The purpose of eye exam for anisocoria is to find out whether the difference in pupil size is simply a non-harmful characteristic of your eyes or if it is the symptom of a more serious eye problem.
Your ophthalmologist will examine your pupils in both a lighted room and a dark room to see how they respond to light. This allows your ophthalmologist to determine which of the pupils is reacting abnormally. If the difference in pupil sizes is greater in light, the larger pupil is abnormal. If the difference in size is greater in the dark, the smaller pupil is abnormal.
Your ophthalmologist will also conduct a slit-lamp exam. With this special microscope, the doctor is able to examine your eye in small, detailed sections, making it easier to spot abnormalities.
Many cases of anisocoria are physiologic anisocoria, which are simply the result of normal differences in people’s eyes and are not related to a health problem.
If you are having other symptoms along with anisocoria, your ophthalmologist will conduct other tests that are appropriate to the symptoms. Two eye disorders for which anisocoria is a common symptom are third nerve cranial nerve palsy and Horner’s syndrome. Both are nervous system disorders that can occur when nerves that travel to the eye are damaged by a stroke, tumor or trauma. Other causes include:
- Viral infection
- Damage as a result of surgery
- Adie’s tonic pupil, a neurological condition in which one eye does not dilate or respond to light as well as the other
Image courtesy of Steven A. Newman, MD.