What should be done after instilling eyedrops to ensure their effectiveness?

Blocking the nasolacrimal duct with a finger after instilling eyedrops is an effective technique to enhance the medication's absorption and therapeutic effect. This method helps prevent the drops from draining into the nasal cavity, which can lead to systemic absorption and decrease the ocular concentration of the medication. By blocking the duct, the medication remains in contact with the ocular surface longer, thereby increasing its potency and effectiveness in treating the condition for which it was prescribed.

In contrast, encouraging the patient to blink can inadvertently help distribute the medication across the surface of the eye, but it doesn't effectively prevent drainage or enhance absorption as well as blocking the duct does. Instructing the patient to close their eyes tightly could lead to discomfort and does not promote the desired medicinal effect. Having the patient swallow is irrelevant in the context of administering eyedrops, since it does not impact the effectiveness of the medication.