The response of our new tonometer, as it is applied to the cornea, traces a typical curve shown in Figure 1. It rises sharply to a first maximum or crest, dips to a first minimum or trough, and then rises again to a central bump or maximum, all as a progressively greater force is applied to the probe to flatten a larger area of the cornea. As the probe is withdrawn, the curve continues essentially symmetrically. This is observed in both human and rabbit eyes. The curve can be interpreted in either or both of 2 ways. One explanation is that the first maximum or crest is an expression of the bending of the cornea at the limit of the applanated area. The height of the first minimum or trough then would give the intraocular pressure for the degree of applanation used. The depth of the trough would be a