Adie’s tonic pupil is a condition where one pupil becomes larger and reacts slowly to light but better to near focus.
Underlying mechanism
It is usually due to damage to the parasympathetic nerve supply to the iris. The cause is often unknown but may follow viral infections or inflammation.
- Common in young to middle-aged adults, more often women
- Typically affects one eye, though the other may be involved later
- Pupil constricts slowly when focusing on near objects
- Light reaction is weak or absent
Associated features and outlook
Adie’s pupil is usually benign but can cause glare and difficulty focusing. Some people also develop reduced reflexes in the legs.
- May be part of Adie’s syndrome with absent ankle reflexes
- Reading glasses or dilute pilocarpine drops can improve near vision
- Condition tends to be stable or slowly progressive
- Important to distinguish from serious causes of anisocoria
