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Senses
Hearing and vision disorders occur in more than half of people with Down syndrome.

Ocular findings in Down Syndrome
Brushfield spots (small white or grayish/brown spots on the periphery of the iris), upward slanting palpebral fissures (the opening between the upper and lower lids) and epicanthal folds (folds of skin between the upper eyelid and the nose) are clinical signs at birth suggesting the diagnosis of Down syndrome especially in the Western World. None of these requires treatment.

Visually significant congenital cataracts (clouding of the lens of the eye) occur more frequently with Down syndrome. Neonates with Down syndrome should be screened for cataract because early recognition and referral reduce the risk of vision loss from amblyopia. Dot-like opacities in the cortex of the lens (cerulean cataract) are present in up to 50% of people with Down syndrome, but may be followed without treatment if they are not visually significant.

Strabismus, nystagmus and nasolacrimal duct obstruction occur more frequently in children with Down syndrome. Screening for these diagnoses should begin within six months of birth. Strabismus is more often acquired than congenital. Early diagnosis and treatment of strabismus reduces the risk of vision loss from amblyopia. In Down syndrome, the presence of epicanthal folds may give the false impression of strabismus, referred to as pseudostabismus. Nasolacrimal duct obstruction, which causes tearing (epiphora), is more frequently bilateral and multifactorial than in children without Down syndrome.

Refractive error is more common with Down syndrome, though the rate may not differ until after twelve months of age compared to children without Down syndrome. Early screening is recommended to identify and treat significant refractive error with glasses or contact lenses. Poor accommodation (ability to focus on close objects) is associated with Down syndrome, which may mean bifocals are indicated.

In keratoconus, the cornea progressively thins and bulges into a cone shape, causing visual blurring or distortion. Keratoconus first presents in the teen years and progresses into the thirties. Down syndrome is a strong risk factor for developing keratoconus, and onset may be occur at a younger age than in those without Down syndrome. Eye rubbing is also a risk factor for developing keratoconus. It is speculated that chronic eye irritation from blepharitis may increase eye rubbing in Down syndrome, contributing to the increased prevalence of keratoconus.

An association between glaucoma and Down syndrome is often cited. Glaucoma in children with Down syndrome is uncommon, with a prevalence of less than 1%. It is currently unclear if the prevalence of glaucoma in children or adults with Down syndrome differs from that in the absence of Down syndrome.