In the near triad, which statement accurately reflects CN involvement and functions?

• A. CN II provides parasympathetic constriction and accommodation; CN II provides afferent input; convergence is mediated by CN III.
• B. CN II controls convergence
• C. CN IV is the main contributor to the near triad
• D. CN II provides afferent input and CN III mediates parasympathetic constriction and convergence

Answer: (D)

The near triad is a coordinated response to focusing on a near object and includes three actions: pupil constriction, accommodation, and convergence. The sensory signal starts in the retina and travels via the optic nerve (cranial nerve II) as the afferent limb of the reflex. The motor commands that drive constriction of the pupil and the lens adjustment come from the oculomotor nerve (cranial nerve III) through the parasympathetic pathway to the sphincter pupillae and the ciliary muscle, and it also innervates the medial rectus muscle to produce convergence. So the correct statement is that cranial nerve II provides afferent input and cranial nerve III mediates parasympathetic constriction and convergence. Trochlear nerve is not the main contributor to the near triad, and CN II does not control convergence by itself.