Birefringent imaging of limbal region using Jones matrix optical coherence tomography

Abstract

Purpose : This study aims at depth-wise visualization (intensity and birefringence) of the limbal region using Jones matrix optical coherence tomography (JM-OCT).

Methods : A normal subject (F, 31 y/o) was imaged using a custom built JM-OCT. The system uses a probe wavelength of 1.31 µm and specifically designed for anterior eye. 32 scans across the eye circumference was obtained. Each scan covers 6 × 6 mm transversal area (512 A-lines × 128 frames). A single scan provides a set of four OCT images which form a Jones matrix tomography (JMT) of the sample. OCT intensity is obtained by summation of two OCT images from JMT (non-delayed channels). Birefringence tomography was obtained by processing the JMT by a birefringence estimator based on maximum a-posteriori theory. The OCT volume is flattened to the tissue surface, and then the scleral-uveal interface plane is identified. The en-face slices at 0, 24, 48, 72 and 96 microns above the scleral-uveal interface were obtained for both the OCT intensity and birefringence flattened tomographic volumes. The en-face sum projection of inverted intensity obtained for all volumes are co-registered and patched together by ImageJ with MosaicJ plugin. The same registration information was used to create wide field intensity and birefringence maps at each depth.

Results : Fig 1(a) shows the morphology along with (b) intensity and (c) birefringence cross-sections at the superior eye. High birefringence (green) is seen on both sides of the lumen of Schlemm’s canal (red arrow). It could be scleral spur (+) anterior to the location of ciliary muscle and terminating scleral tissue (*) posterior to corneal boundary. Fig 2 shows the wide field mosaics of intensity and birefringence at 0, 24, 48, 72 and 96-µm above the sclera-uveal interface. The lumen of Schlemm’s canal is evidently seen as low scattering band in the intensity map (Fig 2(a)). The corresponding birefringence map reveals high birefringence zone posterior to the lumen along the sclera-uveal interface (+). Two high birefringence bands interspersed with a low birefringence band is noticed at slices above the scleral-uveal boundary. The birefringence maps provides improved contrast than the intensity maps to highlight the complex morphology of the limbal area.

Conclusions : Morphological and functional differences in the structural organization of limbal region could be visualized using multiple contrast information using JM-OCT.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.