Table 4.

Pre- and Postoperative Comparison of Corneal Tomography

Parameter		Mechanical Epi-Off CXL	P Value	tPTK-Asst. Epi-off CXL	P Value	Wf-Guided tPRK CXL	P Value	P Valuea	P Valueb	P Valuec
K max, D	Preoperative	54.1 to 4.1	<0.001	53.6 to 5.3	0.619	52.6 to 3.1	<0.001
	Postoperative	55.4 to 4.4		53.7 to 5.0		49.1 to 2.6
	Mean difference	1.3 to 1.5		0.1 to 1.7		−3.5 to 2.4		0.012	<0.001	<0.001
	(95% CI)	(0.8 to 1.8)		(−0.4 to –0.7)		(−4.5 to −2.6)
CCT [µm]	Preoperative	482 to 33	<0.001	494 to 33	<0.001	491 to 31	<0.001
	Postoperative	469 to 34		478 to 33		470 to 27
	Mean difference	−13 to 11		−16 to 12		−21 to 14		0.513	<0.001	0.038
	(95% CI)	(−16 to −10)		(−20 to −13)		(−15 to −3)
TCT [µm]	Preoperative	472 to 33	<0.001	482 to 31	<0.001	481 to 28.9	<0.001
	Postoperative	460 to 32		461 to 33		442 to 28.0
	Mean difference	−12 to 11		−21 to 15		−39 to 18		0.035	<0.001	<0.001
	(95% CI)	(−15 to −9)		(−26 to −16)		(−46 to −31)
ISV	Preoperative	83.3 to 28.4	<0.001	79.4 to 35.1	0.620	73.1 to 20.2	<0.001
	Postoperative	90.2 to 28.0		78.5 to 33.1		56.3 to 20.6
	Mean difference	6.9 to 6.6		−0.90 to 11.2		−16.9 to 14.0		0.003	<0.001	<0.001
	(95% CI)	(4.9 to 8.9)		(−4.5 to 2.7)		(−22.3 to −11.4)
Anterior	Preoperative	6.6 to 2.6	0.548	8.8 to 4.0	0.084	4.9 to 2.6	<0.001
RMS-HOA	Postoperative	6.9 to 2.3		8.4 to 4.1		2.2 to 1.3
	Mean difference	0.3 to 1.2		−0.4 to 1.3		−2.7 to 1.7		0.796	<0.001	<0.001
	(95% CI)	(−0.7 to 1.3)		(−0.8 to 0.05)		(−3.4 to −2.0)

Data are expressed as mean ± standard deviation and mean differences additionally with 95% confidence intervals (95% CI).

CCT, central corneal thickness; HOA, high order aberrations; ISV, index of surface variance; K max, maximum keratometry; RMS, root mean square; TCT, thinnest corneal thickness.

Statistical significance (P < 0.05) is marked in bold face.

^aP-value between mechanical epi-off CXL and tPTK-asst. epi-off CXL.

^bP-value between mechanical epi-off CXL and Wf-guided tPRK CXL.

^cP-value between tPTK-asst. epi-off CXL and Wf-guided tPRK CXL.