Causes of Severe Visual Impairment and Blindness in the School for the Blind in Ahvaz

To determine the anatomical sites and causes of severe visual impairment (SVI) and blindness in children attending a school for the blind in Ahvaz. In this case series study, all 51 students of the only school for the blind in Ahvaz were examined by two ophthalmologists. Blindness and SVI were defined according to the World Health Organization (WHO) criteria as visual acuity less than 3/60 and 6/60, respectively. Visual acuity was measured by snellen chart; slit lamp biomicroscopy and dilated fundus exam were performed for all children. Of 51 examined students aged 7 to 16 years, one child was not visually handicapped and therefore excluded. Causes of blindness and SVL in 50 students (100 eyes) in order of frequency were: optic atrophy 7 (14%), retinitis pigmentosa 7 (14%), chorioretinal coloboma 6 (12%), severe myopia 4 (8%), macular dystrophy 4 (8%), old retinal detachment 1 (2%), cataract 5 (10%), microcornea 6 (12%), corneal opacity 4 (8%), persistent hyperplastic primary vitreous (PHPV) 1 (2%) and hypotonia and phthysis bulbi 5 (10%). The most common causes of SVI and blindness were rare inheritable causes including congenital disease of the retina, optic nerve and cornea which resembles the pattern of childhood blindness in developed countries.