If one pupil is bigger than the other, this condition is called anisocoria. It means the pupils are unequal in size. This can be normal for about 20% of people (physiologic anisocoria), where the size difference is small and the pupils respond normally to light without other symptoms. However, anisocoria can also indicate various underlying conditions affecting the eye or nervous system, ranging from harmless to potentially serious.
Common Causes of Anisocoria
- Physiologic (normal) anisocoria : A harmless condition present naturally in some individuals.
- Eye disorders : Such as injuries, inflammation (iritis), glaucoma, or medications affecting the eye (like certain eye drops or substances).
- Nervous system disorders : Damage or disease affecting nerves controlling the pupil, such as Horner syndrome, third cranial nerve palsy, brain injury, stroke, tumors, or infections.
- Other causes : Exposure to chemicals, certain medications, or post-surgery effects.
When to Seek Medical Attention
- Sudden onset of unequal pupil size.
- Additional symptoms like eye pain, redness, vision loss, drooping eyelid, double vision, headache.
- If pupil size difference is large or persistent.
- Symptoms suggesting neurological issues like Horner syndrome (small pupil, drooping eyelid, lack of sweating on one side of face).
For children, unequal pupils require careful evaluation to rule out serious conditions like nerve issues or cancer (neuroblastoma). In summary, one pupil being bigger than the other can be a normal variation or a sign of underlying medical issues that may require prompt evaluation by a healthcare professional to determine the cause and need for treatment.