Abstract
Purpose :
Cataracts increase the amount of intraocular light scattering in the crystalline lens causing vision impairment by blurring and reducing the contrast in retinal images. Wavefront shaping techniques in combination with the Optical Memory Effect (OME) have been suggested for the optical (non-surgical) correction of scattering in cataractous lenses. In this context, we aim to characterize the scattering properties of excised human lenses by measuring their OME.
Methods :
The Optical Memory Effect is an intrinsic correlation of scattering media that provides the isoplanatic patch of a cataract’s correction imaging technique, determining how the transmitted speckle pattern changes with a tilt/shift of the incident beam. We measured it using a 594nm laser incident on cataractous lenses by recording the transmitted pattern. With the lens mounted on a shift/tilt holder, the similarity between the speckle patterns for different values of shift and tilt of the lens was examined via cross-correlation. We characterized the OME for different cataract stages. For each case, we also included other scattering metrics, as the straylight parameter, measured with the Optical Integration Method, the transport mean free path and contrast image quality, studying the variation of the OME with the measured scattering parameters. We measured a total of 22 lenses of donors aged between 29 and 67, leaving the cataract develop with time to increase the scattering range.
Results :
We found that OME is non-negligible for cataracts, being strongly dependent on the scattering strength. For severe cataracts (straylight parameter Log10[s]=2.45 and image contrast below 16%), the OME was mainly limited by a tilt of 6 deg, whereas for weak cataracts (Log10[s]=1.32 and image contrast 90%) this range was extended up to 10 deg. We also found a linear relationship between the straylight parameter, image contrast and OME decorrelation, providing us with a new tool for the prediction of the OME range when only quantitative scattering measurements are taken.
Conclusions :
The OME of cataractous excised human lenses has been measured for the first time. Together with quantitative scattering parameters measured simultaneously, it provides with a useful tool for the optical correction of cataracts using wavefront shaping techniques. This work paves the way to new potential approaches for the non-invasive and real-time correction of cataracts with wearable devices.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.