Peripheral-to-central ratio of Guttae: validity and reliability of an objective method to characterize severity of Fuchs endothelial corneal dystrophy

Purpose Common methods of measuring severity of Fuchs endothelial corneal dystrophy (FECD) are limited in objectivity, reliability, or start with a variable baseline that prevents distinguishing healthy from affected eyes. The aim of this study was to describe a method of grading FECD that overcomes these limitations. Methods Fifteen patients with Fuchs endothelial corneal dystrophy were included in the study. Guttae were imaged with a slit lamp beam 8 mm tall; the bottom 4 mm half of each image was divided into two equally-sized sections. Guttae were counted by four independent graders blinded to disease severity scores. The peripheral:central guttae ratio was compared to modified Krachmer clinical severity scores. The peripheral:central guttae ratio was compared between mild (severity 0.5-3) versus moderate-to-severe (severity 4-5) disease. Receiver operating characteristics defined optimal ratio cutoffs for mild versus moderate-to-severe disease. Results Increased peripheral guttae and peripheral:central guttae ratio correlated with Krachmer severity (p = 0.021 and p = 0.009, respectively). The difference between mild and moderate-to-severe cases for the peripheral:central guttae ratio was significant (p < 0.001). Inter-rater reliability of total guttae count was high (coefficient = 0.82, p < 0.001). A peripheral:central guttae ratio of 0.16 was the ideal cut-off point (area under the curve = 0.79, sensitivity = 0.78, and specificity = 0.80). Conclusion In this pilot study, the peripheral:central ratio of guttae correlates with subjective clinical severity of Fuchs dystrophy. It starts at a common baseline, has good inter-rater reliability, does not require dilation, and can be conducted with a smartphone and slit-lamp.

Automated summary

A new method for grading the severity of Fuchs endothelial corneal dystrophy (FECD) was described in this study, which overcomes limitations of current methods. By assessing the peripheral:central guttae ratio, the severity of the disease can be quickly and accurately evaluated.