Polarization-Sensitive Imaging of Choroid and Lamina Cribrosa With High-Penetration Polarization-Sensitive Optical Coherence Tomography

Abstract

 

Purpose:

 

To demonstrate the utility of newly developed high-penetration polarization sensitive optical coherence tomography (HP-PSOCT), especially to identify the chorio-scleral interface (CSI) and lamina cribrosa.

 

Methods:

 

6 eyes of 5 normal subjects were examined by a custom-built HP-PSOCT. This HP-PSOCT utilizes 1 um wavelength light as a probe and is based on swept-source OCT (SS-OCT) technology. The scanning speed was 30,000 depth scans/sec and the depth resolution was 11 um in tissue. A mirror image artifact, which was inevitable for SS-OCT, was eliminated by a reference phase modulation method, and wide depth measurement range and high sensitivity were achieved. A single OCT measurement provided a conventional OCT image (C-OCT) and a polarization sensitive phase retardation OCT (PS-OCT) image. Since they were created from a same OCT signal, they are inherently and perfectly registered to each other. A CSI and an anterior boundary of lamina cribrosa were identified by the PS-OCT images and compared to those shown in C-OCTs.

 

Results:

 

In PS-OCT images of all eyes, alteration of phase retardation at the deep posterior eye was observed. Since this alteration was an indicator of birefringent tissue, such as sclera, the region of sclera can be identified. Especially at the peripapillary region, strong alteration was observed, as shown in figure, because of deep penetration to sclera. The CSI determined by a PS-OCT image was well agreed with that determined by a C-OCT image, which has been believed to be CSI according to only empirical reasons. This agreement was found in 6 of 6 eyes. Although the anterior boundary of lamina cribrosa was not clear in C-OCT, the PS-OCT image showed clear contrast between prelaminar region and the lamina cribrosa.

 

Conclusions:

 

PSOCT supported the empirically determined location of CSI in C- OCT. PS-OCT would be useful to determine the CSI and the anterior boundary of lamina cribrosa.  

 

Keywords: choroid • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • lamina cribrosa