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Mengchan Sun, Judith Birkenfeld, Alberto de Castro, Sergio Ortiz, Pablo Perez, Mirian Velasco, Susana Marcos; OCT 3-D surface topography of isolated human crystalline lenses. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3784.
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© ARVO (1962-2015); The Authors (2016-present)
To measure surface topography of isolated human crystalline lenses, and evaluate the relationship between anterior and posterior lens shapes and their changes with age.
Custom spectral optical coherence tomography (sOCT) was used for 3D imaging of isolated crystalline lenses in 2 orientations (anterior surface/posterior surface up) with 12 x 12 mm range, 0.17/0.007 mm lateral/axial resolution. 23 crystalline lenses from 18 human donor eyes (19 to 71 yr) were extracted <48 h post-mortem and imaged in a DMEM-filled cuvette. Custom algorithms were used for surface segmentation and distortion correction. Anterior and posterior surface elevations were fitted by conics (radius of curvature R and asphericity Q), and (after subtraction of the reference spheres) fitted by 7th order Zernike polynomials in 6-mm pupils. Deviations from a sphere are accounted by the corresponding Zernike terms, Root Mean Square (RMS) and variance. The age-dependence and anterior/posterior correlations of these parameters were evaluated by linear regressions.
Anterior and posterior surfaces of isolated lens became significantly flatter with age (R vs age: slopes=0.12 & -0.023 mm/yr; r=0.71 & -0.54; p=0.0002 & 0.0076, respectively), and Q less negative. Astigmatism was the predominant surface aberration (>90% of the surface variance), but did not vary significantly with age. Anterior and posterior surface tetrafoil RMS decreased significantly with age (slopes: -0.01 & -0.08 um/yr; r=-0.48 & -0.52; p=0.02 & 0.01, respectively). Anterior high order astigmatism increased significantly (p=0.04) and posterior trefoil, coma and 6th and higher RMS decreased significantly (p<0.05) with age. In general, there was a high correlation between anterior and posterior lens shapes, for R (r=-0.54, p=0.0076), Q (r=0.67, p=0.0004), astigmatism Z22 (r=0.47, p=0.02) and tetrafoil Z44 (r=0.85, p<0.0001), with slopes <0.51.
The human crystalline lens shows non-spherically symmetric surfaces. The increased steepness and negative asphericity in isolated young lenses is consistent with maximum accommodation. Astigmatism predominates, with anterior and posterior aligned axes. The change in tetrafoil with age may be associated to lens fibers branching. Although zonular tensions may cause topographic differences in the in vivo crystalline lens, this is the first comprehensive topographic study of the human lens.
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