Based on recent data from the National Health and Wellness Survey, more than 16 million U.S. adults have been diagnosed with dry eye disease, and it’s estimated that many more are undiagnosed, treating their symptoms with over-the-counter drops. Dry eye disease is progressive and multifactorial, characterized by tear film abnormalities that cause eye irritation, redness, glare, eye fatigue and blurred vision. Causes of dry eye disease include chronic blepharitis and meibomian gland dysfunction and can be triggered by a variety of factors including contact lens wear, antihistamines, prolonged digital device use, gender (it is more prevalent in women), aging and climate. Recent laboratory and clinical studies have indicated that inflammation in the lacrimal glands, meibomian glands, conjunctiva, cornea and aqueous tears plays a pivotal role in its development.
In 2007, Baudouin et al. proposed the concept of a “vicious cycle of inflammation” as a core driver in dry eye, and breaking the cycle was reported to be an important step in the treatment of dry eye. The inflammatory vicious cycle includes tear film instability, more concentrated tears, corneal/conjunctival cell death and inflammation in the ocular surface. Intrinsic and extrinsic factors cause stress to the ocular surface, which accelerates the cycle and, in turn, exacerbates dry eye. (Investigative Ophthalmology & Visual Science November 2018, Vol.59, DES192-DES199).
With chronic inflammation, various changes occur—loss of goblet cells which secrete the mucous layer of the tear film, limbal stem cell loss, aqueous tear deficiency, immune cell infiltration into the corneal stroma, decreased corneal endothelial cell density, corneal nerve loss and elevated cytokine (a protein that regulates inflammation) levels in the tears and aqueous humor. The cornea, lacrimal glands, tears, conjunctiva, iris and aqueous humor are anatomically close and alteration by disease of one can affect another.
Dry eye disease prevalence tripled between 2005 and 2012, according to Military Health System data, and with an aging population and increasing digital device use, we can expect it to continue to increase. In fact, dry eye disease already is reaching epidemic proportions in the U.S., according to The Eye Center at Southern College of Optometry. Current treatment options range from over-the-counter eye drops and artificial tears to surgery. Research continues, and recent advances have revealed the inflammatory process and its role in dry eye disease. Comprehensive assessment of dry eye based on inflammation will improve the selection of treatments and help break the vicious cycle of the disease.
• Linda Conlin
Pro to Pro Managing Editor