Rylander H Grady, Kemp Nate J, Park Jesung, Zaatari Haitham N, Milner Thomas E
The Biomedical Engineering Laser Laboratories, Department of Biomedical Engineering, The University of Texas at Austin, 1 University Station #C0800, Austin, TX 78712, USA.
Exp Eye Res. 2005 Jul;81(1):81-9. doi: 10.1016/j.exer.2005.01.009.
The purpose of this study was to measure the peripapillary retinal nerve fiber layer (RNFL) thickness, phase retardation (PR), and depth-resolved birefringence (Deltan) of the normal primate eye using Enhanced Polarization-Sensitivity Optical Coherence Tomography (EPS-OCT). Both eyes of two rhesus monkeys were imaged with EPS-OCT. A multiple incident polarization state nonlinear fitting algorithm was used to determine RNFL phase retardation. RNFL thickness (RNFLT) was determined from the corresponding EPS-OCT intensity image and phase retardation per unit depth (PR/UD, proportional to Deltan) was calculated by dividing PR by RNFLT. Peripapillary area maps consisting of pixels uniformly distributed along a radius from 0.8 to 1.8 mm from the center of the optic nervehead were constructed for RNFLT, PR, and PR/UD. Average PR/UD in the superior and inferior quadrants was 18 degrees /100 mivrom (Deltan=4.2 x 10(-4)) and average PR/UD in the nasal and temporal quadrants was 6.3 degrees /100 microm (Deltan=1.5 x 10(-4)). Relative magnitude of PR radial gradient is similar to that of RNFLT radial gradient and no radial gradient was observed for PR/UD. Polarization-dependent amplitude attenuation per unit depth (PDAA/UD) was 0.02 rad/100 microm in thick RNFL regions. RNFL birefringence was higher in the arcuate bundles compared to nasal and temporal fibers (P=0.001). Birefringence was nearly equal in nasal and temporal quadrants. No statistically significant (P=0.01) radial gradient of birefringence was observed in any quadrant. RNFL birefringence is believed to originate from anisotropic structures within the cytoskeleton of the parallel axons. Birefringence differences presented in this study cannot be explained by the known axon diameter distribution around the optic nervehead and suggest other sources of the birefringence signal including neurotubules and neurofilaments.
本研究的目的是使用增强偏振敏感光学相干断层扫描（EPS - OCT）测量正常灵长类动物眼睛的视乳头周围视网膜神经纤维层（RNFL）厚度、相位延迟（PR）和深度分辨双折射（Deltan）。对两只恒河猴的双眼进行了EPS - OCT成像。使用多入射偏振态非线性拟合算法确定RNFL相位延迟。从相应的EPS - OCT强度图像确定RNFL厚度（RNFLT），并通过将PR除以RNFLT来计算每单位深度的相位延迟（PR/UD，与Deltan成比例）。构建了由沿距视神经乳头中心0.8至1.8 mm半径均匀分布的像素组成的视乳头周围区域图，用于RNFLT、PR和PR/UD。上象限和下象限的平均PR/UD为18度/100微米（Deltan = 4.2×10⁻⁴），鼻象限和颞象限的平均PR/UD为6.3度/100微米（Deltan = 1.5×10⁻⁴）。PR径向梯度的相对大小与RNFLT径向梯度相似，且未观察到PR/UD的径向梯度。在厚RNFL区域，每单位深度的偏振相关幅度衰减（PDAA/UD）为0.02弧度/100微米。与鼻侧和颞侧纤维相比，弓形束中的RNFL双折射更高（P = 0.001）。鼻象限和颞象限的双折射几乎相等。在任何象限中均未观察到具有统计学意义（P = 0.01）的双折射径向梯度。RNFL双折射被认为源自平行轴突细胞骨架内的各向异性结构。本研究中呈现的双折射差异无法用视神经乳头周围已知的轴突直径分布来解释，提示双折射信号的其他来源包括神经微管和神经丝。
