Abstract
Purpose :
During cataract surgery the lens is destroyed with ultrasound and its fragments become projectiles that may cause irreversible damage to the corneal endothelium. To increase the stability of the surgical environment and to coat the endothelium with a protection layer, Ophthalmic Viscosurgical Devices (OVDs) are injected into the anterior chamber. We present a method to quantitatively evaluate the still poorly understood protective properties and distribution of OVDs.
Methods :
For this work we imaged 100 porcine eyes. Each eye was imaged twice, resulting in 200 Optical Coherence Tomography (OCT) volume scans which stretched over 6x6x2.9mm3 (X x Y x Z) sampled at 512x128x1024 pixels. All images were acquired with a ZEISS LUMERA® 700 with ZEISS RESCAN® 700. Simulated cataract surgery was performed using a BSS-milk-solution (100:1) to create a high-contrast layer beneath the OVD (fig.1 A-C). Through the first part of the here presented pipeline we manually segmented the cornea (epithelium and endothelium) and the OVD BSS-solution boundary layer of approx. 3000 b-Scans. In the second part of the pipeline, a UNet based convolutional neural network (CNN) was trained to automatically segment the cornea (fig.1 (i)), BSS-milky emulsion (fig.1 (ii)) and background (fig.1 (iii)).
Results :
We measured for the first time the thickness of the OVD protection layer over a field of view of 6 by 6 mm. We accurately segmented a large data base of 200 OCT volumes and could quantitatively determine the protective properties of OVDs via thickness maps (fig.2 B). From these thickness maps we were able to derive the spatial distributions of every measurement (fig.2 B). We also found that there are notable differences between the layer thicknesses of the different kinds of OVDs.
Conclusions :
We presented a method to evaluate for the first time the thickness and homogeneity of protection layers formed by OVDs over a wide field of view, using OCT. This method will in a next step be utilized to investigate the minimal required OVD layer thickness to effectively protect the corneal endothelium.
This is a 2021 ARVO Annual Meeting abstract.