Chapter 612 Abnormalities of Refraction and Accommodation
Hyperopia
In hyperopia, accommodation is used to bring objects into focus for both far and near gaze. If the accommodative effort required is not too great, the child has clear vision and is comfortable with both distant and close work. In high degrees of hyperopia requiring greater accommodative effort, vision may be blurred, and the child might complain of eyestrain, headaches, or fatigue. Squinting, eye rubbing, and lack of interest in reading are common manifestations. If the induced discomfort is great enough, a child might not make an effort to see well and can develop bilateral amblyopia (ametropic amblyopia). Esotropia may also be associated (see the discussion of convergent strabismus, accommodative esotropia in Chapter 615).
Accommodation
Differential diagnosis includes tumors, degenerative diseases, vascular lesions, trauma, and infectious diseases. Systemic disorders that can cause impairment of accommodation include botulism, diphtheria, Wilson disease, diabetes mellitus, and syphilis. Adie tonic pupil can also lead to a deficiency of accommodation after some viral illnesses (Chapter 614). An apparent defect in accommodation may be psychogenic in origin; it is common for a child to feign inability to read when it can be demonstrated that visual acuity and ability to focus are normal.
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