A nurse is reinforcing teaching with a client who has primary open-angle glaucoma and a new prescription for timolol eye drops. Which of the following statements indicates an understanding of the teaching?

Answer: D. I should check my heart rate while taking this medication.

Rationale: Timolol is a beta-blocker that can lower intraocular pressure by reducing aqueous humor production in the eye. However, it can also cause systemic effects such as bradycardia, hypotension, and bronchospasm. Therefore, clients should monitor their heart rate and report any signs of adverse reactions to the provider. Zinc supplements, eye dilation, and eye color changes are not associated with timolol use.