Development of clinically based corneal nerves tortuosity indexes

Abstract

In-vivo specular microscopy provides information on the corneal health state. The correlation between corneal nerve tortuosity and pathology has been shown several times. However, because there is no unique formal definition of tortuosity, reproducibility is poor. Recently, two distinct forms of corneal nerve tortuosity have been identified, describing either short-range or long-range directional changes. Using 30 images and their manual grading provided by 7 experts, we automatically traced corneal nerves with a custom computerized procedure and identified the combination of geometrical measurements that best represents each tortuosity definition (Spearman Rank Correlation equal to 0.94 and 0.88, respectively). Then, we evaluated both of these tortuosity indexes in 100 images from 10 healthy and 10 diabetic subjects (5 images per subject). A Linear Discriminant Analysis showed a very good capability (accuracy 85%) to differentiate healthy subjects from pathological ones by using both tortuosity indexes together.