Table 2 Comparisons between ortho-k lens users and non-users.

From: The rate of orthokeratology lens use and associated factors in 33,280 children and adolescents with myopia: a cross-sectional study from Shanghai

 

Total (n = 33344)

Ortho-k lens users (n = 1021)

Ortho-k lens non-users (n = 32259)

p value

Mean ± SDa

Range

Mean ± SDa

Range

Mean ± SDa

Range

Boys, n (%)

16076 (48.3)

–

417 (40.8)

–

15659 (48.5)

–

<0.001b*

Age, years

13.02 ± 2.94

6~18

12.38 ± 2.57

6~18

13.04 ± 2.95

6~18

<0.001c*

Height, cm

158.00 ± 14.27

109.2~197.0

156.80 ± 12.83

119.5~192.8

158.03 ± 14.31

109.2~197.0

0.005c*

Weight, kgd

51.59 ± 15.46

16.5~116.3

48.44 ± 13.36

21.0~103.0

51.69 ± 15.51

16.5~116.3

<0.001c*

BMI, kg/m2d

20.20 ± 3.82

13.27~33.22

19.31 ± 3.24

13.31~32.95

20.22 ± 3.84

13.27~33.22

<0.001c*

Premature delivery, n (%)

1553 (4.7)

–

50 (5.0)

–

1503 (4.7)

-

0.697b

Age at initiation of refractive correction, years

10.90 ± 2.53

0~18

9.54 ± 2.32

1~17

10.96 ± 2.52

0~20

<0.001c*

Sleeping time on school days, hours

8.09 ± 1.07

4.85~12.08

8.12 ± 1.02

5.00~10.67

8.09 ± 1.16

4.85~12.08

0.320c

Parental myopia, n (%)

Neither

12240 (40.4)

–

155 (16.1)

–

12085 (41.2)

–

<0.001b*

Either

9533 (31.5)

–

278 (28.8

–

9255 (31.6)

–

 

Both

8515 (28.1)

–

531 (55.1)

–

7984 (27.2)

–

 

Academic stage, n (%)

Primary school

7195 (21.6)

–

285 (27.9)

–

6910 (21.4)

–

<0.001b*

Junior high school

13834 (41.6)

–

483 (47.3)

–

13351 (41.4)

–

 

Senior high school

12251 (36.8)

–

253 (24.8)

–

11998 (37.2)

–

 
  1. BMI body mass index.
  2. *P < 0.05 was considered statistically significant.
  3. aExcept where noted otherwise.
  4. bIndependent-samples t-test was used to identify statistical significance.
  5. cχ2 test was used to identify statistical significance.
  6. dWeight and BMI values less than the 1st percentile and greater than the 99th percentile were removed.
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