Table 1. Prevalence of visual impairment (low vision and blindness) by age and gender.

	Presenting visual acuity				Best corrected visual acuity
	n	Low vision	Blindness	Visual impairment	n	Low vision	Blindness	Visual impairment
		% (95% CI)	% (95% CI)	% (95% CI)		% (95% CI)	% (95% CI)	% (95% CI)
Age groups
40–44	960	1.5 (0.7–2.3)	0.1 (0.01–0.7)a	1.6 (0.7–2.4)	960	0.2 (0.05–0.8)a	0	0.2 (0.1–0.8)a
45–49	1389	0.9 (0.4–1.4)	0.6 (0.2–1.0)	1.5 (0.8–2.2)	1388	0.3 (0.0–0.6)	0.4 (0.0–0.7)	0.6 (0.2–1.1)
50–54	1285	1.5 (0.8–2.2)	0.5 (0.1–0.9)	2.0 (1.2–2.8)	1285	0.4 (0.0–0.7)	0.2 (0.0–0.5)	0.6 (0.2–1.1)
55–59	953	1.9 (1.0–2.8)	0.7 (0.2–1.3)	2.6 (1.6–3.7)	953	0.8 (0.3–1.4)	0.3 (0.0–0.7)	1.2 (0.5–1.8)
60–64	601	4.5 (2.9–6.1)	0.8 (0.1–1.6)	5.3 (3.6–7.0)	600	1.3 (0.4–2.2)	0.3 (0.08–1.3)a	1.7 (0.6–2.7)
Gender
Male	2212	1.3 (0.8–1.7)	0.6 (0.3–1.0)	1.9 (1.3–2.5)	2211	0.5 (0.2–0.8)	0.3 (0.1–0.5)	0.8 (0.4–1.2)
Female	2976	2.1 (1.6–2.6)	0.5 (0.2–0.7)	2.6 (2.0–3.1)	2975	0.5 (0.3–0.8)	0.2 (0.0–0.4)	0.7 (0.4–1.0)
Crude total	5188	1.8 (1.4–2.1)	0.5 (0.3–0.7)	2.3 (1.9–2.7)	5186	0.5 (0.3–0.7)	0.3 (0.1–0.4)	0.8 (0.5–1.0)
Age standardizedb
Male	2212	1.2 (0.8–1.7)	0.6 (0.3–1.0)	1.8 (1.2–2.5)	2211	0.5 (0.2–0.8)	0.3 (0.1–0.5)	0.8 (0.4–1.2)
Female	2976	2.0 (1.5–2.5)	0.4 (0.2–0.6)	2.4 (1.9–2.9)	2975	0.5 (0.2–0.7)	0.2 (0.0–0.3)	0.6 (0.4–0.9)
Age and gender standardized totalb	5188	1.6 (1.3–2.0)	0.5 (0.3–0.7)	2.1 (1.7–2.5)	5186	0.5 (0.3–0.7)	0.2 (0.1–0.4)	0.7 (0.5–0.9)
Design effect		0.95	0.92	1.03		0.91	0.96	0.97

Abbreviation: CI, confidence interval.

^a95% CI calculated by binomial distribution.

^bThe Shahroud population is considered as the standard population.