a disease affecting the information pathways to the pupil.a disease affecting the iris, or colored area.Pathological anisocoria: This type is when the difference in pupil size comes from one of the following: 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. The difference between the pupil sizes is more or less constant, even when the light changes, and is not usually of concern. Physiological anisocoria may be temporary or permanent, depending on individual cases.Ībout 15–30% of the population experiences physiological anisocoria. It is the most common type of anisocoria, and the difference between the pupil sizes is no more than 1 millimeter. Physiological anisocoria: This is when the pupils are naturally different sizes. Share on Pinterest Physiological anisocoria is the most common type of anisocoria. Please send feedback, questions and corrections to. Questions prior to September 2016 are archived at įollow to be notified of new neuro-ophthalmology questions of the week. More than 600 additional neuro-ophthalmology questions are freely available at. University of Michigan Kellogg Eye Center

Other suspected diagnoses can wait, but anisocoria must always be evaluated unless you are convinced it is physiologic.” If you suspect third cranial nerve palsy, refer immediately for brain imaging. What to do (when a pupil is sluggishly reactive to light)? The pupil is usually irregular in shape and magnified examination shows evidence of muscle damage.” Inflammation and trauma to the iris sphincter are other causes of anisocoria.

This occurs most commonly among hospital personnel and those exposed to atropine-containing plants. If parasympatholytic (atropine-like) chemicals come in contact with the conjunctiva by accidental (or deliberate!) instillation, they will deactivate the iris sphincter muscle and cause (often very wide) pupil dilation. Ptosis is usually present but is always mild (2 mm or less).įor more information on Horner’s syndrome see Ptosis in this section. ➧Horner’s syndrome causes anisocoria in which the affected pupil is smaller, but both pupils react briskly to light. However, anisocoria is never caused by a third nerve palsy unless there are other signs of a third cranial nerve palsy-ptosis, reduced ocular movements, or ocular misalignment.Ī common cause of isolated anisocoria is a viral infection of the ciliary ganglion (Adie’s syndrome), an orbital structure that receives the parasympathetic component of the third cranial nerve. The major concern, as with ptosis, is a third cranial nerve palsy, especially one caused by an aneurysm. ➧Parasympathetic innervation failure causes a relatively dilated pupil that reacts sluggishly to direct light. “Anisocoria, or a difference in the diameter of the pupils in dim illumination, may be physiologic if the difference is less than 1 mm and both pupils react briskly and equally to light. Which of the following possibilities should be considered? Examination of the pupils reveals that the right pupil reacted briskly to light, whereas the larger left pupil was very sluggishly reactive. Question: A patient presents with anisocoria.

One pupil larger than other