Corneal displacement during tonometry with a noncontact tonometer.

Purpose: To measure the extent of corneal displacement during the early phase of tonometry using a noncontact tonometer and to determine the factors that affect the extent of the displacement.

Methods: The cornea was photographed in profile by use of a high-speed camera during tonometry with a noncontact tonometer. The frame rate of the camera was 5,000 frames/s. The extent of the displacement of the central corneal area at 13.2 ms after application of the air puff was measured in 115 healthy volunteers. The factors that affected the extent of the corneal displacement were determined by stepwise multiple linear regression analysis.

Results: The subjects' age, sex, intraocular pressure (IOP), central corneal thickness, anterior chamber depth, and axial length were selected by the stepwise method. The results of the multiple linear regression analysis showed that subjects with low IOP, of older age, and of male sex had significantly greater displacement of the central cornea.

Conclusions: High-speed photography can be used to evaluate the degree of corneal displacement during tonometry with a noncontact tonometer. The amount of corneal displacement is affected by the individual's IOP, age, and sex.