Literature
Clinical Pearls & Morning Reports
Published June 6, 2018
What are some of the causes of dry eye?
Dry eye disease is an umbrella term that covers a host of symptoms and signs associated with compromised ocular lubrication — that is, reduced quality or quantity of tears on the ocular surface. The diagnosis of dry eye is complicated by an inconsistent correlation between reported symptoms and observed signs. This discrepancy can be largely explained by the lack of consistent results of commonly used clinical tests, the natural variability of the disease process, the subjective nature of symptoms, and individual variations in pain thresholds and cognitive responses to questions about ocular sensation. Read the latest NEJM Review Article here.
Clinical Pearls
Q: What are the components of the tear film that coats the eye?
A: The tear film that coats the eye consists primarily of aqueous, lipid, and mucin components. The lacrimal glands produce the aqueous portion, which is enriched with a complex mixture of electrolytes, enzymes, antibodies, vitamins, antimicrobial proteins, and other substances. The lipids are produced by the meibomian glands, which are modified sebaceous glands along the eyelid margin. Mucins (i.e., gelatinous glycoproteins) are produced by conjunctival goblet cells.
Q: What symptoms are associated with dry eye?
A: A frequent component of dry eye is ocular pain, which is often accompanied by light sensitivity, foreign-body (debris) sensation, dryness, and irritation. Patients often report pain evoked by exposure to wind, light, and temperature extremes. Corneal neuropathic pain can be severe and can be characterized as a burning or stinging sensation, sharp pain, or a dull ache. These perceptions most likely result from dysfunctional nerves in the richly innervated cornea. Visual symptoms, notably fluctuating or blurry vision, can be another consequence of dry eye.
Morning Report Questions
Q: What are some of the causes of dry eye?
A: Dry eye has many causes, which often overlap and interact. Autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus, can cause dry eye. Furthermore, treatments for these diseases, including methotrexate and cyclophosphamide, can also cause or exacerbate dry eye. Sjögren’s syndrome is characterized by dry eye and dry mouth. Disorders such as conjunctival chalasis and eyelid laxity (i.e., the floppy eyelid syndrome), can lead to symptoms of dry eye. Conditions that affect muscular control of the face, such as stroke, injury, or Bell’s palsy, can impair eyelid closure, resulting in lagophthalmos and leading to an extreme form of evaporative dry eye called exposure keratitis. Similarly, any condition (e.g., Parkinson’s disease) or situation (e.g., prolonged screen viewing [on a computer, cell-phone, or television, for example]) that reduces the blink rate can increase the risk of dry eye by promoting tear evaporation. Obstructive meibomian gland dysfunction alters the lipid constitution of the tears and is the most common cause of evaporative dry eye. Dry eye affects about half of patients with chronic graft-versus-host disease. Many systemic drugs have been reported to trigger dry eye.
Q: Have any new medications for dry eye been approved by the Food and Drug Administration in recent years?
A: In July 2016, the Food and Drug Administration (FDA) approved 0.5% lifitegrast ophthalmic solution (Xiidra) for treating signs and symptoms of dry eye disease. Applied topically as one drop twice daily, this medication is the first in a new class of drugs, called lymphocyte function–associated antigen 1 (LFA-1) antagonists. The second of two drugs approved by the FDA for dry eye disease, this medication is a welcome addition to the clinical armamentarium and a source of new hope for affected patients. Unlike topical lubricants, the two FDA-approved therapies for dry eye (Restasis and Xiidra) must be administered for a period of up to several months to achieve therapeutic effects.