Which of the following is NOT a side effect of eye drops or medications?

Improved visual acuity is correctly identified as not a side effect of eye drops or medications. While certain medications or eye drops can enhance visual clarity or treat specific eye conditions, the term "improved visual acuity" refers to a positive therapeutic outcome rather than a side effect. Side effects are typically unintended responses to a medication that occur in addition to the desired therapeutic effect. In contrast, options like blurring, headache, and allergic reactions are well-documented side effects associated with various eye medications. These adverse effects can arise due to the formulation of the eye drops, individual sensitivity to the medication, or other factors, making them significant concerns for medical examiners when evaluating a patient's fitness for duty. By understanding these distinctions, medical examiners can better assess the impact of prescribed medications on a driver’s ability to operate a vehicle safely.