Final answer:
Mydriatic agents like phenylephrine cause pupil dilation during an ophthalmic exam by binding to adrenergic receptors in the iris, an effect known as mydriasis.
Step-by-step explanation:
The type of medication that causes pupils to dilate during an ophthalmic exam is known as a mydriatic agent. Phenylephrine is a common example of such a medication. It mimics the action of norepinephrine by binding to adrenergic receptors in the radial fibers of the iris smooth muscle, thus inducing dilation. This dilation is referred to as mydriasis. Phenylephrine is used in ophthalmologist's or optometrist's offices during eye exams to provide a better view of the interior structures of the eye. On the other hand, pilocarpine is a medication used to constrict the pupils and reverse mydriasis after an exam or to treat conditions like glaucoma by reducing intraocular pressure.