Accommodation

Definition

Accommodation is the physiologic process by which the lens of the eye changes shape to focus images on the retina. When shifting gaze from far to near objects, the ciliary muscle contracts, the lens becomes more spherical, and the pupils constrict.

Assessment

Accommodation is evaluated as the 'A' in PERRLA: Pupils Equal, Round, Reactive to Light, and Accommodation. The examiner asks the patient to focus on a distant object, then on an object held 10 to 15 cm from the nose. Normal response is pupillary constriction and convergence of the eyes.

Clinical Significance

Loss of accommodation (presbyopia) occurs normally with aging as the lens stiffens. Pathologic loss may indicate cranial nerve III (oculomotor) dysfunction, brainstem injury, or drug effects such as anticholinergics. A non-reactive pupil is a late and ominous sign of increased intracranial pressure.

Nursing Considerations

Include accommodation in neurologic assessments for patients with head injury, stroke, or altered mental status, such as document pupil size (in mm), shape, and reactivity symmetrically. Report new unilateral fixed pupil immediately. It may indicate uncal herniation.

NCLEX Relevance

Tested in cranial nerve assessment and neuro checks. Differentiate benign age-related presbyopia from acute neurologic emergencies.