What are the two primary ophthalmic effects of atropine?

Atropine is an anticholinergic agent that primarily affects the parasympathetic nervous system. In ophthalmology, it is particularly noted for causing mydriasis, which is the dilation of the pupil, and cycloplegia, which is paralysis of the ciliary muscle leading to an inability to focus on near objects.

Mydriasis occurs due to the inhibition of the iris sphincter muscle, which is supplied by the parasympathetic fibers. When these fibers are blocked by atropine, the constrictor muscle is unable to contract, resulting in pupil dilation. Cycloplegia results from the paralysis of the ciliary muscle, preventing accommodation, which can be particularly useful in procedures requiring a stable view of the retina or lens.

The other effects mentioned in the options do not align as closely with the primary actions of atropine in ophthalmology. For instance, while it can sometimes lead to photophobia due to light sensitivity from dilated pupils, this symptom is not a primary effect of the drug itself. Similarly, increased intraocular pressure is not a direct consequence of atropine use, and dry eyes or increased tear production are not associated with its pharmacological action. Thus, mydriasis and cyclopleg