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The colored part of the eye is called the iris. It is a circular muscle, similar in shape to a donut. The empty hole in the middle, which allows light to enter the eye, is called the pupil. When in a bright room or outdoors the pupil usually gets smaller or constricts ; conversely when in a dark room the pupil usually gets bigger or dilates to allow more light to enter the eye [See figure 1]. Normally the size of the pupil is the same in each eye, with both eyes dilating or constricting together.
The term anisocoria refers to pupils that are different sizes at the same time. The presence of anisocoria can be normal physiologicor it can be a of an underlying medical condition. The amount of anisocoria can vary from day-to-day and can even switch eyes. Anisocoria that is NOT associated with or due to an underlying medical condition is called physiologic anisocoria.
Typically, with physiologic anisocoria, the difference in pupil size between the two eyes does not exceed one millimeter.
In physiologic anisocoria, the difference in pupil size does not change under bright or dim light. Certain characteristics, such as when the anisocoria was first noted, whether it is more noticeable in bright or dim light, and whether there was an event that occurred in the past that could have caused it, will help determine the underlying cause.
A complete eye examination is performed by a pediatric ophthalmologist or neuro-ophthalmologist to evaluate vision, eyelid position, how the eyes move, and the health of the front and back portions of the eyes among other things. The doctor will evaluate the size of the pupils and how they react to bright and dim light. Based on the evaluation, the doctor may wish to perform additional tests with eyedrops or perform laboratory or radiologic testing. One of the most important parts in the evaluation of anisocoria is determining which pupil is abnormal. If the difference in size between the pupils increases in the dark, then the smaller miotic pupil may not be dilating well and could be the abnormal one.
On the other hand, if the difference in pupil size increases in bright light, then the larger mydriatic pupil may be the abnormal one because it is not getting small or constricting normally. After trauma to the eye, the colored part of the eye i. This is a condition most common in young adult females, which usually begins in one eye. The pupil is slow to react to light.
Many people with this condition will also have diminished deep tendon reflexes and they can have trouble focusing at near. The condition is usually not associated with any serious conditions. Some eyedrops, nasal sprays, or other medications can have a dilating effect on the pupil. There have been cases of prescription anti-perspirant wipes that have accidentally gotten in the eye and caused temporary pupil dilation. Finally, an abnormality of the third cranial nerve a nerve that comes from the brain to the eye and controls eyelid position, eye movement, and pupil size can cause an abnormality of the pupil.
In this condition, there is often droopiness otherwise known as ptosis of the upper eyelid on the same side as the larger dilated pupil. In addition, the eye may not move normally, and an older child might complain of double vision. A third cranial nerve palsy can be a of a serious condition, and the doctor may want to order immediate testing, including imaging studies of the brain.
Inflammation within the eye, whether from trauma or another cause, can result in a small miotic pupil. The difference in pupil size between the two eyes is more noticeable under dim light. The child may have mild droopiness ptosis of the upper eyelid [See figure 2]. Sometimes the lower eyelid may be slightly higher than normal known as inverse ptosis. When the upper eyelid is slightly lower than normal and the lower eyelid is slightly higher than normal, the eye may appear smaller.
Sometimes, the pressure in the eye is lower in the affected eye and sometimes there is decreased sweating or flushing of the skin on the face on the affected side anhydrosis. Acquired cases can be due to neck trauma, neck surgery, or an abnormality in the chest, neck, or brain.
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Skip auxiliary Press Enter. Skip main Press Enter. Toggle. Anisocoria and Horner's Syndrome. Print Version What is the pupil? Is it normal to have pupils of different sizes? When is anisocoria normal? How does the doctor determine whether anisocoria is due to an underlying medical problem?
What are some causes of an abnormally large dilated or mydriatic pupil? What are some causes of an abnormally small miotic pupil? Last Updated By: Christina Scott Related Links HL Admin. Anisocoria - Definition. Search by Eye Terms Eye Conditions. Translate :. Site by eConverse Media. Powered by Higher Logic.Horner single women
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