Corneal endothelial cell density (ECD)

Method

Corneal endothelial cell count per unit area by specular or confocal microscopy, sampled at the central cornea, with the counting method (automated, semi-automated, or manual fixed-frame) recorded on the edge.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

Benefit here means PRESERVATION, not growth - human corneal endothelium does not regenerate, so any measured fall is permanent and the direction is set to increase only so that the smaller loss scores as the better arm. Its near-miss is central corneal thickness, recorded at the same visit in the same corneal safety panel: both are described as corneal integrity numbers, but this is a cell count in cells/mm^2 and that is a distance in micrometres, and endothelial loss is irreversible while thickness fluctuates with oedema within days. Distinct also from coefficient of variation and hexagonality from the same specular image, which describe morphology rather than number.