Situation: A 72-year-old man with type 2 diabetes mellitus and hypertension is scheduled for phacoemulsification with intraocular lens implantation in the right eye under topical anesthesia. Over the past 2 years he has noticed gradually blurred vision and glare when driving at night. After surgery, antibiotic eye drops, corticosteroid eye drops and an antibiotic eye ointment are all due at 22:00. Which plan is correct?

When several eye medications are due together, the nurse waits at least 5 minutes between different drops so the second does not wash out the first, and gives drops before ointment, because ointment leaves a film that keeps drops from reaching the eye.

When several ophthalmic medications are ordered at the same time, the sequence and spacing determine how much of each drug actually reaches the ocular surface. The correct plan is to instill the two different eye drops 5 minutes apart, and to apply the ointment last.

The reason is straightforward. A drop that is instilled immediately after another drop will dilute and wash away the first medication before it can be absorbed. Waiting at least 5 minutes allows the first drop to remain in contact with the cornea and conjunctiva long enough for adequate absorption. Different eye drops should be separated by at least 5 minutes so the second drop does not rinse out the first.

Ointment must always be given after drops. Ointment forms a hydrophobic, occlusive film over the ocular surface. If ointment is applied first, that film creates a physical barrier that prevents subsequent drops from reaching the cornea and conjunctiva. Drops are given before ointment because an ointment film blocks or delays penetration of later drops. When the ointment is placed last, it also helps retain the previously instilled drops on the eye longer, which can enhance contact time.

The scenario involves a patient who has undergone phacoemulsification with intraocular lens implantation. Postoperative topical regimens after cataract surgery typically include an antibiotic to reduce the risk of postoperative endophthalmitis and a corticosteroid to control inflammation. The French Agency for the Safety of Health Products recommends topical antibiotic prophylaxis for any ocular surgery until the incisions are sealed, reflecting the importance of delivering the antibiotic reliably to the surgical site ^[2]. If the antibiotic drop is washed out by immediate instillation of the corticosteroid drop, or if it is blocked by an ointment applied first, the intended prophylactic coverage is compromised.

This patient also has type 2 diabetes mellitus. Diabetic patients undergoing cataract surgery are at increased risk for postoperative macular oedema, and topical anti-inflammatory agents are part of the preventive strategy in this population ^[3]. Reliable delivery of the corticosteroid drop is therefore clinically relevant. Giving the corticosteroid drop after a proper interval and before the ointment helps ensure that the anti-inflammatory drug reaches the ocular surface in an effective concentration.

Order	Action	Rationale
First	Instill antibiotic eye drop	Delivers prophylactic antimicrobial coverage to the surgical eye
Wait 5 minutes	Do not instill anything	Allows absorption and prevents washout by the next drop
Second	Instill corticosteroid eye drop	Controls postoperative inflammation; reduces risk of macular oedema in diabetic patients
Wait 5 minutes	Do not instill anything	Allows the corticosteroid to remain in contact with the eye
Last	Apply antibiotic eye ointment	Provides prolonged contact time and does not block absorption of the drops given before it

Watch out! The ointment is never given first. An ointment base is greasy and forms a film that prevents water-based drops from reaching the ocular surface. If a patient needs both drops and ointment at the same scheduled time, the drops always precede the ointment.

Key point! The interval of 5 minutes applies between different drops. If only one drop and one ointment are ordered, the drop is given first and the ointment can follow after a brief pause, but the minimum interval between different drops remains the critical rule when multiple drops are due together.

In this scenario, giving both drops back-to-back and then applying the ointment 5 minutes later would cause the second drop to wash out the first. Giving the ointment first would block both drops. The only plan that preserves the therapeutic effect of each medication is to separate the two drops by 5 minutes and place the ointment last.