Self-tonometry with the Ocuton S: evaluation of accuracy in glaucoma patients

To compare two methods of measuring intraocular pressure (IOP) and to evaluate whether repeated measurements taken with the Ocuton S applanation self-tonometer can improve reliability.

Ocuton S and Goldmann applanation tonometry (GAT), and corneal thickness measurements taken with the Orbscan topography system, were successfully performed in 64 of 68 glaucoma patients.

The median IOPs were 15.5 mmHg using GAT, and 16 mmHg using the first self-taken Ocuton S measurement (n = 64). The differences between the median of the GAT measurements and the first Ocuton S measurement, and the medians of the three and six separate Ocuton S measurements were within 3 mmHg in 52%, 59% and 67% of cases, respectively. The mean corneal thickness of all evaluated eyes was 545.3 microm. There was no effect of corneal thickness on the accuracy of either of the two devices (p > 0.05).

Repeated measurements can improve the reliability of the Ocuton S. However, even with repeated measurements only every second patient succeeds in obtaining reliable measurements.