Optical memory effect of excised cataractous human crystalline lenses

Abstract

Cataracts increase the amount of scattered light in the crystalline lens producing low-contrast retinal images and causing vision impairment. The Optical Memory Effect is a wave correlation of coherent fields, which can enable imaging through scattering media. In this work, we characterize the scattering properties of excised human crystalline lenses by measuring their optical memory effect and other objective scattering parameters, finding the relationship between them. This work has the potential to help fundus imaging techniques through cataracts as well as the non-invasive correction of vision through cataracts.

Fig. 1.

Schematic of the setup for the measurement of the PSF of the crystalline lenses.

Fig. 2.

(a) Setup for the dark field photography. Only the scattered light is captured by the camera. (b) Dark Field Image of a crystalline lens with a mature cataract. (c) USAF-target image through lens shown in (b) with a Michelson Contrast of 0.64.

Fig. 3.

Schematic of the Optical Integration Method system, for the measurement of the straylight as function of θ in the different lenses. Green ray tracing depicts the light trajectory when the lens is tested. The focusing for each lens is manually adjusted by the axial displacement of the camera.

Fig. 4.

Schematic of the experimental configuration for the measurement of the shift and tilt optical memory effect. A laser beam at 594 nm wavelength impinges onto a crystalline lens mounted in a translation and rotation stage, after which a CCD camera is placed to record the transmitted speckle patterns.

Fig. 5.

(a)-(c) Dark Field Images of crystalline lenses with straylight parameters at 3 degrees of 1,76, 1,99 and 2,47, respectively. (d)-(f) Images of an USAF test target through the tested lenses shown in panels (a)-(c), respectively. (g)-(i) PSF of the corresponding lenses in the same columns. The image corresponds to an area of 1mm².

Fig. 6.

(a) Normalized cross-correlation of the transmitted speckle patterns for different values of lateral translation, in steps of 20 micrometers. The different curves represent three different crystalline lenses of different opacities, with Straylight parameters (Log₁₀(s)) at 3 degrees of 1,76, 1,92 and 2,47, from quasi transparent to opaque. (b) Normalized cross-correlation of the transmitted speckle patterns for different values of tilt or rotation, in steps of 10 arcmin, for the different lenses. (c) Graph showing the relationship between the Michelson contrast of the images and the straylight parameter at 3 degrees. (d) Representation of the normalized cross-correlation for a tilt of 1 degree vs the straylight parameter at 3 degrees of the different lenses. (e) Graph representing the normalized cross-correlation for a shift of 400 um vs the straylight parameter at 3 degrees of the different lenses. (f) In this graph we represent the angles at which the transmitted speckle patterns are decorrelated by half as a function of the straylight of the cataractous lenses, which provides the isoplanatic patch of the media. All the dashed lines represent the standard deviation of the data.