Changes in crystalline lens parameters during accommodation evaluated using swept source anterior segment optical coherence tomography

Backgrounds:To assess changes in anterior segment biometry during accommodation using a swept source anterior segment optical coherence tomography(SS-OCT).Methods:One hundred-forty participants were consecutively recruited in the current study.Each participant underwent SS-OCT scanning at 0 and−3 diopter(D)accommodative stress after refractive compensation,and ocular parameters including anterior chamber depth(ACD),anterior and posterior lens curvature,lens thickness(LT)and lens diameter were recorded.Anterior segment length(ASL)was defined as ACD plus LT.Lens central point(LCP)was defined as ACD plus half of the LT.The accommodative response was calculated as changes in total optical power during accommodation.Results:Compared to non-accommodative status,ACD(2.952±0.402 vs.2.904±0.382 mm,P<0.001),anterior(10.771±1.801 vs.10.086±1.571 mm,P<0.001)and posterior lens curvature(5.894±0.435 vs.5.767±0.420 mm,P<0.001),lens diameter(9.829±0.338 vs.9.695±0.358 mm,P<0.001)and LCP(4.925±0.274 vs.4.900±0.259 mm,P=0.010)tended to decreased and LT thickened(9.829±0.338 vs.9.695±0.358 mm,P<0.001),while ASL(6.903±0.279 vs.6.898±0.268 mm,P=0.568)did not change significantly during accommodation.Younger age(β=0.029,95%CI:0.020 to 0.038,P<0.001)and larger anterior lens curvature(β=−0.071,95%CI:−0.138 to−0.003,P=0.040)were associated with accommodation induced greater steeping amplitude of anterior lens curvature.The optical eye power at 0 and−3 D accommodative stress was 62.486±2.284 and 63.274±2.290 D,respectively(P<0.001).Age was an independent factor of accommodative response(β=−0.027,95%CI:−0.038 to−0.016,P<0.001).Conclusions:During−3 D accommodative stress,the anterior and posterior lens curvature steepened,followed by thickened LT,fronted LCP and shallowed ACD.The accommodative response of−3 D stimulus is age-dependent.

Combining optical and X-ray observations of galaxy clusters to constrain cosmological parameters

Galaxy clusters present unique advantages for cosmological study.Here we collect a new sample of 10 lensing galaxy clusters with X-ray observations to constrain cosmological parameters.The redshifts of the lensing clusters lie between 0.1 and 0.6,and the redshift range of their arcs is from 0.4 to 4.9.These clusters are selected carefully from strong gravitational lensing systems which have both X-ray satellite observations and optical giant luminous arcs with known redshifts.Giant arcs usually appear in the central region of clusters,where mass can be traced with luminosity quite well.Based on gravitational lensing theory and a cluster mass distribution model,we can derive a ratio using two angular diameter distances.One is the distance between lensing sources and the other is that between the deflector and the source. Since angular diameter distance relies heavily on cosmological geometry,we can use these ratios to constrain cosmological models.Moreover,X-ray gas fractions of galaxy clusters can also be a cosmological probe.Because there are a dozen parameters to be fitted,we introduce a new analytic algorithm,Powell＇s UOBYQA（Unconstrained Optimization By Quadratic Approximation） ,to accelerate our calculation.Our result demonstrates that this algorithm is an effective fitting method for such a continuous multi-parameter constraint.We find an interesting fact that these two approaches are separately sensitive toΩΛandΩM.By combining them,we can get reasonable fitting values of basic cosmological parameters：ΩM=0.26 ＋0.04 -0.04,andΩΛ=0.82 ＋0.14 -0.16.

The Amplitude of Mass Fluctuations and Mass Density of the Universe Constrained by Strong Gravitational Lensing

We investigate the linear amplitude of mass fluctuations in the universe, σ8, and the present mass density parameter of the Universe, Ωm, from statistical strong gravitational lensing. We use the two population model of lens halos with fixed cooling mass scale Mc = 3×1013h-1M⊙ to match the observed lensing probabilities, and leave σ8 orΩm as a free parameter to be constrained by the data. Another varying parameter, the equation of state of dark energy ω, and its typical values of -1, -2/3, -1/2 and -1/3 are investigated. We find that σ8 is degenerate with Ωm in a way similar to that suggested by present day cluster abundance as well as cosmic shear lensing measurements: σ8Ω0.6m≈0.33. However, both σ8≤0.7 and Ωm≤0.2 can be safely ruled out, the best fit is when σ8 = 1.0, Ωm = 0.3 and ω= - 1. This result is different from that obtained by Bahcall & Bode, who gave σ8 = 0.98±0.1 and Ωm = 0.17 ±0.05. For σ8 = 1.0, the higher value ofΩm = 0.35 requires ω = -2/3 and Ωm = 0.40 requires ω= -1/2.

Concordance of Kinematics and Lensing of Elliptical Galaxies with WMAP Cosmology

We explore degeneracies in strong lensing model so to make time delay data consistent with the WMAP （Wilkinson Microwave Anisotropy Probe） cosmology. Previous models using a singular isothermal lens often yield a time delay between the observed multiple images too small than the observed value if we ＂hardwire＂ the now widely quoted post-WMAP ＂high＂ value of the Hubble constant （Ho ～71 ± 4km s^-1 Mpc^-1）. Alternatively, the lens density profile （star plus dark matter） is required to be locally steeper than r-2 （isothermal） profile near the Einstein radius （of the order 3 kpc） to fit the time delays; a naive extrapolation of a very steep profile to large radius would imply a lens halo with a scale length of the order only 3 kpc, too compact to be consistent with CDM. We explore more sophisticated, mathematically smooth, positive lens mass density profiles which are consistent with a large halo and the post-WMAP H0. Thanks to the spherical monopole degeneracy, the ＂reshuffling＂ of the mass in a lens model does not affect the quality of the fit to the image positions, amplifications, and image time delays. Even better, unlike the better-known mass sheet degeneracy, the stellar mass-to-light and the H0 value are not affected either. We apply this monopole degeneracy to the quadruple imaged time-delay system PG 1115＋080. Finally we discuss the implications of the time delay data on the newly proposed relativistic MOND theory.