It is a staging (grading) display for keratoconus. In the 1950s the Amsler-Krumeich staging system for
keratoconus was developed and is still frequently used today. However the Amsler-Krumeich only takes
anterior curvature and central corneal thickness into consideration. The ABCD Keratoconus Staging display
is a newly developed display, approved by the four major ophthalmology societies in the world. It looks at
A - anterior curvature, B - back (posterior) curvature, C - corneal thickness and D - distance corrected
visual acuity. Keratoconus is a progressive disease; this display detects progression easily aiding the
clinician to treat patients more successfully.