Double vision, known medically as diplopia, is the perception of seeing two images of a single object. This symptom occurs when the eyes, muscles, nerves, and brain fail to work in harmony to produce one unified image. Double vision in a child is a symptom, not a diagnosis, and requires prompt medical evaluation to determine the underlying cause, which can range from simple vision problems to serious neurological issues.
Problems with Eye Muscle Coordination
The most frequent cause of double vision in children involves a problem with the physical alignment and movement of the eyes, often termed binocular diplopia. This type of double vision vanishes when the child covers one eye because the misalignment is only apparent when both eyes are open. When the eyes fail to point precisely at the same object, the brain receives conflicting visual information, preventing the fusion of the two images into one.
Strabismus, commonly referred to as crossed or misaligned eyes, is the most prevalent cause in this category. This condition involves the eyes turning inward (esotropia), outward (exotropia), upward (hypertropia), or downward (hypotropia). While the brain in very young children often learns to suppress the image from the misaligned eye, older children with a sudden or decompensated misalignment may experience diplopia.
Another element is decompensated phorias, where a latent tendency for the eyes to misalign suddenly becomes visible. This can be triggered by illness, fatigue, or stress, weakening the visual system’s ability to maintain alignment. Also, a physical restriction of the eye movement apparatus, such as from trauma or inflammation affecting the orbital socket or the eye muscles, can mechanically prevent the eye from moving into the correct position.
Central Nervous System and Nerve Issues
Double vision can also signal a disruption in the “wiring” or “control center” that manages eye movement, involving the cranial nerves or the brain itself. Three specific cranial nerves—the oculomotor (III), trochlear (IV), and abducens (VI)—control the six muscles that move each eye. Damage or compression to any of these nerves results in a cranial nerve palsy, leading to muscle weakness or paralysis and misalignment.
An acute third cranial nerve palsy, for instance, can cause the eyelid to droop (ptosis) and the eye to drift outward and downward, often representing a serious neurological event that requires urgent evaluation. Fourth cranial nerve palsy specifically affects the superior oblique muscle, causing vertical double vision that is sometimes compensated for by the child tilting their head. Sixth cranial nerve palsy limits the eye’s ability to turn outward, causing a horizontal double image that worsens when looking in the direction of the affected nerve.
Trauma to the head, such as a concussion or a severe head injury, can directly damage these nerves or cause swelling within the brain, leading to temporary or persistent diplopia. Space-occupying lesions like tumors, abscesses, or hydrocephalus (excess fluid) can exert pressure on the brainstem or the cranial nerves as they exit the brain. The sudden onset of double vision due to this pressure disrupts neurological signals and necessitates immediate and thorough investigation.
Underlying Health Conditions and Infections
In some cases, double vision is not a primary eye or brain issue but a symptom of a larger, systemic health problem affecting the body’s nerves or muscles. Certain autoimmune disorders target the communication between nerves and muscles, which can manifest as eye misalignment. Myasthenia Gravis, for example, is an autoimmune condition where the body attacks the receptors that receive nerve signals, leading to fluctuating muscle weakness that often affects the eye muscles first.
Thyroid disorders, particularly Graves’ ophthalmopathy, can cause inflammation and swelling of the tissues and muscles around and behind the eyes, mechanically restricting movement and causing double vision. Certain infections, such as those causing meningitis, can lead to inflammation around the brain and nerves, potentially resulting in a temporary cranial nerve palsy and diplopia. Early-onset diabetes, by affecting the small blood vessels that supply the cranial nerves, can also cause a sudden nerve palsy and double vision, though this is rare in children.
Medical Evaluation and Emergency Signs
Any instance of double vision in a child, whether constant or intermittent, warrants an immediate consultation with a pediatrician or eye care professional. The evaluation begins with a detailed history, including whether the double vision is present in one eye (monocular) or disappears when one eye is covered (binocular). Diagnostic steps include a comprehensive vision test, assessment of eye alignment and movement, and a full neurological examination. Depending on the suspected cause, further testing may involve blood work or imaging studies like a Computed Tomography (CT) scan or Magnetic Resonance Imaging (MRI) to visualize the brain and surrounding structures. Early treatment is essential for preventing long-term vision issues.
Certain accompanying signs are considered “red flags” that require an immediate trip to the emergency room. Urgent medical attention is necessary if double vision is accompanied by signs of a serious neurological event, including:
- Sudden onset paired with a severe headache.
- Persistent nausea or vomiting.
- Neck stiffness or any sign of altered consciousness or confusion.
- Weakness, slurred speech, or unequal pupil size.
- Double vision following any head injury.