Tadpole pupil
The pupils are normally equal, round and equally reactive to light and near. In some conditions the pupils become abnormally shaped or exhibit unusual behavior.(Table) A tadpole pupil is one that intermittently and briefly becomes elongated and comma-shaped because of spasm involving one sector of the pupillodilator.(1-3) It is a benign condition.
Aggarwal and Hildebrand published an example of a tadpole pupil online in JAMA Neurology February 20, 2017.(4) The patient was a 2-year-old girl who presented with episodes in which the right pupil became oval. The tadpole pupil would begin to improve after 10 minutes and completely resolved after 40 minutes. She was otherwise well and had no other neurological symptoms. MRI excluded any pathology.
Table. Some of the unusual pupillary shapes, reactions and behaviors that occasionally occur.
| Pupil | Characteristic |
|---|---|
| Paradoxical pupils | Constrict in darkness; seen in congenital retinal and optic nerve disorders |
| Springing pupil | Intermittent, sometimes alternating, dilation of one pupil lasting minutes to hours seen in young, healthy women, often followed by headache. |
| Tadpole pupil | A benign condition in which a pupil intermittently and briefly becomes comma-shaped because of spasm involving one sector of the pupillodilator |
| Periodic unilateral mydriasis | May occur in migraine and as an ictal phenomenon |
| Scalloped pupils | Suggestive of familial amyloidosis |
| Oval pupils | Usually portend major intracranial pathology; may be a transient phase in evolving injury to the third nerve nuclear complex |
| Corectopia iridis (ectopia pupillae, Wilson’s sign) | Spontaneous, cyclic displacement of the pupil from the center of the iris; it is usually seen in severe midbrain disease |
