Comparison of lens thickness measurements using the anterior segment optical coherence tomography and A-scan ultrasonography.

PURPOSE: To assess lens thickness (LT) measurements with anterior segment optical coherence tomography (AS-OCT) in comparison with A-scan ultrasonography (A-scan US). METHODS: Enrolled were 66 eyes of 48 phakic elderly volunteers aged > or = 50 years and 56 eyes of 56 young participants aged 18 to 40 years. LT was measured with the internal manual caliper tools in AS-OCT. The A-scan US measurements were based on an average of 10 consecutive automatic measurements. Reproducibility was assessed by three measurements each with AS-OCT and A-scan US independently obtained by two observers who were masked to one another's results. RESULTS: The failure rates of AS-OCT and A-scan US were 9.1% and 7.6%, respectively, in elderly subjects, but no failure was observed in young subjects. The LT values measured by AS-OCT were significantly greater than A-scan US; the paired difference was 0.135 mm in elderly and 0.101 mm in young subjects (P < 0.001). These differences did not correlate with the nuclear cataract grades (r = 0.078, P = 0.558). Intraobserver agreement on AS-OCT (95% limits of agreement [LoA]: -0.049 to +0.045 mm; ICC: 0.999) was better than A-scan US (95%LoA: -0.194 to +0.218 mm; ICC: 0.974). The 95% LoA of interobserver agreement using AS-OCT and A-scan were -0.084 to +0.073 and -0.278 to +0.239 mm, respectively, and the ICCs were 0.996 and 0.960, respectively. CONCLUSIONS: AS-OCT can be used to measure lens thickness in most eyes with clear or opacified lenses. It appears to be an alternative means of measuring lens thickness, particularly when a noncontact method is needed.

On the source of organic acid aerosol layers above clouds.

During the July 2005 Marine Stratus/Stratocumulus Experiment (MASE) and the August-September 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS), the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter probed aerosols and cumulus clouds in the eastern Pacific Ocean off the coast of northern California and in southeastern Texas, respectively. An on-board particle-into-liquid sampler (PILS) quantified inorganic and organic acid species with < or = 5-min time resolution. Ubiquitous organic aerosol layers above cloud with enhanced organic acid levels were observed in both locations. The data suggest that aqueous-phase reactions to produce organic acids, mainly oxalic acid, followed by droplet evaporation is a source of elevated organic acid aerosol levels above cloud. Oxalic acid is observed to be produced more efficiently relative to sulfate as the cloud liquid water content increases, corresponding to larger and less acidic droplets. As derived from large eddy simulations of stratocumulus underthe conditions of MASE, both Lagrangian trajectory analysis and diurnal cloudtop evolution provide evidence that a significant fraction of the aerosol mass concentration above cloud can be accounted for by evaporated droplet residual particles. Methanesulfonate data suggest that entrainment of free tropospheric aerosol can also be a source of organic acids above boundary layer clouds.

[A study on axis length measurement of high myopia with cataract].

PURPOSE: To study the accuracy of axis length measurement on high myopia with cataract. METHODS: A/B scan ultrasonography and IOL-master were used to measure the ocular axial length in 168 high myopic eyes with cataract of 103 cases. B-scan ultrasonography was used to examine posterior scleral staphyloma. Refractive results were recorded during the follow-up after operation to evaluate the accuracy of measurement. RESULTS: The rate of posterior scleral staphyloma was 76.19%. The average postoperative error of refractive of all eyes was between -1.0 D and +1.0 D. CONCLUSION: Accurate data of axis length can be obtained by combining results of A-scan, B-scan ultrasonography and IOL-master for high myopia with cataract, especially for patients with posterior scleral staphyloma.