Tracking Cataract by the Four-Line Method

An implementation of Scott's 'four-line' algorithm for estimating optic flow is presented. The application is the analysis of cataract motion in the human eye lens. Images are recorded using retro-illumination photography. Successive images recorded at up to a 6 month interval are used as the source for the flow recovery procedure. The four-line algorithm itself uses edge data from these images at several scales. A procedure for performing image registration and optic flow recovery using the same four-line algorithm is presented. Several examples of the algorithm output are given.