Chapter 584

Vision is an essential sensory input from infancy and throughout childhood that allows for normal physical, cognitive, educational, and social development and for adult occupational training. Vision is present at birth at approximately a 20/200 level. Visual acuity develops rapidly during the first year, with normal acuity reached by 9 to 12 months of age. Blindness or visual impairment can be assessed in terms of the level of visual function and by scoring functional vision related to quality-of-life achievements. Assessment of visual acuity is the most often used parameter for estimating vision. The assessment of visual acuity in young children is imprecise. Therefore, it is necessary to define ranges of visual loss. Also test results may improve with advancing age and development. Levels of visual function, ranging from normal to visually impaired, have been categorized into five levels of performance (Table 584-1).

Table 584-1. Visual Function Based on Levels of Visual Acuity

Unsteady eye movements may be evidence of poor vision since birth or with early onset before 2 years of age. When related to an ocular etiology such as cataracts, retinal abnormalities, or optic nerve defects, a pendular nystagmus is often present, which becomes a characteristic jerk nystagmus in lateral gaze. A jerk nystagmus demonstrates a slow-conjugate drift in one direction followed by a rapid-corrective return to fixation. If the vision is very poor, the abnormal eye movements are also conjugate but become more random in many planes and are less sustained. This is sometimes referred to as “wandering eye movements.” In the unique case of neuroblastoma, children may have a very disorganized rapid pattern of eye movements, often brought on by startle stimuli, known as opsoclonus. Infantile sensory nystagmus may be seen with extreme vision loss in only one eye, but in this setting is characteristically only jerk in type. In addition to infantile sensory nystagmus, other causes of nystagmus must be distinguished and include disturbances of motor origin. Congenital motor nystagmus is usually idiopathic but may also be seen as a hereditary disorder found in various Mendelian patterns. It is important to recognize the significance of early onset nystagmus as a key sign of vision loss since infancy. This nystagmus may lessen with visual improvement or with aging.

It has been estimated that there are 1.5 million blind children worldwide and that 90% live in developing countries. Of the estimated 500,000 children ...

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