Multifocal vision corrections are increasingly used solutions for presbyopia. In the current study we have evaluated, optically and psychophysically, the quality provided by multizone radial and angular segmented phase designs. Optical and relative visual quality were evaluated using 8 subjects, testing 6 phase designs. Optical quality was evaluated by means of Visual Strehl-based-metrics (VS). The relative visual quality across designs was obtained through a psychophysical paradigm in which images viewed through 210 pairs of phase patterns were perceptually judged. A custom-developed Adaptive Optics (AO) system, including a Hartmann-Shack sensor and an electromagnetic deformable mirror, to measure and correct the eye's aberrations, and a phase-only reflective Spatial Light Modulator, to simulate the phase designs, was developed for this study. The multizone segmented phase designs had 2-4 zones of progressive power (0 to +3D) in either radial or angular distributions. The response of an "ideal observer" purely responding on optical grounds to the same psychophysical test performed on subjects was calculated from the VS curves, and compared with the relative visual quality results. Optical and psychophysical pattern-comparison tests showed that while 2-zone segmented designs (angular & radial) provided better performance for far and near vision, 3-and 4-zone segmented angular designs performed better for intermediate vision. AO-correction of natural aberrations of the subjects modified the response for the different subjects but general trends remained. The differences in perceived quality across the different multifocal patterns are, in a large extent, explained by optical factors. AO is an excellent tool to simulate multifocal refractions before they are manufactured or delivered to the patient, and to assess the effects of the native optics to their performance.
It has been reported that intake of (n-3) polyunsaturated fatty acids (PUFA) reduces the risk of coronary heart disease and decreases biliary cholesterol saturation in the bile of gallstone patients. We investigated the effect of n-3 PUFA on cholesterol saturation index (CSI) and nucleation time (NT) in obese subjects who were losing weight. This was a double-blind, placebo-controlled clinical trial. Obese women (n = 35) with a body mass index (BMI) > or = 30 kg/m(2), with no prior history of gallstones or cholecystectomy by ultrasound were first studied to ensure absence of stones or biliary sludge. The women were then assigned to a hypocaloric regimen [5.02 MJ (1200 kcal)/d] and to receive 1200 mg/d of ursodeoxycholic acid (UDCA), 11.3 g/d of (n-3) PUFA or a placebo for 6 wk. BMI, CSI and NT were recorded at baseline and at the end of the experimental period. BMI decreased 5.75 +/- 2.7%/mo (range, 1.5-12.42%/mo) during the experiment. The CSI did not change in any of the groups. Cholesterol NT decreased significantly in the UDCA and placebo groups, but not in the (n-3) PUFA group. None of the women had developed gallstones at 6 wk. These results suggest that (n-3) PUFA maintain the CSI and NT in obese women during rapid weight loss, which probably results in the prevention of cholesterol gallstone formation.
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