TABLE 2.

Basic biometric parameters of the four surgery groups.

Parameters	tPRK	tPRK Xtra	FS-LASIK	FS-LASIK Xtra	F	P
Age(years)	25.1 ± 4.1	23.1 ± 5.4	25.3 ± 4.3	24.3 ± 6.4	1.348	0.261
gender ratio	11/26	15/20	18/17	10/26	5.711	0.127
CCT(μm)	542.8 ± 32.0	535.9 ± 33.1	549.3 ± 28.0	546.7 ± 27.4	1.302	0.276
OZD(mm)	6.36 ± 0.39	6.16 ± 0.48	6.39 ± 0.29	6.28 ± 0.45	2.265	0.084
SE(D)	-5.31 ± 1.96	-5.44 ± 2.02	-5.46 ± 1.70	-5.13 ± 1.66	0.231	0.874
ASD(μm)	85.6 ± 22.0	84.2 ± 19.5	82.1 ± 23.1	77.8 ± 18.5	0.957	0.415
bIOP(mmHg)	15.0 ± 1.8	15.4 ± 2.0	14.7 ± 1.8	15.6 ± 2.2	1.462	0.228
Risk classification	-	1.51 ± 0.70	-	1.36 ± 0.59	2.456	0.123

Gender ratio was calculated as Male/Female, CCT, means central corneal thickness; OZD, means optical zone diameter; SE, means spherical equivalent of manifest refractive error correction; ASD, means Ablated stromal depth (ASD), bIOP, means biomechanically corrected intraocular pressure provided by Corvis ST.