Certified Ophthalmic Assistant Practice Exam

The site where half the nerve fibers from each eye cross over to the opposite side is called the optic

1. iris

2. canthi

3. stoma

4. chiasm

The correct answer is: chiasm

The optic chiasm is the anatomical structure where half of the nerve fibers from each eye cross to the opposite side of the brain. This crossing allows visual information from each eye to be processed by both hemispheres of the brain, which is essential for depth perception and a unified visual field. The optic chiasm is located at the base of the brain, just in front of the pituitary gland. In contrast, the other terms provided do not refer to this specific structure. The iris is the colored part of the eye that helps control the amount of light entering the eye. The canthi refer to the corners of the eye where the upper and lower eyelids meet, and the stoma is not related to eye anatomy but rather refers to openings or a mouth-like structure in biology. Thus, recognizing the specific function and location of the optic chiasm is crucial for understanding visual processing.