One variable and subjective decision when managing animal eye diseases is how often to apply eye drops. In this post, we shed some light on some of the factors that influence the frequency of treatment. 

1. Antibiotics

Recommend: 3 times daily or more

The most common indication for topical ophthalmic antibiotic therapy is corneal ulcers. Non-infected corneal ulcers may be appropriately treated with broad-spectrum topical antibiotics 2-3 times daily. However, infected corneal ulcers often necessitate more aggressive antibiotic therapy, with the frequency approaching hourly in very severe cases. 

2. Atropine

Recommend: 2 times daily or less

Atropine sulfate 1% is a commonly prescribed mydriatic (pupil dilator) that has several beneficial effects including reducing the risk of posterior synechia (iris to lens adhesions), paralyzing the ciliary muscles (relieving discomfort), and stabilizing the blood-ocular barrier (reducing inflammation). However, this medication may cause well-recognized adverse effects including hypersalivation, tachycardia, and elevation in intraocular pressure. Because the effect of the medication is prolonged, infrequent treatment is often sufficient.   

3. Timolol

Recommend: 2-3 times daily or less

Timolol is a topical ophthalmic beta-blocker commonly used for glaucoma.  It may adversely impact cardiopulmonary function with bradycardia noted in some individuals receiving the medication.  Caution must be exercised when prescribing this medication in small (low body weight) animals and those with pre-existing heart or lung diseae.   

4. Latanoprost

Recommend: 1-3 times daily or less

Latanoprost is a prostaglandin analogue often used for primary glaucoma in dogs.  While systemic side effects of the medication are rare, ocular side effects such as miosis (pupil constriction) are drastic in dogs and cats. In some secondary glaucomas like those due to uveitis and anterior lens luxation, the extreme miosis may actually exacerbate the intraocular pressure elevation and, for this reason, the medications should not be overused. 

5. Preservatives

The vast majority of commercially available medications contain preservatives. Preservatives prolong the shelf-life of products, but may also improve drug absorption by increased permeability of the corneal epithelium. However, when over-exposed to preservatives, corneal epithelial fragility may increase and predispose to the development or persistence of corneal ulcers. This scenario, although rare, may be recognized in patients receiving chronic and/or frequent topical ophthalmic medications. 

In summary, the frequency of topical ophthalmic medications application is often both key to success and key to the failure of treatment. Veterinarians and pet owners should be confident in the prescribed medication regimen or contact a veterinary ophthalmologist for guidance.