Which of the following is not a possible side effect of a cycloplegic drug?

• A. Photophobia
• B. Blurred vision
• C. Dry mouth
• D. Increase in heart rate

Answer: (D)

Cycloplegic drugs work by blocking muscarinic receptors, which stops the eye from contracting the ciliary muscle (paralysis of accommodation) and causes pupil dilation. That combination leads to light sensitivity (photophobia) and blurred vision from loss of focus, and the anticholinergic effect also reduces saliva, producing dry mouth. These are the classic local ocular side effects you’d expect with typical eye drops.

Increase in heart rate is not a typical side effect of standard topical cycloplegics. It can occur with systemic or higher-dose forms of anticholinergic medications, but with ordinary eye drops used for cycloplegia, tachycardia isn’t a common or expected result.