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Cortical blindness is the total or partial loss of vision in a normal-appearing eye caused by damage to the brain's occipital cortex. [1] Cortical blindness can be acquired or congenital, and may also be transient in certain instances. [2]
CVI is also sometimes known as cortical blindness, although most people with CVI are not totally blind. The term neurological visual impairment (NVI) covers both CVI and total cortical blindness. Delayed visual maturation, another form of NVI, is similar to CVI, except the child's visual difficulties resolve in a few months.
Childhood blindness is most prevalent among children with genetic ancestry from Africa and Asia, who represent 75% of the world's affected population. [ 13 ] [ 32 ] A 2014 review indicated that an estimated 238,500 children with bilateral blindness (rate 1.2/1,000) live in the Eastern Mediterranean region. [ 30 ]
Congenital blindness is a hereditary disease and can be treated by gene therapy. Visual loss in children or infants can occur either at the prenatal stage (during the time of conception or intrauterine period) or postnatal stage (immediately after birth). [3] There are multiple possible causes of congenital blindness.
Cortical blindness refers to any partial or complete visual deficit that is caused by damage to the visual cortex in the occipital lobe. Unilateral lesions can lead to homonymous hemianopias and scotomas. Bilateral lesions can cause complete cortical blindness and can sometimes be accompanied by a condition called Anton-Babinski syndrome. [26]
Treatment options depend on the severity of the condition. For children under the age of two years old whose vision is affected by the cataracts in both eyes, surgical options include intraocular lens implantation or a lensectomy. [2] Congenital cataracts are considered to be a significant cause of childhood blindness.
In children, early diagnosis and treatment of impaired visual system function is an important factor in ensuring that key social, academic and speech/language developmental milestones are met. Cataract is clouding of the lens, which in turn affects vision.
The vision of infants under one month of age ranges from 6/240 to 6/60 (20/800 to 20/200). [4] By two months, visual acuity improves to 6/45 (20/150). By four months, acuity improves by a factor of 2 – calculated to be 6/18 (20/60) vision. As the infant grows, the acuity reaches the healthy adult standard of 6/6 (20/20) at six months. [5]