Table 2.
Magnitude of cylinder power and prevalence rate of astigmatism by characteristics of students (N = 4804)
| 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) |