Assessing Corneal Endothelial Damage using Terahertz Spectroscopy and Support Vector Machines

The endothelial layer of the cornea plays a critical role in regulating its hydration by actively controlling fluid intake in the tissue via transporting the excess fluid out to the aqueous humor. A damaged corneal endothelial layer leads to perturbations in tissue hydration and edema, which can impact corneal transparency and visual acuity. We utilized a non-contact terahertz (THz) scanner designed for imaging spherical targets to discriminate between ex vivo corneal samples with intact and damaged endothelial layers. To create varying grades of corneal edema, the intraocular pressures of the whole porcine eye globe samples were increased to either 25, 35 or 45 mmHg for 4 hours before returning to normal pressure levels at 15 mmHg for the remaining 4 hours. Changes in tissue hydration were assessed by differences in spectral slopes between 0.4 to 0.8 THz. Our results indicate that the THz response of corneal samples is varied according to the differences in the endothelial cell density. We show that this spectroscopic difference is statistically significant and can be used to assess the intactness of the endothelial layer.