Torsional Group Research Articles

The Comparison between Torsional and Conventional Mode Phacoemulsification in Moderate and Hard Cataracts

PurposeTo compare the intraoperative performances and postoperative outcomes of cataract surgery performed with longitudinal phacoemulsification and torsional phacoemulsification in moderate and hard cataracts.MethodsOf 85 patients who had senile cataracts, 102 eyes were operated on using the Infiniti Vision System. Preoperative examinations (slit lamp examination, mean central corneal thickness, and central endothelial cell counts) were performed for each patient. Cataracts were subdivided into moderate and hard, according to the Lens Opacities Classification System III grading of nucleus opalescence (NO). Eyes in each cataract group were randomly assigned to conventional and torsional phaco-mode. Intraoperative parameters, including ultrasound time (UST), cumulative dissipated energy (CDE), and the balanced salt solution plus (BSSP) volume utilized were evaluated. Best corrected visual acuity (BCVA) was checked on postoperative day 30; mean central corneal thickness and central endothelial cell counts were investigated on postoperative days 7 and 30.ResultsPreoperative BCVA and mean grading of NO showed no difference in both groups. Preoperative endothelial cell count and central corneal thickness also showed no significant difference in both groups. In the moderate cataract group, the CDE, UST, and BSSP volume were significantly lower in the torsional mode than the longitudinal mode, but they did not show any difference in the hard cataract group. Torsional group showed less endothelial cell loss and central corneal thickening at postoperative day seven in moderate cataracts but showed no significant differences, as compared with the longitudinal group, by postoperative day 30.ConclusionsTorsional phacoemulsification showed superior efficiency for moderate cataracts, as compared with longitudinal phacoemulsification, in the early postoperative stage.

Torsional ultrasound modality for hard nucleus phacoemulsification cataract extraction

Aim:To evaluate the efficacy and safety of phacoemulsification using torsional modality with different parameter settings for hard nucleus cataract extraction.Design:A prospective, randomised clinical study.Methods:A clinical practice study conducted at the...

Torsional mode versus conventional ultrasound mode phacoemulsification: Randomized comparative clinical study

To compare the intraoperative and short-term postoperative outcomes of cataract surgery performed with torsional mode and conventional ultrasound mode using the Infiniti Vision System (Alcon Laboratories). Cataract Service, Zhongshan Ophthalmic Center, Sun-Yat-Sen University, Guangzhou, China. In this randomized comparative study, 525 eyes were assigned to phacoemulsification by torsional mode or conventional ultrasound (US) mode. The surgery was performed by an experienced surgeon, and the outcomes were evaluated by an examiner who was masked to treatment assignments. Primary outcome measures were US time (UST), cumulative dissipated energy (CDE), and surgical complications. Patients were seen 1, 7, and 30 days after surgery. Postoperative outcome measures were the final best corrected visual acuity (BCVA) and the change in corneal clarity, central corneal thickness (CCT), and endothelial cell count. The US group had 262 eyes and the torsional group, 263 eyes. All patients completed the follow-up visits. In the eyes with nucleus density grades of 1, 2, 3, and 4, the mean UST was 10.25 seconds +/- 7.4 (SD), 25.14 +/- 5.5 seconds, 36.45 +/- 8.3 seconds, and 61.44 +/- 17.8, respectively, in the US group and 8.32 +/- 6.8 seconds, 18.45 +/- 7.2 seconds, 29.48 +/- 12.4 seconds, and 48.39 +/- 20.3 seconds, respectively, in the torsional group (P<.001); the mean CDE was 1.25 +/- 0.5, 4.18 +/- 1.2, 8.59 +/- 6.5, and 16.51 +/- 9.6, respectively, in the US group and 0.94 +/- 0.3, 3.13 +/- 2.7, 7.47 +/- 12.6, and 14.08 +/- 8.3, respectively, in the torsional group (P<.001). At 1 day and 7 days, the mean BCVA was 0.23 +/- 0.12 logMAR and 0.00 +/- 0.10 logMAR, respectively, in the US group and 0.18 +/- 0.11 logMAR and -0.08 +/- 0.05 logMAR, respectively, in the torsional group (P<.001). At 30 days, the mean BCVA was -0.10 +/- 0.07 logMAR and -0.12 +/- 0.06 logMAR in the US group and the torsional group, respectively (P>.01). At 1 day and 7 days, the mean CCT was 625 +/- 80 microm and 568 +/- 37 microm, respectively, in the US group and 601 +/- 35 microm and 559 +/- 40 microm, respectively, in the torsional group (P<.001). At 30 days, the mean CCT was 531 +/- 30 microm in the US group and 529 +/- 39 microm in the torsional group (P>.01). At 7 days and 30 days, the mean central corneal endothelial cell count was 2135 +/- 858 cells/mm(2) and 2084 +/- 527 cells/mm(2), respectively, in the US group and 2004 +/- 656 cells/mm(2) and 1953 +/- 615 cells/mm(2), respectively, in the torsional group (P<.001). The torsional mode may provide more effective lens removal with a lower level of phacoemulsification time and energy.

Intramolecular Hydrogen Bonding in Disubstituted Ethanes: General Considerations and Methodology in Quantum Mechanical Calculations of the Conformational Equilibria of Succinamate Monoanion

The importance of intramolecular hydrogen bonding between the carboxylate oxygen and amide proton of succinamate anion has been investigated by quantum mechanical simulations as a function of solvent for comparison with conformational equilibria estimated by NMR spectroscopy. The focus is on those methodological considerations of general interest to the conformational equilibrium problem, which are also particularly relevant to the quantum calculations. The roughly planar symmetry of the amide and carboxylate substituents of succinamate anion and the possibility of intramolecular hydrogen-bond formation together suggest that the orientational degrees of freedom of the substituents could play an important role in the equilibrium of the CH2-CH2 torsion. To test this hypothesis, two-dimensional potential-energy surfaces (PESs) were mapped out from the quantum mechanical calculations, with coordinates corresponding to the CH2-CH2 torsional and amide group rotational degrees of freedom. The Boltzmann populations obtained from two-dimensional PESs and those obtained from a one-dimensional adiabatic surface for the CH2-CH2 torsion were compared with the experimental results. In these comparisons, the agreement of calculated gauche fractions with corresponding experimental values was checked, as well as the agreement between predicted coupling constants and those determined from experimental spectra. In polar protic and aprotic solvents, where highly polar trans conformations can be stabilized by dipole-dipole and hydrogen-bonding interactions with the solvent, the orientational degree of freedom of the amide substituent appears to play a sufficiently important role in the CH2-CH2 torsional equilibrium that it cannot be safely ignored in the simulations.

Numerical modeling and interpretation of drillstring waves

Drill‐bit seismic and pilot seismograms contain drillstring periodicities from signal and environmental noise sources. These coherent components are similar in seismic‐while‐drilling correlations, and their joint contribution may cause distortions in signal processing. Numeric modeling of the drillstring transmission line is used to correctly interpret the axial and torsional events with similar propagating modes of signal and noise. The reflection coefficients are computed for drillstrings of arbitrary materials, and their average mechanical features are related to the axial and torsional group velocities obtained by the dispersion equations. Fitting of the periodical components in the real seismograms is used to automatically correct the drill‐bit pilot delays and to estimate the surface and downhole boundary conditions.