In vivo human crystalline lens topography

Abstract

Custom high-resolution high-speed anterior segment spectral domain optical coherence tomography (OCT) was used to characterize three-dimensionally (3-D) the human crystalline lens in vivo. The system was provided with custom algorithms for denoising and segmentation of the images, as well as for fan (scanning) and optical (refraction) distortion correction, to provide fully quantitative images of the anterior and posterior crystalline lens surfaces. The method was tested on an artificial eye with known surfaces geometry and on a human lens in vitro, and demonstrated on three human lenses in vivo. Not correcting for distortion overestimated the anterior lens radius by 25% and the posterior lens radius by more than 65%. In vivo lens surfaces were fitted by biconicoids and Zernike polynomials after distortion correction. The anterior lens radii of curvature ranged from 10.27 to 14.14 mm, and the posterior lens radii of curvature ranged from 6.12 to 7.54 mm. Surface asphericities ranged from −0.04 to −1.96. The lens surfaces were well fitted by quadrics (with variation smaller than 2%, for 5-mm pupils), with low amounts of high order terms. Surface lens astigmatism was significant, with the anterior lens typically showing horizontal astigmatism (Z22 ranging from −11 to −1 µm) and the posterior lens showing vertical astigmatism (Z22 ranging from 6 to 10 µm).

Three-dimensional OCT based guinea pig eye model: relating morphology and optics

“…We found that the greatest proportion of the eye's power (65%) was due to the cornea, although the crystalline lens played a significant role in the eye's high order aberrations. As found in humans using OCT-based crystalline lens topography both ex vivo [31] and in vivo [12,17], we found that the astigmatism of the anterior and posterior lens tends to be crossed, and higher amounts of surface irregularities in the posterior lens.…”

“…In previous works we have reported 3-D anterior segment biometry in human eyes in vivo, including anterior and posterior corneal and lenticular surface elevation maps [12][13][14][15][16][17], interocular distances along well identified axes [18] and full crystalline lens, beyond the margins of the pupil [19]. Quantitative analysis is possible by correction of distortions (fan, arising from the scanning architecture; optical, due to the refraction in the optical surfaces) and new automatic image processing algorithms that have allowed quantification.…”

OCT 3-D surface topography of isolated human crystalline lenses

“…For example, it is well known that corneal astigmatism changes from with-the-rule to against-the-rule astigmatism with aging [48][49][50]. Previous studies suggested that the astigmatism axis of the anterior lens surface is vertical [51][52][53]. We did not find a significant correlation between anterior or posterior astigmatism axis and age.…”

“…This information could be used in a ray tracing analysis that incorporates data from cornea and lens GRIN distribution [21,52,54,55].…”

OCT-based crystalline lens topography in accommodating eyes

“…The SD-OCT instrument, and a set of algorithms for image processing and distortion correction (fan and optical) to obtain anterior and posterior corneal and crystalline lens topographies from OCT images have been described in detail in previous publications [26][27][28][29][30][31][32]. Briefly, the set-up is based on a fiber-optics Michelson interferometer configuration with a superluminiscent diode (λ 0 = 840 nm, ∆λ = 50 nm) as a light source, and a spectrometer consisting of a volume diffraction grating and a CMOS camera as a detector.…”