diplopía

Diplopía, or diplopia, is the perception of two images of a single object. It can be monocular, persisting when one eye is closed, or binocular, occurring only when both eyes are open and usually resolving when one eye is closed. Monocular diplopia typically points to a problem within the affected eye—such as refractive error, cataract, corneal irregularity, or dry eye. Binocular diplopia results from misalignment of the eyes and commonly reflects ocular motor dysfunction or neurological disease.

Common binocular causes include strabismus, and palsies of the third, fourth, or sixth cranial nerves, thyroid eye disease, myasthenia gravis, orbital pathology, or traumatic injury to the extraocular muscles. Less frequent causes include brainstem or cerebellar lesions, aneurysms, or tumors. Diplopia can be constant or intermittent and may vary with gaze, fatigue, or lighting.

Evaluation begins with a thorough history and ocular examination. Key components are refraction to exclude refractive error, cover tests to assess alignment, measurement of extraocular movement, and diplopia mapping. Fundoscopic examination and pupil testing are standard. If vascular risk, neurologic signs, severe headache, fever, or focal deficits are present, imaging with MRI or CT and neurologic consultation are indicated. Laboratory workup may target diabetes, thyroid disease, autoimmune conditions, or myasthenia gravis.

Management depends on the underlying cause. Monocular diplopia is typically corrected with appropriate refractive correction, cataract treatment, or management of corneal surface disease. Binocular diplopia is often managed with prisms in glasses, occlusion, or, when appropriate, strabismus surgery. Acute diplopia with sudden onset or concerning neurologic symptoms requires urgent evaluation.

Prognosis varies by etiology; many cases due to benign refractive error or transient cranial nerve palsy improve with treatment or time, while others related to vascular or neuromuscular disease require ongoing care.