On repeated corneal applanation with the Goldmann and two non-contact tonometers

Abstract

Background: Several authors believe it is necessary to randomise the order in which contact and non-contact tonometers are used in comparison studies. This study was carried out to investigate the effect of repeated applanation on the measured intraocular pressure.

Methods: One set of measurements per session was made on each of three sessions (one session per day) with the Goldmann and two non-contact tonometers (Topcon CT80 and Keeler Pulsair EasyEye), in a pre-determined order, on one randomly selected eye of 120 subjects randomised to one of two groups. For session one, only the non-contact tonometers were used to assess the intraocular pressure of both groups. For session two, either non-contact or Goldmann tonometry was performed first and this order was reversed for session 3. Average intraocular pressures were compared between sessions to determine the presence or absence of effects on the intraocular pressure caused by prior repeated applanation with the Goldmann or either one (or both) of the non-contact tonometers.

Results: Prior applanation with a non-contact tonometer did not cause a significant (p > 0.05) reduction of the mean pressure measured with either non-contact tonometer. The mean pressure was slightly but significantly (p < 0.05) reduced (for both non-contact tonometers in both subject groups) when non-contact tonometry was performed after Goldmann tonometry. There was no significant difference (p > 0.05) between the pressures measured with the Goldmann tonometer prior to and subsequent to non-contact tonometry, in both subject groups.

Conclusion: A small but statistically significant reduction in the intraocular pressure was found following applanation with the Goldmann tonometer but not with either one of two non-contact tonometers.