In patients receiving long-term topical therapy, local toxic or hypersensitivity reactions to the active agent or preservatives may develop (Figure 7–8), especially if there is inadequate tear secretion
Preservatives in contact lens cleaning solutions may produce similar problems
Burning and soreness are exacerbated by drop instillation or contact lens insertion; occasionally, fibrosis and scarring of the conjunctiva and cornea may occur
Preservative-free topical medications, increasingly used in the treatment of glaucoma, and preservative-free contact lens solutions are available
An antibiotic instilled into the eye can sensitize the patient to that drug and cause an allergic reaction upon subsequent systemic administration
Potentially fatal anaphylaxis is known to occur in up to 0
3% of patients after intravenous fluorescein for fluorescein angiography
Anaphylaxis also has been reported after topical fluorescein
6
Systemic Effects of Ocular Drugs The systemic absorption of certain topical drugs (through the conjunctival vessels and lacrimal drainage system) must be considered when there is a systemic medical contraindication to the use of the drug
Ophthalmic solutions of the nonselective beta-blockers, eg, timolol, may worsen bradycardia, heart failure, or asthma
Phenylephrine eye drops may precipitate hypertensive crises and angina
Also to be considered are adverse interactions between sys- temically administered and ocular drugs
Using only 1 or 2 drops at a time