Oral treatment options abound for dry eye

Key Points

One's eyes can be affected by systemic medications and nutrition habits, both of which contribute to dry eye. Oral treatment options should be considered for systemic causes of dry eye and certain other cases, whereas topical treatment with artificial tears is the best option for external causes.

Systemic medications

Systemic medications, particularly antihistamines, often play a significant role in the exacerbation of dry eye. Five classes of drugs are known to have ocular drying effects: antihistamines, antihypertensives, antiemetics, tricyclic antidepressants, and diuretics.

Antihypertensives (e.g., beta blockers), antiemetics (through their mechanism of blocking serotonin receptors), and tricyclic antidepressants are thought to cause ocular drying as well through antimuscarinic activity.^3,4 The mechanism by which diuretics cause ocular dryness is not completely understood, but reduction in tear production is a documented side effect and may be related to dehydration secondary to diuresis.⁵ Capturing a comprehensive medical history can provide valuable information on the potential relationship of a patient's medications to his or her dry eye.

Nutrition

Just as the eyes can be affected by systemic medications, they also can be influenced by systemic biologic processes. Five known nutritional factors are related to dry eye: hydration, omega-3 fatty acids, antioxidants, carotenoids, and vitamin intake. Recommending that patients drink plenty of water is a good first step in treatment.⁶ Flaxseed oil, evening primrose oil, and fish oil supplements, all high in omega-3 fatty acids, offer potential benefits for dry eye.

The Brigham and Women's Hospital-based Women's Health Study demonstrated a relationship between higher dietary intake of omega-3 fatty acids and decreased incidence of dry eye in women, whereas higher ratios of omega-6 to omega-3 fatty acids were associated with an increased risk of dry eye.⁷ For example, the metabolites of one of these omega-6 fatty acids, arachidonic acid, are known contributors to ocular inflammation, so it is important patients' consumption of omega-3 fatty acids is sufficient.⁸

With research demonstrating the potential ophthalmic impact of consumption of foods high in carotenoids and intake of vitamins A, C, and E, clinicians can prescribe a nutritional supplement combining these nutrients.⁹ One mixture of vitamins, minerals, antioxidants, phytonutrients, and omega-3 fatty acids was designed specifically for dry eye, and clinical study revealed the supplement to be significantly more effective in alleviating ocular discomfort versus placebo when subjects were exposed to the Controlled Adverse Environment.¹⁰

Additional properties

Beyond nutritional influences, other systemic agents can influence dry eye. If a receptor antagonist can cause dry eye, why not use a receptor agonist to treat insufficiencies in tear production? One muscarinic receptor agonist, pilocarpine, is used as treatment for dry mouth associated with Sjögren's syndrome (SS) and has demonstrated efficacy in improving signs and symptoms of dry eye in patients with SS.¹¹ Systemic immunomodulatory therapy has also demonstrated significant improvement in tear production and keratoconjunctivitis due to severe cases of dry eye secondary to autoimmune diseases.¹²

For dry eye patients exhibiting meibomian gland dysfunction, a systemic tetracycline can be prescribed. These agents possess anti-inflammatory properties in addition to their antimicrobial ability and have become a useful option for management of chronic ocular surface inflammatory diseases. The American Academy of Ophthalmology recommends that the clinician prescribe oral tetracycline or doxycycline for a reduction in side effects and less frequent dosing scheme, on a tapered dose.¹³