Describe the near triad and the nerves involved.

• A. Accommodation, convergence, and pupil constriction; mediated by parasympathetic output from Edinger-Westphal via CN III to the ciliary ganglion.
• B. Accommodation and convergence only, with no pupil response.
• C. Pupil constriction and eyelid retraction; mediated by CN III.
• D. Lateral gaze and eyelid elevation; mediated by CN VI.

Answer: (A)

When focusing on a nearby object, the eyes perform a coordinated set of actions: accommodation (the lens becomes more rounded to increase refractive power), convergence (the eyes turn inward so both foveas aim at the object), and pupil constriction (smaller pupil to improve depth of field and reduce aberrations). This trio is driven mainly by parasympathetic signals that originate in the Edinger-Westphal nucleus and ride along the oculomotor nerve to the ciliary ganglion. From the ciliary ganglion, postganglionic fibers travel via short ciliary nerves to the ciliary muscle (driving accommodation) and to the sphincter pupillae (driving pupil constriction). The convergence component is mediated by the same oculomotor pathways activating the medial rectus muscles. It’s separate from the sympathetic system, which controls pupil dilation and is not part of the near triad.