Opt Lett. 2021 Mar 1;46(5):1085-1088. doi: 10.1364/OL.417903.
Off-axis detection methods in adaptive optics (AO) ophthalmoscopy can enhance image contrast of translucent retinal structures such as cone inner segments and retinal ganglion cells. Here, we propose a 2D optical model showing that the phase contrast produced by these methods depends on the offset orientation. While one axis provides an asymmetric light distribution, hence high phase contrast, the perpendicular axis provides a symmetric one, thus substantially lower contrast. We support this model with in vivo human data acquired with a multi-offset AO scanning light ophthalmoscope. Then, using this finding, we provide a post-processing method, named spatial-frequency-based image reconstruction, to optimally combine images from different off-axis detector orientations, significantly increasing the structural cellular contrast of in vivo human retinal neurons such as cone inner segment, putative rods, and retinal ganglion cells.
离轴探测方法在自适应光学（AO）眼底镜中可以增强诸如视锥内节和视网膜神经节细胞等半透明视网膜结构的图像对比度。在这里，我们提出了一个二维光学模型，表明这些方法产生的相位对比度取决于偏移方向。一个轴提供非对称的光分布，因此具有高的相位对比度，而垂直轴提供对称的光分布，因此对比度大大降低。我们使用多离轴 AO 扫描激光检眼镜获得的体内人眼数据来支持该模型。然后，利用这一发现，我们提供了一种后处理方法，称为基于空间频率的图像重建，以最优地组合来自不同离轴探测器方向的图像，显著提高了体内人视网膜神经元的结构细胞对比度，如视锥内节、假定的杆状细胞和视网膜神经节细胞。
