Diplopia

Diplopia is double vision. It is a visual disturbance that causes the brain to perceive two images of a single object. Unlike blurred vision, in diplopia the image is perceived clearly, but duplicated.

Depending on how persistently it occurs, diplopia can be classified into two types:

• Constant diplopia: occurs continuously, regardless of the activity being performed. It is considered a medical emergency, especially if accompanied by severe headache, numbness on one side of the face, weakness on one side of the body, difficulty speaking or swallowing, loss of balance, and confusion, as these are characteristic signs of a stroke.
• Intermittent diplopia: occurs temporarily and only at specific times. It requires medical attention as soon as possible, particularly if accompanied by other symptoms, although it is not considered an emergency.

Diplopia negatively affects the patient's quality of life, as it causes confusion and difficulty estimating distances or performing everyday tasks.

Symptoms

The primary symptom of diplopia is double vision, which may present in different ways:

• Types of diplopia according to eye involvement:
  • Monocular diplopia: persists when one eye is closed or covered.
  • Binocular diplopia: the most common form. It occurs when both eyes are open and disappears when either eye is closed.

• Types of diplopia according to image orientation:
  • Horizontal diplopia: the two images appear side by side.
    • Homonymous diplopia: binocular and convergent, meaning both eyes deviate inward.
    • Heteronymous or crossed diplopia: binocular and divergent, meaning the eyes point outward.
  • Vertical diplopia: one image appears above the other.
  • Oblique diplopia: the images appear diagonally duplicated.

In some cases, depending on the underlying cause of diplopia, patients may also experience other symptoms, such as:

• Eye strain: the effort to correct double vision causes ocular fatigue, itching, dryness, photophobia, and headache.
• Blurred vision: loss of visual sharpness.
• Shadow vision: a halo is perceived around images.
• Pain when moving the eyes.
• Difficulty perceiving depth.
• Difficulty estimating distances.
• Ptosis: drooping eyelids.
• Dizziness.
• Nausea.
• Loss of balance.

Causes

The causes of diplopia are highly varied, as it may originate in different organs and systems of the body. The most significant causes include:

• Muscular and nerve disorders (cause binocular diplopia):
  • Strabismus: the eyes are not properly aligned. In children, the brain suppresses the image from the deviated eye, but the adult brain is unable to do so.
  • Paralysis of the cranial nerves that control the eye muscles.
• Neurological and vascular disorders (cause binocular diplopia):
  • Stroke or cerebrovascular accident: blood flow to the brain is reduced or completely interrupted.
  • Multiple sclerosis: chronic inflammatory disease of the central nervous system that disrupts communication between the brain and the rest of the body.
  • Cerebral aneurysm: dilation of the wall of one or more blood vessels in the brain, increasing the risk of rupture.
  • Brain tumor: abnormal growth of a mass of cells in the brain that may be benign or malignant (cancerous).
  • Migraine with aura: unilateral throbbing headache preceded by flashing lights or wavy lines in the visual field.
• Eye disorders: cause monocular diplopia.
  • Severe dry eye: insufficient tear production to adequately lubricate and protect the eye causes the corneal surface to become irregular. As a result, light is not properly focused on the retina and the image becomes duplicated.
  • High astigmatism: the lens or cornea has an irregular curvature, preventing light from focusing on a single point on the retina.
  • Cataracts: lens opacity that may cause abnormal light scattering.
  • Keratoconus: progressive thinning of the cornea, which gradually assumes a cone-like shape.
• Other possible causes:
  • Poorly controlled diabetes: prolonged elevated blood glucose levels damage and obstruct the blood vessels of the eyes, causing the optic nerve to no longer receive the oxygen it needs (ischemia) to function properly.
  • Hypertension: persistently high blood pressure hardens small arteries and may cause ischemia of the ocular nerves.
  • Graves-Basedow disease: an autoimmune disorder causing hyperthyroidism (overactivity of the thyroid gland), which leads to inflammation of the eye muscles and accumulation of substances in the tissues behind the eyes.
  • Traumatic brain injury: a blow to the head can damage the muscles and nerves responsible for eye movement.
  • Myasthenia gravis: an autoimmune disease that causes muscle weakness, including weakness of the eye muscles.

Risk Factors

The main risk factors for diplopia include:

• Diabetes: a metabolic disease in which the body does not properly regulate blood sugar levels. It may result from insulin deficiency or ineffective insulin function.
• Hypertension: blood exerts excessive force against the walls of blood vessels.
• Arteriosclerosis: fatty and cholesterol plaques form within artery walls, reducing blood flow.
• Cardiovascular disease: disorders affecting the heart and blood vessels.
• Muscle imbalance.
• Advanced age: aging increases the likelihood of vascular disease and degenerative conditions affecting the lens or retina. Therefore, diplopia is more common in older adults.
• Use of toxic substances.
• Alcoholism: weakens the central nervous system and causes poor coordination of the muscles responsible for eye movements.
• Stress: accumulated tension and fatigue may cause transient diplopia.
• Head trauma.

Complications

The most common complications of diplopia include:

• General discomfort.
• Irritability.
• Chronic visual fatigue.
• Frequent headaches.
• Spatial disorientation.
• Loss of balance.
• Falls.
• Social isolation.
• Work disability.
• Anxiety.
• Chronic neck and back pain: caused by involuntarily tilting or turning the head in an attempt to align the images.

Which specialist treats diplopia?

Diplopia is primarily managed within the specialty of Ophthalmology. In some cases, Neurology involvement is also required.