Anisocoria (Unequal Pupil)

Anisocoria refers to a condition in which a person’s pupils are unequal in size. While slight pupil size differences can be normal and harmless (physiologic anisocoria), more noticeable disparities may signal an underlying eye or neurological issue. It can be present from birth or develop later in life. Identifying whether anisocoria is benign or linked to other health concerns often requires a professional eye examination.

• Physiological anisocoria – harmless, natural pupil size variation

• Eye trauma – injury affecting iris muscles or nerves

• Medications – eye drops like pilocarpine or atropine

• Nerve damage – affecting cranial nerves (e.g., Horner’s syndrome, third nerve palsy)

• Brain conditions – stroke, tumor, or aneurysm causing nerve compression

• Infections – meningitis or encephalitis impacting eye nerves

• Glaucoma – acute angle-closure type may dilate the pupil

• Unequal pupil sizes – one pupil larger or smaller than the other

• Blurred or double vision

• Eye pain or discomfort (in some cases)

• Sensitivity to light (photophobia)

• Drooping eyelid (ptosis) on the affected side

• Headache or dizziness, depending on the cause

• Difficulty focusing or eye fatigue

• May be accompanied by other neurological symptoms like facial weakness or confusion

Treatment for anisocoria depends on its cause. If it’s physiologic and harmless, no treatment is necessary. For anisocoria caused by infections, trauma, or neurological issues, managing the underlying condition is key. Your eye doctor may recommend imaging tests or refer you to a neurologist if a more serious cause is suspected. Early diagnosis and intervention can prevent potential complications and preserve vision.

Seek medical attention if anisocoria appears suddenly, worsens over time, or is accompanied by symptoms such as double vision, eye pain, severe headache, or drooping eyelid. These signs may indicate a serious condition, such as Horner’s syndrome, brain injury, or a neurological disorder. An eye specialist can determine if the anisocoria is benign or needs urgent care through proper diagnostic evaluation.