Instilling an eye drop looks like the simplest task in nursing. It is also one of the most commonly performed incorrectly, and the errors are not trivial. Three things make ophthalmic administration genuinely different from other routes. First, the target is a delicate surface that the medication must reach without the dropper ever touching it — contact contaminates the bottle and can abrade the cornea. Second, the eye holds only a fraction of a drop, so technique determines dose far more than the number of drops does. Third, and least appreciated, eye drops are systemically absorbed. The conjunctival and nasal mucosa deliver drug straight into the circulation without first-pass hepatic metabolism, which is why a glaucoma drop can cause bradycardia and bronchospasm, and why a dilating drop can cause tachycardia and confusion in a frail older adult. Adherence compounds all of this. Chronic ophthalmic therapy — glaucoma above all — is asymptomatic, lifelong, and administered by the patient. Many patients cannot physically instil a drop, and a substantial proportion of those never say so. A drop that lands on the...