Abstract
Quantitative 3-D Optical Coherence Tomography was used to measure surface topography of 36 isolated human lenses, and to evaluate the relationship between anterior and posterior lens surface shape and their changes with age. All lens surfaces were fitted to 6th order Zernike polynomials. Astigmatism was the predominant surface aberration in anterior and posterior lens surfaces (accounting for ~55% and ~63% of the variance respectively), followed by spherical terms, coma, trefoil and tetrafoil. The amount of anterior and posterior surface astigmatism did not vary significantly with age. The relative angle between anterior and posterior surface astigmatism axes was on average 36.5 deg, tended to decrease with age, and was >45 deg in 36.1% lenses. The anterior surface RMS spherical term, RMS coma and 3rd order RMS decreased significantly with age. In general, there was a statistically significant correlation between the 3rd and 4th order terms of the anterior and posterior surfaces. Understanding the coordination of anterior and posterior lens surface geometries and their topographical changes with age sheds light into the role of the lens in the optical properties of the eye and the lens aging mechanism.
Highlights
The crystalline lens of the eye is a fascinating optical element, which, together with the cornea, transmits and refracts light to form an image of the world on the retina
We have studied the 3-D surface topography of 36 isolated human crystalline lenses, obtained using quantitative 3-D Optical Coherence Tomography (OCT)
The lens surface shape has been described with radii of curvature, asphericity, and Zernike polynomials up to the 6th order
Summary
The crystalline lens of the eye is a fascinating optical element, which, together with the cornea, transmits and refracts light to form an image of the world on the retina. The crystalline lens shows a gradient refractive index (GRIN) distribution, which changes with age [4,5,6,7,8]. The lens surface radii of curvature, and their changes with age and accommodation have been extensively measured both ex vivo, using, among other techniques, shadowphotography [11] and Optical Coherence Tomography (OCT) [12,13], and in vivo, using Purkinje imaging [14,15,16], Scheimpflug imaging [14,17], magnetic Resonance Imaging [18,19] and OCT [20]. The anterior and posterior lens surface radii of curvature tend to increase with age (at least up to past the presbyopia onset) [9,21], while in vivo, both surfaces tend to steepen with age [22]
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