Ophthalmic drug administration

Topical drops and ointments are the principal forms of ophthalmic drug administration. Drops deliver solutions, suspensions, or emulsions to the conjunctival sac, while ointments prolong contact but can temporarily blur vision. Suspensions should generally be shaken because their active ingredient is not fully dissolved. The lower eyelid is gently pulled down to form a pocket; the bottle tip must not touch the eye, eyelashes, or skin to limit contamination. A patient should close the eye gently rather than blink forcefully, and pressing the inner corner can reduce passage into the nose and systemic circulation.¹

Subconjunctival, intracameral, intravitreal, and periocular injections bypass some surface barriers and are selected when topical delivery is inadequate. Intravitreal injection places medicine directly into the vitreous and is widely used for retinal disease, including treatment with anti-vascular endothelial growth factor agents.²

The eye’s tear film, blinking, drainage, corneal epithelium, and blood–ocular barriers determine how much medicine reaches tissue. A conventional drop is often larger than the conjunctival sac can retain, so excess fluid drains through the nasolacrimal ducts or spills onto the cheek; only a small proportion may penetrate the cornea to reach intraocular structures.³

Formulation can improve residence time or tissue penetration through viscosity-enhancing polymers, mucoadhesive systems, emulsions, nanoparticles, implants, and drug-eluting inserts. These technologies may reduce dosing frequency, but they can also increase blur, irritation, manufacturing complexity, or the risk of prolonged exposure. Preservatives, especially in frequently used multidose products, may damage the ocular surface in susceptible patients; preservative-free unit-dose preparations are often considered when treatment is intensive or chronic.

Correct administration is part of treatment effectiveness and safety. Patients using more than one eye medicine should separate drops by several minutes, place ointment after liquid preparations, and follow the prescribed order when directed. Contact lenses may need to be removed because some preservatives are absorbed by lenses and can irritate the cornea. Bottles should be stored and discarded according to product instructions rather than shared between people.

Topical medicines can produce local burning, allergy, epithelial toxicity, or changes in intraocular pressure, while absorbed drugs may have systemic effects. Nasolacrimal occlusion and gentle eyelid closure can reduce systemic absorption, a particular consideration with ophthalmic beta blockers, which may affect heart rate or breathing.¹ New pain, marked redness, reduced vision, light sensitivity, or discharge after an injection requires prompt clinical assessment because infectious or inflammatory complications can threaten sight.²

Ophthalmic delivery is not limited to treating the surface of the eye. Punctal plugs can provide sustained release through the lacrimal drainage system, while subconjunctival and suprachoroidal approaches are being studied to deliver drugs to the choroid and retina without repeated intravitreal procedures. Drug-eluting contact lenses and intracameral implants likewise seek to maintain therapeutic concentrations while reducing dependence on patient technique.

Administration errors are common: patients may instill drops onto the eyelid, contaminate the tip, confuse similarly packaged medicines, or use several products too close together. Older adults and people with arthritis, tremor, poor vision, or cognitive impairment may need bottle aids, caregiver assistance, or pharmacist demonstration. The practical success of a formulation therefore depends not only on pharmacology but also on usability, adherence, sterility, and the patient’s ability to deliver the intended dose.

Ocular surface

The cornea, conjunctiva, tear film, and related tissues exposed to the external environment.

Nasolacrimal occlusion

Gentle pressure over the inner corner of the closed eyelids to reduce drainage of an eye drop into the nose.

Intravitreal injection

Injection of medicine into the vitreous body inside the eye.

Preservative-free formulation

A product without an antimicrobial preservative, commonly supplied in single-use containers.