Pachymetry before or after applanation tonometry: does it matter?

We examined prospectively 60 healthy volunteers to evaluate if the accuracy of central corneal thickness (CCT) measurement is influenced by Goldmann applanation tonometry (GAT) and vice versa. The sequence of the examinations in the right eye was CCT--GAT--CCT, in the left eye GAT--CCT--GAT and the measurements were done consecutively. Two tonometry and five pachymetry measurements were averaged each time. Pearson correlation coefficients and Bland-Altman plots were used to assess the correlation between the measurements. In the right eye the mean CCT measurement before and after GAT was 565.22 +/- 32.99 micro and 566.04 +/- 33.50 micro (p = 0.34, r = 0.98) respectively. In the left eye the mean GAT before and after pachymetry was 19.38 +/- 4.71 mmHg and 19.16 +/- 4.32 mmHg (p = 0.43, r = 0.86) respectively. The study suggests that the sequence of the two examinations doesn't matter.