Prevalence and causes of visual impairment and rate of wearing spectacles in schools for children of migrant workers in Shanghai, China

Table 2 Distribution of uncorrected, presenting, and best corrected visual acuity

Visual acuity category	Uncorrected visual acuity	Wearing glasses*	Presenting visual acuity	Best visual acuity
Visual acuity category	n (%; 95% CI)^†	n (%)	n (%; 95% CI)^†	n (%; 95% CI)^†
≥20/32 both eyes	7506 (78.91; 78.09–79.73)	17 (0.23)	7677 (80.71; 79.92–81.50)	9301 (97.78; 97.48–98.08)
≥20/32 one eye only	738 (7.75; 7.21–8.28)	44 (5.96)	764 (8.03; 7.48–8.58)	151 (1.59; 1.34-1.84)
≤20/40 to ≥ 20/63 better eye	887 (9.33; 8.75–9.92)	135 (15.22)	816 (8.58; 8.02–9.14)	43 (0.41; 0.21–0.78)^†
≤20/80 to ≥ 20/160 better eye	333 (3.50; 3.13–3.87)	102 (30.63)	235 (2.34; 1.59–3.42)^†	15 (0.14; 0.07 –0.31)^†
≤20/200 better eye	48 (0.50; 0.33–0.75)^†	30 (62.5)	20 (0.20; 0.11–0.38)^†	2 (0.03; 0.004–0.19)^†
All	9512 (100.00)	328 (3.45)	9512 (100.00)	9512 (100.00)

*The percentage within each visual acuity category is based on uncorrected vision.
^†Confidence intervals (CIs) were calculated using the exact binomial distribution instead of the normal approximation, and cluster design effects were taken into account in calculating Cls for estimates based on the normal approximation ranging from 1.647 to 6.718.

ISSN: 1471-2458