Inadvertent corneal indentation can cause artifactitious widening of the iridocorneal angle on ultrasound biomicroscopy

A 70-year-old Asian female with narrow angles underwent ultrasound biomicro scopy (UBM) darkroom provocative testing, The angle was narrow under light conditions and occluded in the dark, except for the inferior quadrant where the angle was wide and the iris concave. This was reproducible in four qua drants with the use of a small UBM eye cup but not the large one. A small e ye cup can indent the cornea, resulting in artifactitious angle widenening. Care must be taken when using the small eye cup not to press on the cornea .