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Pupils are holes in the iris of the eye. They allow the light to enter the eye and reach the retina. Normally pupils dilate if there is not enough light and in bright light they shrink. This occurs simultaneously and both pupils are involved in dilatation or constriction. They are commonly even in size and in some medical conditions one can be dilated or shrink while other stays normal. If the pupils are uneven in size this medical condition is called anisocoria.

Symptoms of Uneven Pupils

Anisocoria may be mild and sometimes the difference in size between the pupils can be drastic. The only sign is uneven size of the pupils. The cause is related to the muscles which are in charge with dilatation and shrinkage of the pupils. These muscles are innervated by autonomous nervous system. Dilatation and shrinkage of the pupils is unconscious and cannot be controlled.

Some people who are suffering from uneven pupils may experience fear or pain of light which is called photophobia. The eyes may be also exposed to increased strain. This leads to pain. Additional symptoms may include headaches and migraines.

Causes of Uneven Pupils

Uneven size of the pupils may be hereditary or acquired. There are numerous causes of this medical condition.

Certain eye drops such as those used in allergies may cause dilatation of pupils. Luckily eye drops only cause transitory problems and there is no reason for the patient to worry about unevenness of the pupils.

Certain plants may induce anisocoria if they come in contact with the eyes. These plants cause irritation of the eyes and rubbing of the eyes can only make the situation worse. Some of them are Angel Trumpet, Deadly Nightshade, Yellow Jessamine flower, and so on.

Anisocoria commonly occurs in severe head trauma. It points to serious damage of the brain and its structures and requires prompt medical help and treatment.

In Horner's syndrome typical triad occurs. It includes ptosis, miosis and enophtalmus. One pupil is smaller than the other. Horner's syndrome may occur as a consequence of damaged oculosympathetic nerve, sympathetic nerves that run down the carotid artery etc.

In case that the oculomotor nerve is damaged the patient will definitely have uneven pupils. Additional symptoms include double vision and dropping of the eyelids.

In Adie's Pupil the actual cause of anisocoria cannot be identified. Some believe that viral or bacterial infection is responsible for unevenness of the pupils. Still, in patients who are suffering from this condition pupils sometimes spontaneously restore their normal size.

Additional causes of anisocoria include meningitis, encephalitis, brain tumors and sometimes chest tumors. Apart from that even abuse of some drugs such as cocaine or marijuana may cause anisocoria.

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