RESUMO
PURPOSE: To determine the effectiveness of the correction of corneal astigmatism utilizing the Alcon Image Guidance system (Ft. Worth, Texas) versus manual marking in the orientation of femtosecond laser-assisted astigmatic keratotomy incisions. SETTING: This study was based in a private practice in Albany, New York, USA. DESIGN: Retrospective review of patients undergoing FLACS from January 2018 to June 2022. METHODS: Patients who underwent FLACS with Image Guidance (IG) and without IG were investigated. Variables including pre-operative K values, cylinder, spherical equivalent (SE), and visual acuity (VA) were collected, as well as the cyclorotation angle delta registered by IG, post- operative refractive cylinder, SE, and VA. The primary outcome was post-operative refractive cylinder in patients with IG compared to those without IG. RESULTS: A total of 160 eyes were included, with 103 eyes who had IG and 57 eyes who did not have IG. Post-operative cylinder was similar in those with IG (0.31 +/- 0.36 D) compared to those without IG (0.31 +/- 0.37 D) (p=0.97). Average cyclorotation in the IG group was 2.82 ± 3.03 degrees. When cyclorotation was stratified into three groups (<2.8 degrees, 2.8-8.5 degrees, >8.5 degrees), no differences were found in post-operative refractive cylinder (p=0.35). CONCLUSIONS: Patients who underwent FLACS with Image Guidance had similar post-operative cylinder outcomes compared to those without Image Guidance. This study suggests that the accommodation of cyclotorsion using an advanced image guidance system is similar to that obtained with manual marking techniques in patients having 2 diopters or less of astigmatism corrected.
RESUMO
We have carried out parallel tempering Monte Carlo calculations on the binary six-atom mixed Lennard-Jones clusters, Ar(n)Xe(6-n) (n=0,1,2). We have looked at the classical configurational heat capacity C(V)(T) as a probe of phase behavior. All three clusters show a feature in the heat capacity in the region of 15-20 K. The Ar(2)Xe(4) cluster exhibits a further peak in the heat capacity near 7 K. We have also investigated dynamical properties of the Ar(2)Xe(4) cluster as a function of temperature using molecular dynamics. We report the interbasin isomerization rate and the bond fluctuation parameter obtained from these calculations. At 7 K, the isomerization rate is on the order of 0.01 ns(-1); at 20 K, the isomerization rate is greater than 10 ns(-1). Furthermore, at 7 K, the bond fluctuation parameter is less than 3%; at 20 K, it is in the range of 10-15% (depending on the sampling time used). Using this information, together with Monte Carlo quenching data, we assign the 15-20 K feature in the heat capacity to a solid-liquid phase change and the 7-K peak to a solid-solid phase change. We believe this is the smallest Lennard-Jones cluster system yet shown to exhibit solid-solid phase change behavior.