Double vision, or diplopia, occurs when a person sees two images of a single object, which can be horizontal, vertical, or diagonal. It can affect one eye (monocular diplopia) or both eyes (binocular diplopia), with different causes for each type.

Causes of Double Vision

1. Eye-related causes (Monocular diplopia):

• Problems with the cornea (the clear front layer of the eye) such as irregularities, scars, infections, or dryness.
• Lens issues like cataracts, which cloud the normally clear lens.
• Refractive errors or uncorrected vision problems.
  These causes affect vision in one eye and the double vision persists even when the other eye is closed

2. Muscle and nerve-related causes (Binocular diplopia):

• Misalignment of the eyes (strabismus), where the eyes do not look in the same direction.
• Damage or dysfunction of the muscles controlling eye movement or the nerves supplying them, such as from myasthenia gravis (an autoimmune disorder), thyroid eye disease (Graves' disease), or diabetes-related nerve damage.
• Neurological conditions like multiple sclerosis, Guillain-Barre syndrome, or cranial nerve palsies.
• Trauma or injury affecting the eye muscles or nerves.
• Systemic diseases affecting nerves or muscles

3. Brain-related causes:

• Stroke or transient ischemic attack (TIA), which can impair nerves controlling eye muscles.
• Brain tumors or aneurysms pressing on nerves or brain areas that coordinate vision.
• Increased intracranial pressure from injury, bleeding, or infection.
• Migraines with visual disturbances.
  These causes typically produce binocular diplopia that resolves when one eye is closed

4. Temporary causes:

• Fatigue, stress, intoxication, low blood sugar, or standing up too quickly can cause brief episodes of double vision.
• Infections like shingles affecting the eye area.
  While often less serious, these should be evaluated if persistent or recurrent

Summary

Double vision can arise from a variety of causes involving the eye structures, muscles, nerves, or brain. Monocular double vision usually indicates an eye problem, while binocular double vision often points to muscle, nerve, or brain issues. Causes range from minor (e.g., astigmatism, fatigue) to serious and potentially life-threatening conditions (e.g., stroke, aneurysm, brain tumor), so sudden or persistent double vision warrants prompt medical evaluation