Non-contact Specular Microscopy for Evaluation of Corneal Endothelium in Early Fuchs’ Endothelial Corneal Dystrophy

Abstract

 

Purpose

 

Early Fuchs’ Endothelial Corneal dystrophy (FECD) is characterized by guttata of varying density in the absence of clinically significant corneal edema. The purpose of the present study is to describe the use of non-contact specular microscopy to obtain accurate endothelial cell measurements despite variable guttata density.

 

Methods

 

Thirty-nine eyes of 24 patients with FECD and 49 eyes of 25 age-matched normal controls were imaged at the Doheny Eye Center. Three images of the central cornea were captured in each eye using the Konan NSP 9900 specular microscope (Irvine, CA). The calculations of endothelial cell density (ECD), coefficient of variation (CV), and percentage of hexagonal cells (HEX) were manually performed by certified anterior segment graders at the Doheny Image Reading Center using both Center and Flex Center methods. The surface area occupied by guttata in each image was measured by ImageJ.

 

Results

 

The ECD and HEX values obtained by the Center method were in concordance with those obtained by the Flex center method in normal eyes (P>0.05). In eyes with FECD, the mean ECD values were lower than that of the normal controls (P<0.05). In FECD eyes, ECD values obtained by the Center method were 2.4% higher than those using the Flex center method (P<0.001). However, when stratified by number of identifiable cells, ECD values derived by both methods were only significantly different when the number of analyzed cells was very low (NUM≤20). The CV values obtained by the Center method were 20.7% (P<0.001) lower than from the Flex center method. HEX values, however, were not different between methods (P=0.234), and also showed no difference in FECD eyes compared to normal corneas (P>0.05). Regardless of guttata surface area, the ECD, CV and HEX values from 3 different images obtained from the same eye were all similar. There was, however, a negative correlation between the guttata surface area and the ECD values when using both the Center (-0.340, P=0.001) and Flex Center methods (-0.433, P<0.001).

 

Conclusions

 

In early FECD, both Center and Flex center methods can be used to reliably determine ECD. ECD values are lower in FECD-affected corneas than in control eyes. The overall guttata area has a negative correlation with ECD value but is unrelated to CV and HEX.