Imaging of Birefringent Properties of Keratoconus Corneas by Polarization-Sensitive Optical Coherence Tomography

Abstract

The observed changes in the cornea's birefringence properties indicate a change in the arrangement of collagen fibrils in the corneal stroma associated with keratoconus. PS-OCT may be a useful tool for the study and diagnosis of corneal disease.

Conical scan pattern for enhanced visualization of the human cornea using polarization-sensitive OCT

“…This possibly indicates that multiple reflections at interfaces of lamellae or fibrils are the cause for depolarization. We want to point out that in vitro measurements of the cornea did not show depolarization from within the stroma [19,20,24]. This effect can only be observed when imaging is performed in vivo which has been outlined in a previous study using a time-domain PS-OCT instrument [36].…”

“…When imaging the human cornea with PS-OCT, distinct patterns in retardation and axis orientation can be observed, as shown by previous studies [19][20][21][22][23], that arise from the corneal shape and the corresponding fibril orientation. These patterns are distorted in case of diseases like keratoconus [24,25], making this technique a promising method for corneal diagnostics.…”

Fiber-based polarization-sensitive OCT for birefringence imaging of the anterior eye segment

“…4(c3) was caused by the calculation method of local birefringence shown in Eq. (19), where the multiplication of two pixels could enhance the speckle noise. By applying both processing methods, the best image quality of the local retardation was obtained as shown in Fig.…”

“…7(b3) had remaining speckle noise caused by the calculation method of local birefringence shown in Eq. (19). The coherent spatial Gaussian filter was effective to reduce it as shown in Fig.…”

“…Polarization-sensitive OCT (PS-OCT) has been developed to extend the function of OCT by exploiting the full nature of polarized light [14,15]. Previous studies of the anterior eye segment using PS-OCT showed promising potential in birefringence imaging for enhancing image contrast in normal tissue [16][17][18] and detecting abnormal birefringence in keratoconus corneas [19,20] and scar tissue [21,22]. In addition, it has been shown that scleral birefringence had statistically significant correlations with scleral elasticity and intraocular pressure in some in vivo and ex vivo studies [23][24][25], suggesting that scleral ultrastructure is partially related to the rheology of the eye.…”