Abstract
Purpose :
Patients with myopia and macular diseases show pathological changes in the scleral fibrous tissue and retinal pigment epithelium (RPE) layer. Conventional optical coherence tomography (OCT) is the gold standard for 3D ocular imaging but sometimes it fails to discriminate different tissues and retinal layer damage. This study demonstrates the significance of the polarization-sensitive OCT (PS-OCT) generated birefringence and depolarization contrasts to enhance the visibility of scleral structure and RPE layer abnormalities.
Methods :
A total of 40 Japanese subjects (20 macular defects and 20 myopic suspects) were measured using 1μm fundus PS-OCT and intensity, birefringence, and entropy images were reconstructed. Three regions of interest (ROI) of 60μm x15μm were manually selected based on contrast strength of birefringence and entropy. Low (ROI1), moderate (ROI2), and high (ROI3) contrast ROIs on the scleral birefringence image for myopic suspects and moderate (ROI1), low (ROI2), and high (ROI3) contrast ROIs are picked-up on the RPE entropy image that is an accurate depolarization metric. ROIs on their corresponding intensity images are also selected. Paired t-test analysis was performed between the ROIs of intensity, birefringence, and entropy images.
Results :
Intensity and birefringence images of myopic subjects as well as intensity and entropy images of macular defect subjects are shown in Fig. 1. The layered structures of sclera are observed in the birefringence image [Fig. 1(b)] while it appears as homogenous in the intensity image. The regional differences on the RPE layer from the entropy image are well discriminated [Fig. 1(d)]. The paired t-test results (Fig. 2) between the ROIs show that the birefringence and entropy can distinguish the regional differences (p < 0.001), while the OCT intensity shows a random variation region-wise (p > 0.05).
Conclusions :
PS-OCT-based birefringence reveals fibrous tissue-specific information of sclera and entropy provides a clear image of RPE layer damage like RPE loss or elevation. Thus PS-OCT can be a future clinical tool for evaluating spatial abnormalities of myopic and macular diseased eyes.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.