Skip to main content

Table 2 Changes in Parameters After Photorefractive Keratectomy and Comparisons Between the 6.0 mm Optical Zone and 6.5 mm Optical Zone Groups

From: Comparison of refractive outcomes after photorefractive keratectomy with different optical zones using Mel 90 excimer laser

Parametersa

3 months

(Mean ± SD)

6 months

(Mean ± SD)

Last visit

(Mean ± SD)

p value*

3–6 months

6–over 12 months

TCT (μm)

 6.0 OZ

452.81 ± 51.03

454.69 ± 52.18

460.06 ± 49.71

0.851

<  0.001

 6.5 OZ

474.04 ± 36.91

476.78 ± 35.67

480.75 ± 35.49

0.057

<  0.001

p value

0.035

0.030

0.035

  

ΔTCT/CD (μm/D)

 6.0 OZ

12.76 ± 5.13

12.38 ± 5.63

11.62 ± 5.98

0.061

0.001

 6.5 OZ

15.02 ± 3.89

14.61 ± 4.07

13.80 ± 4.12

0.058

<  0.001

p value

0.018

0.043

0.024

  

Sim K (D)

   

0.118**

 

6.0 OZ

38.73 ± 2.58

38.94 ± 2.31

39.24 ± 2.26

  

6.5 OZ

39.01 ± 2.29

39.00 ± 2.27

39.03 ± 2.17

  

p value

0.594

0.907

0.667

  

SE of MR (D)

 6.0 OZ

−0.61 ± 0.57

−0.52 ± 0.62

− 0.66 ± 0.50

0.968

0.072

 6.5 OZ

− 0.47 ± 0.45

−0.55 ± 0.57

−0.54 ± 0.42

0.474

0.660

p value

0.181

0.740

0.216

  

Sph (D)

 6.0 OZ

−0.33 ± 0.50

−0.20 ± 0.52

−0.33 ± 0.47

0.247

0.202

 6.5 OZ

−0.20 ± 0.50

−0.28 ± 0.63

−0.15 ± 0.63

0.309

0.443

p value

0.252

0.630

0.220

  

Cyl (D)

 6.0 OZ

−0.50 ± 0.29

−0.53 ± 0.27

−0.49 ± 0.25

0.475

0.156

 6.5 OZ

−0.55 ± 0.38

−0.47 ± 0.42

−0.58 ± 0.43

0.186

0.098

p value

0.788

0.173

0.191

  

RMS of HOAs (μm)

 6.0 OZ

0.72 ± 0.22

0.71 ± 0.22

0.68 ± 0.19

0.962

0.043

 6.5 OZ

0.53 ± 0.21

0.55 ± 0.23

0.56 ± 0.20

0.400

0.236

p value

<  0.001

0.001

0.005

  

SA (μm)

 6.0 OZ

0.58 ± 0.20

0.58 ± 0.21

0.57 ± 0.17

0.132

0.663

 6.5 OZ

0.34 ± 0.15

0.36 ± 0.14

0.37 ± 0.13

0.667

0.137

p value

<  0.001

<  0.001

< 0.001

  

Q value

 6.0 OZ

−0.55 ± 0.43

−0.56 ± 0.36

−0.54 ± 0.33

0.590

0.079

 6.5 OZ

−0.16 ± 0.32

−0.20 ± 0.32

−0.24 ± 0.33

0.496

0.148

p value

< 0.001

< 0.001

< 0.001

  

UDVA (logMAR)

 6.0 OZ

−0.17 ± 0.08

−0.17 ± 0.09

−0.16 ± 0.10

10.000

0.403

 6.5 OZ

−0.17 ± 0.10

−0.18 ± 0.09

−0.17 ± 0.09

0.637

0.763

p value

0.673

0.739

0.538

  
  1. SD Standard deviation, Sim K Simulated keratometry, TCT Thinnest corneal thickness, SE of MR Spherical equivalent of manifest refraction, RMS of HOAs Route mean square of higher order abberations, SA Spherical aberration, UDVA Uncorrected distance visual acuity, logMAR Logarithm of the minimum angle of resolution
  2. Significant difference at α < 0.05
  3. *Comparison of parameters between 6 months and beyond 12 months postoperatively. There was no significant difference in any parameter between three months and six months postoperatively
  4. **Sim K was normally distributed, thus the intergroup comparisons at three months, six months, and the last follow-up visit were made using the independent two samples t-test and comparisons in patterns of change by time between 6.0 OZ and 6.5 OZ were analyzed by two-way repeated measures ANOVA
  5. aNone of the parameters except Sim K were normally distributed, so intergroup comparisons were done using the Mann-Whitney U test, and the intragroup changes between 3 and 6 months and 6 months and the last visit were analyzed by the Wilcoxon signed ranks test