If an ophthalmologist wants to dilate the pupils for an eye examination, which class of drugs would be most effective?

To effectively dilate the pupils for an eye examination, an ophthalmologist would utilize muscarinic receptor inhibitors, also known as anticholinergics. These drugs work by blocking the action of acetylcholine on muscarinic receptors found in the iris sphincter muscle. When these receptors are inhibited, they prevent constriction of the pupil, leading to dilation (mydriasis). This is particularly useful during eye examinations as it allows for a better view of the internal structures of the eye.

In the context of the other options, muscarinic receptor activators would cause pupil constriction rather than dilation, and pilocarpine, which is a muscarinic agonist, also results in miosis (pupil constriction) rather than mydriasis. Neostigmine is a cholinesterase inhibitor that increases the levels of acetylcholine at synapses, leading to enhanced activation of both nicotinic and muscarinic receptors; however, this too would promote pupil constriction instead of dilation. Therefore, the most effective class of drugs for inducing pupil dilation in this scenario is indeed muscarinic receptor inhibitors.