism up to +/- 0.75D. In both methods was used the excimer laser Mel 80 Meditec-Zeiss with 193 nm wavelength and the frequency of 250 Hz and active eye-tracking system. RESULTS: The postoperative mean spherical equivalent was 0 +/- 0.5 D (range -0.6 to 0.6) in the Epi-LASIK eyes and 0.3 +/- 0.4 D (range -0.3 to 0.7) in the LASEK eyes. The average uncorrected visual acuity was 0.745 with Epi-LASIK and 0.687 with LASEK after first week, 0.996 and 1,083 after month, 1.068 and 1.063 after 3 months, 1.147 and 1,082 after 6 months, 1.090 and 1.031 after one year. The average cylindrical refraction after the operation was -0.82 +/- 0.69 D (range 0 to -1.7) with Epi-LASIK and -0.59 +/- 0.55 D (range 0 to -1.5) with LASEK. Average "haze", evaluated by the Gartry's scale, was 0.39 with Epi-LASIK and 0.46 with LASEK after week, 0.21 and 0.06 after one year. CONCLUSIONS: The Epi-LASIK and LASEK methods have comparable postoperative results of visual acuity, astigmatism, "haze". They are effective too in worse form of the myopia.
