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Why is one eye suddenly smaller than the other?

Medically reviewed by Kristianne Hannemann, PharmD. Last updated on Sep 16, 2024.

Official answer

by Drugs.com

If one eye suddenly appears smaller than the other, it could be due to a condition called ptosis. Ptosis occurs when the upper eyelid droops lower than normal, giving the affected eye a smaller appearance. This can develop suddenly and may affect vision if the drooping eyelid covers part of the pupil.

There are several potential causes of sudden ptosis, including:

  • Muscle weakness: Conditions like myasthenia gravis can affect the muscles that control the eyelid, leading to drooping. This can happen after birth or later in life.
  • Nerve damage: Nerve issues, such as those caused by a stroke or a brain tumor, can affect the eyelid’s muscles, causing one eye to droop.
  • Local eye problems: Infections or trauma to the eye or surrounding tissues can also lead to a drooping eyelid.
  • Aging: In some cases, ptosis can develop with age as the muscles that lift the eyelid weaken over time.
  • Medications: Certain medications, such as botulinum treatment (e.g., Botox) can cause ptosis as a side effect.

If you notice this symptom, especially if it develops suddenly, it’s important to see a doctor for evaluation. Sudden ptosis can be a sign of an underlying medical issue that needs to be addressed. Treatment of ptosis depends on the cause, but may include surgery or medications.

References

Shahzad, B., et. al. Updated August 2023. Ptosis. In: StatPearls [Internet]. Accessed September 16, 2024 at https://www.ncbi.nlm.nih.gov/books/NBK546705/

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