Ramasubramanian Viswanathan, Glasser Adrian
*PhD College of Optometry, University of Houston, Houston, Texas (both authors).
Optom Vis Sci. 2015 Dec;92(12):1170-81. doi: 10.1097/OPX.0000000000000725.
Quantitative biometry measurements from uncorrected anterior segment optical coherence tomography (AS-OCT) images are inaccurate because of spatial and optical distortions. Prior reported distortion correction equations for the Visante AS-OCT were not reproducible. The goal was to calculate the distortions and provide equations to correct corneal parameters for the Visante AS-OCT to get a central corneal radius of curvature from young and older subjects.
Five contact lenses (CLs) of known front and back radii of curvature and central thickness were imaged using the Visante AS-OCT (Carl Zeiss, Dublin, CA). Contact lens surface coordinates from Visante images were identified and fitted with a circle using custom Matlab image analysis software. Spatial and optical distortions of the Visante image of the CL radii of curvature and thickness were calculated and corrected. Visante images were also captured from 24 younger (aged 21 to 36 years) and 30 older (aged 36 to 48 years) human subjects. Corneal radii of curvature and thickness measurements from these subjects were corrected, and intrasession and intersession repeatabilities of the corneal parameters were calculated.
Root mean square error of radius and power of the CL surfaces after distortion correction were 0.02 mm and 0.18D for the front and 0.011 mm and 0.11D for the back, respectively. Intraclass correlation coefficient for intrasession and intersession repeatability for all the corneal parameters from the human subjects was greater than 0.88 in both age groups.
A distortion correction algorithm was developed for the Visante AS-OCT and applied to extract human corneal radius of curvature measurements.
由于空间和光学畸变，未经校正的眼前节光学相干断层扫描（AS-OCT）图像的定量生物测量不准确。先前报道的Visante AS-OCT畸变校正方程不可重复。目标是计算畸变并提供方程以校正Visante AS-OCT的角膜参数，从而获得年轻和老年受试者的中央角膜曲率半径。
使用Visante AS-OCT（卡尔蔡司，加利福尼亚州都柏林）对五副已知前后曲率半径和中央厚度的隐形眼镜（CL）进行成像。从Visante图像中识别出隐形眼镜表面坐标，并使用定制的Matlab图像分析软件将其拟合为一个圆。计算并校正了Visante图像中隐形眼镜曲率半径和厚度的空间和光学畸变。还从24名年轻（21至36岁）和30名老年（36至48岁）人类受试者获取了Visante图像。校正了这些受试者的角膜曲率半径和厚度测量值，并计算了角膜参数的测量期间和测量间期重复性。
畸变校正后，隐形眼镜前表面半径和屈光度的均方根误差分别为0.02mm和0.18D，后表面为0.011mm和0.11D。两个年龄组中，人类受试者所有角膜参数的测量期间和测量间期重复性的组内相关系数均大于0.88。
为Visante AS-OCT开发了一种畸变校正算法，并应用于提取人类角膜曲率半径测量值。
