Abstract
Abstract The peripapillary retinal pigment epithelium-basement membrane (ppRPE/BM) layer angle was recently proposed as a potential index for estimating intracranial pressure noninvasively. However, the ppRPE/BM layer angle, measured from the optical coherence tomography (OCT) scans, varied across the radial directions of the optic disc. This made the ppRPE/BM layer angle difficult to be utilized in its full potential. In this study, we developed a mathematical model to quantify the ppRPE/BM layer angles across radial scans in relation to the ppRPE/BM 3D morphology in terms of its 3D angle and scanning tilt angles. Results showed that the variations of the ppRPE/BM layer angle across radial scans were well explained by its 3D angle and scanning tilt angles. The ppRPE/BM layer 3D angle was reversely fitted from the measured ppRPE/BM layer angles across radial directions with application to six eyes from four patients, who underwent medically necessary lumbar puncture. The fitted curve from our mathematical model matched well with the experimental measurements (R 2 > 0.9 in most cases). This further validated our mathematical model. The proposed model in this study has elucidated the variations of ppRPE/BM layer angle across 2D radial scans from the perspective of the ppRPE/BM layer 3D morphology. It is expected that the ppRPE/BM layer 3D angle developed in this study could be further exploited as a new biomarker for the optic disc.
Highlights
The peripapillary retinal pigment epitheliumbasement membrane layer angle was recently proposed as a potential index for estimating intracranial pressure noninvasively
It has been found out that the measured ppRPE/BM layer angle variation across the radial directions depends on the ppRPE/BM layer 3D angle and the scanning tilt angles, which could be calculated by reverse fitting the measured 2D data points in the radial optical coherence tomography (OCT) scans
If the axis of the OCT scanning beam aligned with the axis of the optic disc, e.g., no tilting, the measured ppRPE/BM layer angle will be the same across all radial directions (Figure 5b and c)
Summary
# Junfei Tong and Pengfei Dong contributed to this work. Optical coherence tomography (OCT) has been widely used in ophthalmology for providing high-resolution in vivo retinal structures [1,2]. We found that the angle of the peripapillary retinal pigment epithelium-basement membrane (ppRPE/BM) layer changed following the reduced intracranial pressure (ICP) procedure [6] This implies that the ppRPE/BM layer angle might be a potential index for the noninvasive assessment of the ICP, which is of great importance in clinical practice as abnormal ICP is a major risk factor for ophthalmological and neurological diseases [7,8,9,10]. Symmetric and untilted OCT scans at the nasal-temporal direction required the scanning beam of the OCT machine to be perpendicular to the optic disc, e.g., parallel to the axis of the optic nerve [13,14] In this way, the ppRPE/BM layer angle in each radial scan is approximately the same, indicating that the 3D shape of the ppRPE/BM layer is conical. The imaging data of six eyes from four patients, who underwent medically necessary lumbar puncture, were analyzed using the method
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