Abstract
The full shape of the accommodating crystalline lens was estimated using custom three-dimensional (3-D) spectral OCT and image processing algorithms. Automatic segmentation and distortion correction were used to construct 3-D models of the lens region visible through the pupil. The lens peripheral region was estimated with a trained and validated parametric model. Nineteen young eyes were measured at 0-6 D accommodative demands in 1.5 D steps. Lens volume, surface area, diameter, and equatorial plane position were automatically quantified. Lens diameter & surface area correlated negatively and equatorial plane position positively with accommodation response. Lens volume remained constant and surface area decreased with accommodation, indicating that the lens material is incompressible and the capsular bag elastic.
Highlights
Understanding the changes in lens geometry with accommodation is critical to fully understand the lenticular mechanism of accommodation and for the design and evaluation of solutions for presbyopia.Morphological changes in the lens with accommodation have been obtained in vivo using various optical imaging techniques including Purkinje [1, 2], Scheimpflug [2,3,4], and Optical Coherence Tomography (OCT) [5,6]
We have shown that the proposed method shows improved performance in comparison with state-of-the-art methods, leading to volume, diameter and equatorial plane position (EPP) estimation errors approximately 3, 6, and 4 times lower on average, respectively
Images were acquired with a custom spectral Optical Coherence Tomography system based on a fiber-optics Michelson interferometer configuration with a superluminiscent diode (λ0 = 840 nm, ∆λ = 50 nm) as a light source, and a spectrometer as a detector [27]
Summary
Morphological changes in the lens with accommodation have been obtained in vivo using various optical imaging techniques including Purkinje [1, 2], Scheimpflug [2,3,4], and Optical Coherence Tomography (OCT) [5,6]. In a recent study we reported changes in lens surface elevation maps and biometry based on quantitative three-dimensional (3-D) spectral OCT [6]. While the reported changes of the lens during accommodation resulting from the ciliary muscle forces are consistent with the Helmholtz’s theory of accommodation: steepening of the lens surfaces, increase in lens thickness (LT) and decrease in anterior chamber depth (ACD), estimates of other parameters not possibly measured directly with optical imaging techniques would allow a more complete experimental assessment of the theory. Critical parameters include the lens volume (VOL), the lens surface area (LSA), and the diameter of the lens at the equatorial plane (DIA)
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