Anisocoria is the term for pupils of unequal size. This patient has a 5 mm pupil on the right and a 3 mm pupil on the left, so the pupils are unequal. The prefix aniso- means unequal. The ending -coria points to the pupil. Put the parts together and the word names exactly what you measured.
Some inequality is normal. The textbook calls a small difference physiologic anisocoria and treats pupils as equal when they differ by no more than 1 mm. Measure both pupils in dim light and record each size in millimeters. You can hold a millimeter rule near the eye or match the pupil to the printed circles on a near vision card. Size is only half the exam. You still check how fast each pupil constricts to a bright light and how it reacts to a near target. A large difference, a sluggish pupil, or a new droopy lid is what separates a normal finding from one the ophthalmologist needs to see. Room light changes pupil size, so measure both eyes in the same light. The iris sphincter muscle narrows the pupil in bright light. The dilator muscle widens it in dim light. If one of those muscles or its nerve is damaged, the two pupils stop matching.
Measure pupils in dim light, write both numbers, and report any inequality over 1 mm before drops go in. Never guess a size from memory, and never chart "pupils equal" without measuring. Measuring and naming pupil findings is a core part of the COA pupil assessment content area.
Incorrect Answers
- A. The ending -eikonia comes from the Greek word for image, not pupil. This term is about images, so it does not describe pupil size.
- B. The ending -cytosis points to cells, and this word is used for blood cells. It is not an eye finding at all.
- D. The ending -metropia points to refractive error, the glasses prescription. It names a difference between the two eyes' prescriptions, not their pupils.
Testing Pearls
- Aniso- means unequal, so read the ending of the word to find the body part.
- Pupils differing by 1 mm or less are usually called equal; this is physiologic anisocoria.
- Measure pupil size in dim illumination, before any dilating drops.
- Always record both pupil sizes in millimeters, not just the word "equal."
- Use a millimeter rule held near the eye, or the printed pupil circles on a near vision card. Pupil size is only part of the exam. Also check speed of constriction and the reaction to a near target.
References
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 8, Comprehensive Medical Eye Examination.
