中文说明：视网膜图像中含有血管，很难提取或分割出视盘。这段代码基本上是一种分割出血管的方法，用于精确分割视盘。这段代码是在matlab中实现的。
English Description：
retinal images contains blood vessels that make it difficult to extract or segment out the optic disk. this code is basically a way to segment out the blood vessels for accurate segmentation of optic disk. this code is implemented in matlab.