Table 1. Causes of visual impairment.

Causes of VI	Students with VI (one or both eyes)	Prevalence in the population n=3654 (%)
Refractive error	3286 (95.63)	89.92
Amblyopia	36 (1.05)	0.99
Congenital cataract	20 (0.58)	0.55
Retinal atrophy or degeneration	24 (0.70)	0.66
Strabismus	10 (0.29)	0.27
Congenital nystagmus	6 (0.17)	0.16
Surgery and orthokeratology	54 (1.57)	1.48
Total	3436 (100)	94.03

n (%)