Keratometry using the Goldmann tonometer.

Keratometry using the Goldmann tonometer is a reliable and readily available guide to corneal astigmatism following cataract surgery. In regular corneal astigmatism the Goldmann tonometer rings are distorted into skewed ellipses. The axis of the cylinder can be measured by rotating the tonometer head until an undistorted ellipse is obtained. The power is then assessed by comparison with standard ellipses. The difference in the intracular pressure readings (mmHg) in the two principal meridians was also a good guide to the presence of astigmatism. Goldmann keratometry was performed by a single masked observer in 71 patients 8 weeks after routine extracapsular cataract surgery. This was compared with Javal-Schiotz Keratometry performed by an independent observer. In 83% of patients the axis was measured to within 20 degrees. The 95% confidence interval for the power was +/- 2.90 DC; and 87% of patients would have sutures removed appropriately.