The method of instilling the drops is important. If it is not done properly, the drops have almost as much chance of landing on the cheek as in the eye.
It is important that patients wash their hands and remove any contact lenses before using the drops. Many eye drops contain the drug in suspension rather than in solution. These drops should always be shaken before use.
The cap should be removed from the bottle but never put down on the table in such a way that it may become contaminated. It should either be put on its side or held carefully in the other hand.
During instillation it is very important that patients do not touch their eye with the tip of the bottle. This could both abrade the cornea and contaminate the remaining drops.
In the traditional method of instilling drops (see Fig. 1) the bottle is held upside down in one hand between the thumb and index finger and with the other hand the lower eyelid is gently pulled down to form a pouch. The head is tilted back, the patient looks up and, placing the tip of the bottle close to their lower eyelid, gently squeezes the bottle to release one drop into the pouch formed between the eye and lid.
An alternative technique (see Fig. 2) is for the patient to hold the bottle between the thumb and index finger of their dominant hand then rest their little finger below the lower lid and use it to pull the lid out and create a pocket. Then, tilting their head back, they look up and squeeze the bottle. It is almost impossible to miss as the tip of the bottle is within two or three centimetres of the eye.
After entering the eye the drop will pass through the nasolacrimal duct into the nasopharynx. In some cases the amount of systemic absorption can be significant, especially with the beta blocker eye drops used for glaucoma. After the drop is instilled the patient should therefore close their eyes and place their index fingers against the inner corner of the eyes, pressing against the nose for one or two minutes. This punctal pressure will reduce the amount of drug that reaches the nasopharynx and thus reduce any systemic absorption.
If the patient is instilling more than one medication they should wait at least three minutes before putting in the next medication. Generally, they should wait at least 15 minutes before inserting contact lenses if they are worn.