Why is One Pupil Larger than The Other?

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Why is One Pupil Larger than The Other?

The pupil of one eye is larger than the other and this condition is observed in a disorder named as Anisocoria. The quantity of light that enters the eye is controlled by the pupil. The pupil narrows down in bright light and dilates in low light. The muscles in the Iris region show some problem in getting dilated and hence lead to Anisocoria. The difference in sizes of the pupils here ranges from small to very large. It is observed that there might be some neurological problems in Anisocoria. This problem if existed for a short period will not be an issue. The problem when persists will create an issue.

The reduction in size of the pupil is also seen in Horner’s syndrome. This condition will result due to the injury of oculosympathetic nerve. The opening of eyelid happens due to this nerve. The pupil will be very small and will not expand when it faces the dark surroundings. The pupil will not respond to the changes in the light intensity due to the damage of sympathetic nerves that connect the carotid artery and brain. Normally sympathetic nerves maintain the functions of sweating, blood pressure and heart rate.

The enlargement of pupil size might be caused due to the injury to the oculomotor nerve. This nerve maintains the movement of the eye. This nerve also controls the opening of eyelid by regulating the muscle that is involved in this function. The constriction of Iris is also done by this muscle and in turn by the oculomotor nerve. When there is any problem with this third cranial nerve, the patient will have double vision and the pupil enlarges. These difficulties with the pupil will result in aneurysm.

Another disorder that causes the change in size of the two pupils is Adie’s pupil. This is caused due to the injury to the nerve fibers that control the muscles of the eye. The muscles of the eye will in turn control the movement of the eye. The patients with this disorder cannot concentrate their both pupils on nearer objects for long time.

Author: Hari M

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