Table 1. Baseline Demographic and Clinical Characteristics in a Study of the Effect of Low-Concentration Atropine Eyedrops vs Placebo on Myopia Incidence in Children.
| Characteristic | Mean (SD) | ||
|---|---|---|---|
| 0.05% Atropine (n = 160) | 0.01% Atropine (n = 159) | Placebo (n = 155) | |
| Age, y | 6.86 (1.42) | 6.88 (1.35) | 6.75 (1.27) |
| Sex, No. (%) | |||
| Male | 81 (50.6) | 78 (49.1) | 78 (50.3) |
| Female | 79 (49.4) | 81 (50.9) | 77 (49.7) |
| Body mass index | 15.66 (2.60) | 15.58 (2.10) | 15.47 (2.00) |
| Spherical equivalent, Da | 0.50 (0.33) | 0.51 (0.33) | 0.53 (0.31) |
| Axial length, mmb | 22.82 (0.72) | 22.89 (0.70) | 22.80 (0.64) |
| Central corneal thickness, μmc | 556.07 (32.13) | 555.78 (31.58) | 553.14 (31.71) |
| Intraocular pressure, mm Hgd | 15.89 (2.01) | 15.85 (2.00) | 15.97 (1.91) |
| Pupil size, mme | |||
| Photopic | 3.55 (0.57) | 3.57 (0.61) | 3.69 (0.72) |
| Mesopic | 6.36 (0.68) | 6.34 (0.74) | 6.53 (0.74) |
| Accommodation amplitude, Df | 13.34 (2.69) | 13.60 (2.67) | 13.33 (2.74) |
| Visual acuity, logMARg | |||
| Distance | 0.03 (0.09) | 0.02 (0.09) | 0.03 (0.07) |
| Near | 0.04 (0.10) | 0.03 (0.10) | 0.02 (0.09) |
| Outdoor activity, h/dh | 1.48 (0.51) | 1.50 (0.48) | 1.46 (0.48) |
| Near work, D h/di | 10.55 (3.55) | 10.20 (3.64) | 10.54 (3.69) |
| Parents with myopia, No. (%) | |||
| 1 | 66 (37.4) | 62 (39.0) | 58 (41.2) |
| 2 | 94 (62.6) | 97 (61.0) | 97 (58.8) |
| Baseline visit before January 1, 2020, No. (%) | 94 (58.8) | 102 (64.2) | 92 (59.4) |
Spherical equivalent gives an estimate of the refractive error of the eye. It is calculated as spherical power plus half of the cylinder power.
Axial length is the length of the eyeball and a main determining factor for refractive status, with the increased axial length being the major cause of myopia. The mean (SD) axial length in children in Hong Kong is 23.08 (0.92) mm.20
Central corneal thickness (CCT) is the thickness of the central cornea. The mean (SD) CCT of emmetropic eyes in Chinese children is 557.98 (33.77) μm.21
Intraocular pressure is the fluid pressure of the eye. It is a measurement of the force exerted by the aqueous humor on the internal surface area of the anterior eye; reference range, 10-21 mm Hg.
Photopic pupil size is measured under medium to high light conditions and mesopic pupil size is measured under low light conditions. In children aged 4 to 12 years in Hong Kong, the mean (SD) photopic pupil size was 3.75 (0.82) mm and mesopic pupil size was 6.66 (0.69) mm.13
Accommodation amplitude is a measure of the ability of the eye to change the refractive power/curvature of the lens to focus from far to near distances. The mean (SD) accommodation amplitude in Hong Kong among children aged 4 to 12 years was 12.10 (2.48) D.13
Visual acuity is a measure of the vision at a given distance. The normal visual acuity by logMAR values is ≤0.1 (range, 0.1 to −0.2; lower values indicate better visual acuity). Distance and near visual acuity describe the vision at a distance of 6 m and 40 cm.
Outdoor activity includes outdoor exercise plus outdoor leisure activity. An increase in outdoor activities can help delay the onset and progression of myopia in children.
Diopter hours were calculated using the following formula: 3×(homework + reading + playing cell phone) + 2×(using computer + playing video game) + 1×(watching television). This summation represents an attempt to weigh the child's visual activities according to the amount of accommodation in diopters required to perform them. More diopter hours per day may be associated with higher chance of developing myopia.22