Cataract causes more than half of all blindness worldwide. The most effective treatment is surgery, where cataract is often replaced by intraocular lens (IOL). Beyond saving vision, toric IOL implantation is becoming increasingly popular to correct corneal astigmatism. It is important to precisely position and align the axis of IOL during surgery to achieve optimal post-operative astigmatism correction. Comparing with conventional manual marking, automated markerless IOL alignment can be faster, more accurate and non-invasive. Here we propose a framework for computer-assisted intraoperative IOL positioning and alignment based on detection and tracking. Firstly, the iris boundary was segmented and the eye center was determined. A statistical sampling method was developed to segment iris and generate training labels, and both conventional algorithms and deep convolutional neural network (CNN) methods were evaluated. Then, regions of interests (ROIs) containing high density of scleral capillaries were used for tracking eye rotations. Both correlation filter and CNN methods were evaluated for tracking. Cumulative errors during long-term tracking were corrected using a reference image. Validation studies against manual labeling using 7 clinical cataract surgical videos demonstrated that the proposed algorithm achieved an average position error around 0.2 mm, an axis alignment error of < 1 ∘^{\circ}, and a frame rate of > 25 FPS, and can be potentially used intraoperatively for markerless IOL positioning and alignment during cataract surgery.

中文翻译：

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白内障手术期间计算机辅助术中环面人工晶状体定位和对准


白内障导致全世界一半以上的失明。最有效的治疗方法是手术，通常用人工晶状体（IOL）代替白内障。除了挽救视力之外，环面人工晶状体植入术在矫正角膜散光方面也越来越受欢迎。在手术过程中精确定位和对准 IOL 轴对于实现最佳的术后散光矫正非常重要。与传统的手动标记相比，自动无标记人工晶状体对准可以更快、更准确且非侵入性。在这里，我们提出了一个基于检测和跟踪的计算机辅助术中 IOL 定位和对齐框架。首先，分割虹膜边界并确定眼睛中心。开发了一种统计采样方法来分割虹膜并生成训练标签，并对传统算法和深度卷积神经网络（CNN）方法进行了评估。然后，包含高密度巩膜毛细血管的感兴趣区域（ROI）用于跟踪眼球旋转。相关滤波器和 CNN 方法都进行了跟踪评估。使用参考图像校正长期跟踪期间的累积误差。使用 7 个临床白内障手术视频对手动标记进行的验证研究表明，所提出的算法实现了约 0.2 mm 的平均位置误差、< 1 ∘^{\circ} 的轴对齐误差和 > 25 FPS 的帧速率，并可在白内障手术期间用于术中无标记 IOL 定位和对准。