Table 3.

Mean difference (bias) for IOP measurements in pre-surgery with GAT and in post-surgery with GAT, CT1 and CT2.

	IOP difference	GATpost - GATpre	CT1 - GATpre	CT2 - GATpre
All	Mean difference (bias)	−3.569	0.324	0.912
	Wilcoxon test	Z = −8.618; p < 0.001	Z = −1.318; p = 0.187	Z = −3.523; p < 0.001
	Regression bias	b = −0.464; p < 0.001	b = −0.336; p < 0.001	b = −0.362; p < 0.001
LASIK	Mean difference (bias)	−3.9452	−0.192	0.425
	Wilcoxon test	Z = −7.383; p < 0.001	Z = −0.823; p = 0.410	Z = −1.687; p = 0.092
	Regression bias	b = −0.528; p < 0.001	b = −0.364; p < 0.001	b = −0.416; p < 0.001
PRK	Mean difference (bias)	−2.621	1.621	2.138
	Wilcoxon test	Z = −4.373; p < 0.001	Z = −3.16; p = 0.002	Z = −3.469; p = 0.001
	Regression bias	b = −0.346; p = 0.010	b = −0.327; p = 0.035	b = −0.283; p = 0.108

GAT, Goldmann applanation tonometer; CT1-CT2, convex tonometer; IOP intraocular pressure. Z, Wilcoxon test;b, regression coefficient; p, probability value.

Mean difference between measures with GATpre and all the devices in post-surgery were computed and tested for the absence of differences with the Wilcoxon test.

The results of regression bias (related to Bland-Altman) are also shown. Present significant differences are marked in cursive bold.