Russel Lazarus, November 11, Different sized pupils could indicate a serious health issue requiring urgent medical care. Occasionally, the two pupils can appear unequal in size. What causes unequal pupils? There are four main types and causes of anisocoria: 1. Simple anisocoria Also called essential anisocoria and physiologic anisocoria, this is the most common type of anisocoria, that has been shown to affect 20 percent of people.
The precise cause of this type of anisocoria has yet to be discovered. Find an eye doctor near you Search near me. Back to: What Is Degenerative Myopia? Find an Eye Doctor Search near me. Aniridia a complete or partial absence of the iris of one eye. Ectopic pupil an inherited condition that causes displacement of the pupil and dislocation of the lens. Certain glaucoma eye drop medications also can cause anisocoria, especially if they are used to treat glaucoma in just one eye.
Examples of glaucoma medications that can cause anisocoria include:. If you or someone else notices that you have unequal pupil sizes, see your eye doctor immediately — especially if you have any of the following:. If the anisocoria is minor and your pupils react normally to tests your eye doctor performs, there may be nothing to worry about. But you should have your unequal pupils evaluated by an eye care professional or neurologist before you assume all is well.
If you have anisocoria and one pupil is bigger than the other, ask your eye doctor about photochromic lenses. These eyeglass lenses will darken automatically in sunlight to reduce any light sensitivity photophobia you may be experiencing. Photochromic lenses also will protect your eyes from harmful UV rays and high-energy blue light — especially the eye with the larger pupil if it doesn't react normally to light.
The prevalence of simple anisocoria. American Journal of Ophthalmology. July American Academy of Ophthalmology. The difference between the pupil sizes is more or less constant, even when the light changes, and is not usually of concern. Mechanical anisocoria : This type of anisocoria is the result of physical damage to the eye, such as an injury or a condition that causes inflammation to the eye. Pathological anisocoria : This type is when the difference in pupil size comes from one of the following:.
Anisocoria may not have an underlying cause. This is not harmful and does not require treatment. Causes of TNP include a brain hemorrhage, trauma, or aneurysm. Anyone experiencing symptoms after a head injury must see a doctor. Other causes of TNP in children include migraine and severe infections, such as meningitis. However, some cases of TNP in children are congenital, meaning they occur from birth.
TNP can be due to pressure on the third nerve from an artery aneurysm. An aneurysm causes pain and is a life-threatening condition that needs immediate attention.
They will also have all or some of the following symptoms:. Tonic pupil is where one pupil will appear abnormally large in light, taking a long time to constrict. It is not a life-threatening condition. 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 physiologic , or it can be a sign 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.
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