Background
Methods
Statistical analysis
Results
Prevalence of astigmatism
Participant characteristics | |
---|---|
Age (years) | n (%) |
5 | 1 (0.02%) |
6 | 292 (6.1%) |
7 | 345 (7.2%) |
8 | 359 (7.5%) |
9 | 369 (7.7%) |
10 | 360 (7.5%) |
11 | 385 (8.0%) |
12 | 353 (7.3%) |
13 | 374 (7.8%) |
14 | 365 (7.6%) |
15 | 371 (7.7%) |
16 | 361 (7.5%) |
17 | 370 (7.7%) |
18 | 370 (7.7%) |
19 | 121 (2.5%) |
20 | 5 (0.1%) |
Mean (SD) | 12.3 (3.8) |
Gender | |
Male | 2647 (55.1%) |
Female | 2154 (44.9%) |
Grade | |
Kindergarten | 381 (7.9%) |
Grade 1 | 331 (6.9%) |
Grade 2 | 366 (7.6%) |
Grade 3 | 371 (7.7%) |
Grade 4 | 367 (7.6%) |
Grade 5 | 376 (7.8%) |
Grade 6 | 368 (7.7%) |
Grade 7 | 376 (7.8%) |
Grade 8 | 360 (7.5%) |
Grade 9 | 346 (7.2%) |
Grade 10 | 383 (8.0%) |
Grade 11 | 373 (7.8%) |
Grade 12 | 403 (8.4%) |
School location | |
Urban | 2691 (56.1%) |
Rural | 2110 (43.9%) |
Spherical equivalent of more astigmatic eye (Diopters) | |
≤ −6 | 351 (7.3%) |
> −6, ≤ −5 | 267 (5.6%) |
> −5, ≤ −4 | 414 (8.6%) |
> −4, ≤ −3 | 510 (10.6%) |
> −3, ≤ −2 | 584 (12.2%) |
> −2, ≤ −1 | 768 (16.0%) |
> −1, ≤ −0.5 | 557 (11.6%) |
> −0.5, < 0.5 | 1076 (22.4%) |
≥ 0.5, < 1.0 | 171 (3.6%) |
≥ 1.0 | 103 (2.2%) |
Cylinder of more astigmatic eye (diopters) | |
0 | 204 (4.3%) |
> 0, < 0.5 | 952 (19.8%) |
≥ 0.5, < 1.0 | 2063 (43.0%) |
≥ 1.0, < 1.5 | 902 (18.8%) |
≥ 1.5, < 2.0 | 349 (7.3%) |
≥ 2.0, < 2.5 | 162 (3.4%) |
≥ 2.5, < 3.0 | 66 (1.4%) |
≥ 3.0, < 4.0 | 73 (1.5%) |
≥ 4.0 | 30 (0.6%) |
Mean (SD) | 0.87 (0.75) |
Median (1st quartile, 3rd quartile) | 0.75 (0.50, 1.12) |
Minimum, Maximum | 0, 15 |
Astigmatism ≥ 1.5 diopters | 680 (14.2%) |
With-the-rule | 575 (84.6%) |
Against-the-rule | 11 (1.62%) |
Oblique | 94 (13.8%) |
Astigmatism ≥ 3.0 diopters | 103 (2.15%) |
With-the-rule | 93 (90.3%) |
Against-the-rule | 2 (1.94%) |
Oblique | 8 (7.77%) |
Characteristics | N | Cylinder power in diopters: Mean (SD) | Astigmatism ≥1.5 D (%) | Astigmatism ≥3.0 D (%) | Degree of astigmatism (D) among students with astigmatism (N = 680) Mean (SD) |
---|---|---|---|---|---|
Age (years) | P < 0.0001 | P < 0.0001 | P = 0.02 | P = 0.81 | |
≤ 6 | 293 | 0.69 (0.61) | 25 (8.5%) | 3 (1.0%) | 2.17 (0.97) |
7 | 345 | 0.64 (0.57) | 25 (7.3%) | 6 (1.7%) | 2.19 (0.79) |
8 | 359 | 0.73 (0.76) | 27 (7.5%) | 5 (1.4%) | 2.24 (0.94) |
9 | 369 | 0.73 (0.58) | 30 (8.1%) | 5 (1.4%) | 2.17 (0.72) |
10 | 360 | 0.71 (0.59) | 24 (6.8%) | 6 (1.7%) | 2.26 (1.07) |
11 | 385 | 0.78 (0.85) | 40 (10.4%) | 5 (1.3%) | 2.08 (0.65) |
12 | 353 | 0.96 (0.93) | 54 (15.3%) | 12 (3.4%) | 2.37 (0.94) |
13 | 374 | 0.89 (0.62) | 56 (15.0%) | 7 (1.9%) | 2.04 (0.62) |
14 | 365 | 0.90 (0.63) | 56 (15.3%) | 4 (1.1%) | 2.05 (0.64) |
15 | 371 | 1.02 (0.78) | 67 (18.1%) | 14 (3.8%) | 2.36 (0.82) |
16 | 361 | 1.09 (1.03) | 93 (25.8%) | 5 (1.4%) | 2.17 (1.48) |
17 | 370 | 1.07 (0.86) | 76 (20.5%) | 11 (3.0%) | 2.27 (0.88) |
18 | 370 | 1.07 (0.87) | 85 (23.0%) | 15 (4.1%) | 2.26 (1.04) |
≥ 19 | 126 | 1.06 (0.79) | 22 (17.5%) | 5 (4.0%) | 2.36 (0.95) |
Gender | P < 0.0001 | P < 0.0001 | P = 0.001 | P = 0.04 | |
Male | 2647 | 0.92 (0.89) | 427 (16.1%) | 73 (2.8%) | 2.27 (1.06) |
Female | 2154 | 0.82 (0.80) | 253 (11.8%) | 30 (1.4%) | 2.13 (0.78) |
Grade | P < 0.0001 | P < 0.0001 | P = 0.02 | P = 0.88 | |
Kindergarten | 381 | 0.67 (0.58) | 29 (7.6%) | 3 (0.8%) | 2.16 (0.91) |
Grade 1 | 331 | 0.66 (0.65) | 27 (8.2%) | 8 (2.4%) | 2.33 (0.95) |
Grade 2 | 366 | 0.74 (0.71) | 26 (7.1%) | 5 (1.4%) | 2.14 (0.79) |
Grade 3 | 371 | 0.73 (0.57) | 30 (8.1%) | 4 (1.1%) | 2.16 (0.69) |
Grade 4 | 367 | 0.72 (0.62) | 28 (7.6%) | 7 (1.9%) | 2.27 (1.11) |
Grade 5 | 376 | 0.82 (0.84) | 41 (10.9%) | 4 (1.1%) | 2.03 (0.56) |
Grade 6 | 368 | 0.93 (0.92) | 56 (15.0%) | 12 (3.3%) | 2.35 (0.96) |
Grade 7 | 376 | 0.91 90.61) | 57 (15.2%) | 6 (1.6%) | 2.05 (0.55) |
Grade 8 | 360 | 0.94 (0.71) | 58 (16.1%) | 7 (1.9%) | 2.17 (0.85) |
Grade 9 | 346 | 1.01 (0.75) | 68 (19.7%) | 12 (3.5%) | 2.25 (0.73) |
Grade 10 | 383 | 1.10 (1.02) | 96 (25.1%) | 6 (1.6%) | 2.22 (1.48) |
Grade 11 | 373 | 1.09 (0.89) | 83 (22.3%) | 14 (3.8%) | 2.29 (0.86) |
Grade 12 | 403 | 1.06 (0.83) | 82 (20.4%) | 15 (3.7%) | 2.26 (1.06) |
Grade levels | P < 0.0001 | P < 0.0001 | P = 0.03 | P = 0.66 | |
Kindergarten | 381 | 0.66 (0.58) | 29 (7.6%) | 3 (0.8%) | 2.16 (0.91) |
Elementary school (grade 1–6) | 2179 | 0.75 (0.63) | 207 (9.5%) | 40 (1.8%) | 2.22 (0.86) |
Middle school (grade 7–9) | 1082 | 0.95 (0.69) | 183 (16.9%) | 25 (2.3%) | 2.16 (0.72) |
High school (grade 10–12) | 1159 | 1.08 (0.90) | 261 (22.5%) | 35 (3.0%) | 2.25 (1.18) |
School location | P < 0.0001 | P = 0.0001 | P = 0.29 | P = 0.64 | |
Urban | 2691 | 0.91 (0.76) | 427 (15.9%) | 63 (2.3%) | 2.20 (1.00) |
Rural | 2110 | 0.82 (0.69) | 253 (12.0%) | 40 (1.9%) | 2.24 (0.91) |
Spherical equivalent of more astigmatic eye (diopters) | P < 0.0001 | P < 0.0001 | P < 0.0001 | P = 0.008 | |
≤ −6 | 351 | 1.67 (1.26) | 174 (49.6%) | 33 (9.4%) | 2.46 (1.36) |
> −6, ≤ −5 | 267 | 1.23 (0.81) | 75 (28.1%) | 12 (4.5%) | 2.21 (0.87) |
> −5, ≤ −4 | 414 | 1.07 (0.66) | 90 (21.7%) | 10 (2.4%) | 2.05 (0.61) |
> −4, ≤ −3 | 510 | 0.96 (0.68) | 84 (16.5%) | 10 (2.0%) | 2.12 (0.84) |
> −3, ≤ −2 | 584 | 0.78 (0.61) | 54 (9.3%) | 7 (1.2%) | 2.18 (0.93) |
> −2, ≤ −1 | 768 | 0.75 (0.61) | 67 (8.7%) | 14 (1.8%) | 2.26 (0.79) |
> −1, ≤ −0.5 | 557 | 0.68 (0.47) | 35 (6.3%) | 3 (0.5%) | 1.96 (0.52) |
> −0.5, < 0.5 | 1076 | 0.62 (0.47) | 48 (4.5%) | 6 (0.7%) | 2.05 (0.78) |
≥ 0.5, < 1.0 | 171 | 0.69 (0.56) | 20 (11.7%) | 0 (0.0%) | 1.87 (0.42) |
≥ 1.0 | 103 | 1.23 (0.92) | 33 (32.0%) | 8 (7.8%) | 2.32 (0.72) |
Factors associated with cylinder power and prevalence of astigmatism
Multivariate Model 1: without including spherical equivalent* | Multivariate Model 2: including spherical equivalent§ | ||||
---|---|---|---|---|---|
Characteristics | N | Mean Cylinder in diopter (SE) | P-value | Mean Cylinder in diopter (SE) | P-value |
Grade | < 0.0001 | 0.54 | |||
Kindergarten | 381 | 0.66 (0.04) | 0.91 (0.04) | ||
Grade 1 | 331 | 0.65 (0.04) | 0.92 (0.04) | ||
Grade 2 | 366 | 0.70 (0.04) | 0.94 (0.04) | ||
Grade 3 | 371 | 0.72 (0.04) | 0.94 (0.04) | ||
Grade 4 | 367 | 0.71 (0.04) | 0.93 (0.04) | ||
Grade 5 | 376 | 0.79 (0.04) | 0.94 (0.04) | ||
Grade 6 | 368 | 0.90 (0.04) | 1.01 (0.04) | ||
Grade 7 | 376 | 0.90 (0.04) | 0.98 (0.04) | ||
Grade 8 | 360 | 0.93 (0.04) | 0.97 (0.04) | ||
Grade 9 | 346 | 1.01 90.04) | 1.01 (0.04) | ||
Grade 10 | 383 | 1.09 (0.04) | 1.02 (0.04) | ||
Grade 11 | 373 | 1.06 (0.04) | 0.98 (0.04) | ||
Grade 12 | 403 | 1.04 (0.04) | 0.93 (0.04) | ||
Gender | < 0.0001 | < 0.0001 | |||
Male | 2647 | 0.91 (0.01) | 1.01 (0.02) | ||
Female | 2154 | 0.81 (0.02) | 0.91 (0.02) | ||
School location | 0.10 | 0.18 | |||
Urban | 2691 | 0.88 (0.02) | 0.97 (0.02) | ||
Rural | 2110 | 0.84 (0.01) | 0.95 (0.02) | ||
Spherical equivalent of more astigmatic eye (Diopters) | < 0.0001 | ||||
≤ −6 | 351 | 1.64 (0.04) | |||
> −6, ≤ −5 | 267 | 1.21 (0.04) | |||
> −5, ≤ −4 | 414 | 1.04 (0.04) | |||
> −4, ≤ −3 | 510 | 0.94 (0.03) | |||
> −3, ≤ −2 | 584 | 0.77 (0.03) | |||
> −2, ≤ −1 | 768 | 0.74 (0.03) | |||
> −1, ≤ −0.5 | 557 | 0.68 (0.03) | |||
> −0.5, < 0.5 | 1076 | 0.63 (0.02) | |||
≥ 0.5, < 1.0 | 171 | 0.71 (0.06) | |||
≥ 1.0 | 103 | 1.23 (0.07) |
Multivariate Model 1: without including spherical equivalent * | Multivariate Model 2: including spherical equivalent§ | |||
---|---|---|---|---|
Characteristics | Odds ratio (95% CI) | P-value | Odds ratio (95% CI) | P-value |
Grade | < 0.0001 | 0.65 | ||
Kindergarten | Reference | Reference | ||
Grade 1 | 1.08 (0.63, 1.87) | 1.13 (0.64, 2.00) | ||
Grade 2 | 0.94 (0.54, 1.64) | 0.91 (0.51, 1.62) | ||
Grade 3 | 1.09 (0.64, 1.85) | 0.96 (0.55, 1.68) | ||
Grade 4 | 1.03 (0.60, 1.77) | 0.94 (0.53, 1.68) | ||
Grade 5 | 1.55 (0.94, 2.56) | 1.05 (0.60, 1.81) | ||
Grade 6 | 2.16 (1.35, 3.55) | 1.26 (0.74, 2.15) | ||
Grade 7 | 2.22 (1.38, 3.55) | 1.16 (0.67, 1.95) | ||
Grade 8 | 2.37 (1.48, 3.81) | 1.07 (0.61, 1.79) | ||
Grade 9 | 3.06 (1.92, 4.85) | 1.26 (0.73, 2.10) | ||
Grade 10 | 4.06 (2.60, 6.35) | 1.41 (0.82, 2.31) | ||
Grade 11 | 3.55 (2.26, 5.59) | 1.15 (0.69, 1.96) | ||
Grade 12 | 2.98 (1.89, 4.69) | 0.90 (0.74, 1.07) | ||
Gender | < 0.0001 | < 0.0001 | ||
Male | 1.50 (1.27, 1.78) | 1.65 (1.39,1.98) | ||
Female | Reference | Reference | ||
School location | 0.11 | 0.18 | ||
Urban | 1.15 (0.97, 1.38) | 1.14 (0.94, 1.36) | ||
Rural | Reference | Reference | ||
Spherical equivalent of more astigmatic eye (Diopters) | < 0.0001 | |||
≤ −6 | 20.3 (13.5, 30.6) | |||
> −6, ≤ −5 | 8.05 (5.18, 12.7) | |||
> −5, ≤ −4 | 5.48 (3.68, 8.47) | |||
> −4, ≤ −3 | 4.00 (2.69, 6.10) | |||
> −3, ≤ −2 | 2.12 (1.45, 3.42) | |||
> −2, ≤ −1 | 2.05 (1.39, 3.10) | |||
> −1, ≤ −0.5 | 1.42 (0.90, 2.24) | |||
> −0.5, < 0.5 | Reference | |||
≥ 0.5, < 1.0 | 2.94 (1.69, 5.12) | |||
≥ 1.0 | 10.3 (6.16, 17.1) |
Multivariate Model 1: without including spherical equivalent * | Multivariate Model 2: including spherical equivalent§ | |||
---|---|---|---|---|
Characteristics | Odds ratio (95% CI) | P-value | Odds ratio (95% CI) | P-value |
Grade | 0.04 | 0.17 | ||
Kindergarten | Reference | Reference | ||
Grade 1 | 3.15 (0.83, 12.0) | 3.11 (0.80, 11.9) | ||
Grade 2 | 1.79 (0.42, 7.53) | 1.61 (0.37, 6.97) | ||
Grade 3 | 1.41 (0.31, 6.33) | 1.13 (0.24, 5.29) | ||
Grade 4 | 2.55 (0.65, 9.95) | 2.04 (0.49, 8.47) | ||
Grade 5 | 1.45 (0.32, 6.63) | 0.78 (0.16, 3.78) | ||
Grade 6 | 4.33 (1.21, 15.5) | 2.03 (0.52, 7.80) | ||
Grade 7 | 2.11 (0.52, 8.47) | 0.86 (0.19, 3.83) | ||
Grade 8 | 2.56 (0.66, 9.97) | 0.86 (0.20, 3.72) | ||
Grade 9 | 4.69 (1.31, 16.8) | 1.47 (0.36, 5.91) | ||
Grade 10 | 2.05 (0.51, 8.32) | 0.48 (0.11, 2.19) | ||
Grade 11 | 5.23 (1.48, 18.4) | 1.22 (0.30, 4.87) | ||
Grade 12 | 4.71 (1.34, 3.12) | 1.05 (0.26, 4.18) | ||
Gender | 0.001 | 0.0004 | ||
Male | 2.03 (1.32, 3.12) | 2.21 (1.43, 3.42) | ||
Female | Reference | Reference | ||
School location | 0.63 | 0.69 | ||
Urban | 1.11 (0.73, 1.68) | 1.09 (0.71, 1.66) | ||
Rural | Reference | Reference | ||
Spherical equivalent of more astigmatic eye (Diopters) | < 0.0001 | |||
≤ −6 | 29.6 (10.7, 82.2) | |||
> −6, ≤ −5 | 13.3 (4.39, 40.2) | |||
> −5, ≤ −4 | 6.37 (2.59, 24.7) | |||
> −4, ≤ −3 | 5.19 (1.72, 15.7) | |||
> −3, ≤ −2 | 2.83 (0.89, 9.01) | |||
> −2, ≤ −1 | 4.14 (1.52, 11.2) | |||
> −1, ≤ −0.5 | 1.03 (0.25, 4.17) | |||
> −0.5, < 0.5 | Reference | |||
≥ 0.5 | 5.44 (1.86, 15.9) | |||
AUC = 0.66 (0.61, 0.72) | AUC = 0.79 (0.74, 0.83) |
Factors associated with type and severity of astigmatism
Type of astigmatism | |||||
---|---|---|---|---|---|
Demographics | # of students with astigmatism | With-the-rule n (%) | Against-the-rule n (%) | Oblique n (%) | P-value |
Age (years) | 0.37 | ||||
≤ 6 | 25 | 20 (80%) | 2 (8%) | 3 (12%) | |
7 | 25 | 22 (88%) | 1 (4%) | 2 (8%) | |
8 | 27 | 23 (85%) | 0 (0%) | 4 (15%) | |
9 | 30 | 27 (90%) | 1 (3%) | 2 (7%) | |
10 | 24 | 23 (96%) | 0 (0%) | 1 (4%) | |
11 | 40 | 32 (80%) | 0 (0%) | 8 (20%) | |
12 | 54 | 47 (87%) | 0 (0%) | 7 (13%) | |
13 | 56 | 48 (86%) | 0 (0%) | 8 (14%) | |
14 | 56 | 47 (84%) | 0 (0%) | 9 (16%) | |
15 | 67 | 57 (85%) | 0 (0%) | 10 (15%) | |
16 | 93 | 81 (87%) | 1 (1%) | 11 (12%) | |
17 | 76 | 65 (86%) | 3 (3%) | 9 (12%) | |
18 | 85 | 66 (78%) | 4 (5%) | 15 (18%) | |
≥ 19 | 22 | 17 (77%) | 0 (0%) | 5 (23%) | |
Grade | 0.39 | ||||
Kindergarten | 29 | 24 (83%) | 2 (7%) | 3 (10%) | |
Grade 1 | 27 | 23 (85%) | 1 (4%) | 3 (11%) | |
Grade 2 | 26 | 22 (85%) | 1 (4%) | 3 (11%) | |
Grade 3 | 30 | 28 (93%) | 0 (0%) | 2 (7%) | |
Grade 4 | 28 | 25 (89%) | 0 (0%) | 3 (11%) | |
Grade 5 | 41 | 35 (85%) | 0 (0%) | 6 (15%) | |
Grade 6 | 55 | 45 (82%) | 0 (0%) | 10 (18%) | |
Grade 7 | 57 | 50 (88%) | 0 (0%) | 7 (12%) | |
Grade 8 | 58 | 50 (86%) | 0 (0%) | 8 (14%) | |
Grade 9 | 68 | 58 (85%) | 1 (1%) | 9 (13%) | |
Grade 10 | 96 | 83 (86%) | 1 (1%) | 12 (13%) | |
Grade 11 | 83 | 72 (86%) | 1 (1%) | 10 (12%) | |
Grade 12 | 82 | 60 (73%) | 4 (5%) | 18 (22%) | |
Gender | 0.09 | ||||
Male | 427 | 371 (87%) | 6 (1%) | 50 (12%) | |
Female | 253 | 204 (81%) | 5 (2%) | 44 (17%) | |
School location | 0.34 | ||||
Urban | 427 | 356 (84%) | 6 (1%) | 65 (15%) | |
Rural | 253 | 219 (87%) | 5 (2%) | 29 (11%) | |
Spherical equivalent of more astigmatic eye (Diopters) | 0.78 | ||||
≤ −6 | 174 | 145 (83%) | 2 (1%) | 27 (16%) | |
> −6, ≤ −5 | 75 | 59 (79%) | 1 (1%) | 15 (20%) | |
> −5, ≤ −4 | 90 | 74 (82%) | 1 (1%) | 15 (17%) | |
> −4, ≤ −3 | 84 | 71 (85%) | 2 (2%) | 11 (13%) | |
> −3, ≤ −2 | 54 | 46 (85%) | 2 (4%) | 7 (13%) | |
> −2, ≤ −1 | 67 | 60 (90%) | 1 (2%) | 6 (9%) | |
> − 1, ≤ −0.5 | 35 | 29 (83%) | 1 (3%) | 5 (14%) | |
> − 0.5, < 0.5 | 48 | 45 (94%) | 1 (2%) | 2 (4%) | |
≥ 0.5, < 1.0 | 20 | 16 (80%) | 1 (5%) | 3 (15%) | |
≥ 1.0 | 33 | 30 (91%) | 0 (0%) | 3 (9%) |
Multivariate Model 1: without including spherical equivalent * | Multivariate Model 2: including spherical equivalent§ | ||||
---|---|---|---|---|---|
Demographics | N | Mean cylinder in diopter (SE) | P-value | Mean cylinder in diopter (SE) | P-value |
Grade | 0.91 | 0.93 | |||
Kindergarten | 29 | 2.14 (0.18) | 2.13 (0.19) | ||
Grade 1 | 27 | 2.31 (0.19) | 2.38 (0.19) | ||
Grade 2 | 26 | 2.12 (0.19) | 2.18 (0.20) | ||
Grade 3 | 30 | 2.14 (0.18) | 2.15 (0.18) | ||
Grade 4 | 28 | 2.24 (0.18) | 2.27 (0.18) | ||
Grade 5 | 41 | 2.03 (0.15) | 2.02 (0.18) | ||
Grade 6 | 55 | 2.34 (0.13) | 2.26 (0.15) | ||
Grade 7 | 57 | 2.03 (0.13) | 1.96 (0.13) | ||
Grade 8 | 58 | 2.15 (0.13) | 2.07 (0.13) | ||
Grade 9 | 68 | 2.23 (0.12) | 2.13 (0.13) | ||
Grade 10 | 96 | 2.21 (0.10) | 2.10 (0.11) | ||
Grade 11 | 83 | 2.29 (0.11) | 2.10 (0.12) | ||
Grade 12 | 82 | 2.24 (0.11) | 2.06 (0.12) | ||
Gender | 0.08 | 0.04 | |||
Male | 427 | 2.26 (0.06) | 2.21 (0.05) | ||
Female | 253 | 2.12 (0.05) | 2.06 (0.06) | ||
School location | 0.57 | 0.57 | |||
Urban | 427 | 2.17 (0.06) | 2.12 (0.06) | ||
Rural | 253 | 2.21 (0.06) | 2.16 (0.07) | ||
Spherical equivalent of more astigmatic eye (diopters) | 0.007 | ||||
≤ −6 | 174 | 2.50 (0.09) | |||
> −6, ≤ −5 | 75 | 2.24 (0.12) | |||
> −5, ≤ −4 | 90 | 2.09 (0.11) | |||
> −4, ≤ −3 | 84 | 2.14 (0.11) | |||
> −3, ≤ −2 | 54 | 2.19 (0.14) | |||
> − 2, ≤ −1 | 67 | 2.25 (0.12) | |||
> −1, ≤ −0.5 | 35 | 1.92 (0.17) | |||
> − 0.5, < 0.5 | 48 | 1.98 (0.14) | |||
≥ 0.5, < 1.0 | 20 | 1.83 (0.22) | |||
≥ 1.0 | 33 | 2.26 (0.17) |