Certified Ophthalmic Medical Technologist (COMT) Practice Exam

When the dilator muscle contracts, what effect does it have on the pupil?

1. The pupil constricts

2. The pupil dilates

3. The pupil becomes oval

4. The pupil remains fixed

The correct answer is: The pupil dilates

When the dilator muscle of the iris contracts, it causes the pupil to enlarge, which is known as dilation. This muscle is part of the sympathetic nervous system and responds to low light conditions or heightened emotional states. The contraction of the dilator muscle pulls the edges of the iris outward, thereby increasing the size of the pupil. Dilation allows more light to enter the eye, thereby enhancing vision in dim environments. Understanding the role of the dilator muscle clarifies why options suggesting constriction or a fixed state of the pupil would not be accurate. The constrictor muscle, for instance, would be responsible for pupil constriction, while a fixed pupil refers to a lack of response to stimuli, which is not associated with the activity of the dilator muscle. Therefore, selecting the correct answer reflects an understanding of the anatomy and physiology of the eye, specifically regarding how the muscles of the iris regulate pupil size.