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Pablo Perez-Merino, Miriam Velasco-Ocana, Eduardo Martinez-Enriquez, Susana Marcos; OCT-based crystalline lens topography in accommodating eyes. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3565.
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© ARVO (1962-2015); The Authors (2016-present)
To measure anterior and posterior crystalline lens topography in accommodating eyes. To evaluate the relationship between anterior and posterior lens surface shape, cornea and lens shape, and their changes with accommodation.
Custom spectral-domain optical coherence tomography (SD-OCT) provided with automatic quantification and distortion correction algorithms was used to characterize three-dimensionally and in vivo the human crystalline lens in 4 subjects (7 eyes; 31±3 y.o), for accommodative demands between 0 to 6 D, in 1.5 D steps. Anterior segment (cornea and lens) surfaces were fitted to 6th order Zernike polynomials to quantify geometry and biometry (anterior chamber depth (ACD), lens thickness, and corneal and lens radii). Corneal and lens surface elevations were analyzed by means of RMS (high order aberrations (HOAs), astigmatism, coma, trefoil and spherical).
Anterior and posterior radii of curvature decreased at rates of 0.61±0.15 and 0.15±0.06 mm/D, ACD decreased 0.04±0.01 mm/D and lens thickness increased 0.05±0.01 mm/D with accommodation demand. Astigmatism was the predominant lens surface aberration (69%-anterior; 56%-posterior). The RMS of HOAs of the posterior lens surface was statistically significant higher than the anterior surface (x2.92; p<0.05). The dominant HOAs of the posterior lens surface were Z33, Z40 and Z42 (accounting for 12%, 14% and 16% of the variance). Astigmatism, coma and trefoil changed with accommodation by a factor of x1.1, x1.3 and x1.4 respectively in both lens surfaces. Spherical aberration showed higher changes with accommodation in the anterior lens surface (x2.5 vs x1.15). The astigmatic angle showed high degree of alignment among corneal and anterior lens surfaces (<13 deg). However, the angle between anterior and posterior lens astigmatism differed by 26 deg. In general, there was slight correlation but not significant between HOAs terms of the anterior and posterior lens surfaces (r=0.38, un-accommodated; r=0.52, 6D accommodation).<br /> Fig. 1. 3D full anterior segment image and lens surface elevation maps for S#1(OS).
OCT provided with distortion correction is an excellent instrument for evaluating the crystalline lens changes in shape and surface produced by accommodation and for exploring the role of the crystalline lens in the eye's optics. The increased high order aberrations of the posterior lens surface might be associated to the zonular tension.
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