Table 2.

Comparison of parameters between eyes with and without myopic regression six months after myopic photorefractive keratectomy

Variables	Group 1 (n = 215 eye)	Group 2 (n = 39 eyes)	P -Value
Age (y), Mean ± SD	29.53 ± 7.29	33.38 ± 7.74	0.004
Pre-op Sphere (D), Mean ± SD	- 2.42 ± 1.70	- 2.92 ± 2.10	0.184
Pre-op Cylinder (D), Mean ± SD	- 1.01 ± 1.02	- 1.65 ± 1.24	0.001
Pre-op SEQ (D), Mean ± SD	- 2.72 ± 1.83	- 3.15 ± 2.10	0.208
Pre-op Mean K (D), Mean ± SD	43.84 ± 1.58	44.12 ± 1.82	0.443
Pre-op Mean K (≤ 43 D / 43 to 44.6 D / > 44.6 D), n (%)	76 (35.35) / 73 (33.95) / 66 (30.70)	11 (28.20) / 12 (30.77) / 16 (41.03)	0.431
Pre-op CCT (µm), Mean ± SD	526.56 ± 39.43	519.46 ± 39.45	0.265
Pre-op CCT (≤ 500 µm / > 500 µm), n (%)	64 (29.77) / 151 (70.23)	15 (38.46) / 24 (61.54)	0.281
RSB (μm), Mean ± SD	426.60 ± 44.76	408.90 ± 46.66	0.029
Ablation depth (μm), Mean ± SD	55.68 ± 21.81	67.79 ± 23.40	0.003
Size of optical zone (6 mm / 6.5 mm), n (%)	130 (60.47) / 85 (39.53)	25 (64.10) / 14 (35.90)	0.080

Abbreviations: n, number; y, year; SD, standard deviation; Pre-op, preoperative; Sphere, a spherical component of refractive error in manifest refraction; D, diopter; Cylinder, a cylindrical component of refractive error in manifest refraction; SEQ, a spherical equivalent of refractive error in manifest refraction; K, keratometry reading; %, percentage; CCT, central corneal thickness; μm, micrometer; RSB, residual stromal bed thickness; mm, millimeter. Not: P-values < 0.05 are shown in bold; Optical zone [18], the part of the corneal ablation area that receives the full intended refractive correction; Group 1, eyes without myopic regression six months after myopic photorefractive keratectomy; Group 2, eyes with myopic regression six months after myopic photorefractive keratectomy; Myopic regression, we designated myopic regression to be a - 0.25 D or more myopic shift documented at the six-month follow-up visit, and this was considered an unsuccessful outcome.