Dry eye disease may not sound particularly intimidating but those who have experienced severe dry eye know that it can significantly impact quality of life. Think of stubbing your pinky toe – it doesn’t sound like much and pre-stub it’s all good until you jam it into the table leg, then you realize that it’s actually really painful.

A cross-sectional study conducted in 2017 found that over 16 million Americans are projected to have dry eye disease. That’s 16 million Americans living with discomfort of the eyes and compromised vision. The prevalence of dry eye increases with age and is more common in women than men.

Dry eye disease, abbreviated to DED, is one of the most commonly observed conditions in clinical practice, both in ophthalmology and optometry. It has been found to be a much more complex condition than the name suggests, and even more complex than a bruised pinky toe.

DED can present in a variety of ways. Symptoms include a sensation of dryness (surprise!), grittiness, the sensation of something being stuck in the eye, tired eyes, red eyes, stinging or burning, fluctuating vision, and the increased need to blink. It is now well known that there is a poor relationship between the symptoms a patient reports and the signs a clinician observes in practice, whether the patient feels their eyes are particularly dry but all dry eye test results are normal, or whether a patient hasn’t noticed their eyes are dry at all but the eyecare practitioner finds they are in fact beginning to resemble the Sahara Desert.

At a basic level, DED occurs because the eyes either do not produce sufficient tears or the components of the tear film that they do produce are of a poor quality. A clean, stable layer of tears over the surface of the eye, that transparent dome known as the cornea, is required both for good ocular comfort as well as stable vision. It is thought that the tear film is comprised of three components – a mucin layer, which binds the rest of the tear film to the surface of the cornea; a thick aqueous layer produced by the lacrimal glands, which makes up the watery part of tears (these are also the glands involved in the crying when you stub your toe); and an outer layer of lipids, which is produced by glands within the eyelid known as Meibomian glands and prevents the aqueous layer from evaporating too quickly. The most common subtype of DED is caused by dysfunction of these Meibomian glands and is subsequently known as evaporative dry eye.

So now down to the nitty gritty (no pun intended)…

What Actually Causes Dry Eye?

• Age. As mentioned previously, increasing age is known to be a risk factor for developing DED. One study found a prevalence of 8.4% in patients under 60 years of age compared to 19% in those over 80 years of age.
• Gender. Due to the role of hormones in the development of dry eye, women are found to be more prone to DED compared to men, particularly menopausal and post-menopausal women. The same study cited above found a prevalence of 11.4% in men and 16.7% in women.
• Autoimmune diseases. DED is found with increased prevalence in those suffering from autoimmune diseases such as Sjogren’s syndrome, rheumatoid arthritis, or lupus. Unfortunately for women, autoimmune diseases are also more common in the fairer sex.
• Medications. Certain medications are associated with altering tear production. These include antihistamines, antidepressants, hormonal medications such as the contraceptive pill or those to relieve menopausal symptoms, and some antihypertensive medications.
• Environment. Hot, dry, windy, or smoky environments can destabilize the tear film and promote tear evaporation. The presence of air-conditioning is also a common contributor to dry eye symptoms.

Other factors contributing to an increased risk of DED include contact lens wear, refractive surgery, cataract surgery, and prolonged computer use.

Now the million-dollar question…

How Does One Treat Dry Eye Disease?
Unfortunately, there is no one cure-all treatment for DED, being the complicated, multi-factorial condition it is. Artificial tears are a good place to start and most treatment plans will involve the use of some sort of ocular lubricant. These are generally seen as a “quick fix” and while they provide immediate symptomatic relief, will often not address the underlying cause of the dry eye. Look for modifiable environmental and lifestyle factors such as adjusting the air-conditioning, changing medications, or ceasing smoking.

In cases of Meibomian gland dysfunction and evaporative dry eye, encouraging these glands to get a move on will go a long way for treating DED. Traditionally this treatment has involved applying heat to the eyelids and then massaging them firmly to push out any oil blockages from the glands. More recently, the use of IPL laser (intense pulsed light) has been found to improve the function of the Meibomian glands although exactly how it does this is still not fully understood. Fish oils and flaxseed oils have also been found to improve the quality of the tear film and reduce the inflammation found in DED. In situations where an insufficient amount of aqueous is produced, a tiny plug may be inserted into the tear ducts to help retain the tears against the surface of the eye for a longer period of time. For very severe dry eye there also exists humidifying goggles but these probably are as convenient as wearing steel-toed boots (which of course will help with the pinky-toe stubbing).

Constant research is being pushed into the area of dry eye disease. While suffering from eyes with a surface like the Australian outback can be quite debilitating and significantly impact quality of life, new innovative treatments are constantly being developed and tested.

References
Prevalence of Diagnosed Dry Eye Disease in the United States Amongst Adults Aged 18 Years and Older. https://www.ncbi.nlm.nih.gov/pubmed/28705660

The Lack of Association Between Signs and Symptoms in Patients with Dry Eye Disease. https://journals.lww.com/corneajrnl/Abstract/2004/11000/The_Lack_of_Association_Between_Signs_and_Symptoms.2.aspx

Distribution of Aqueous-Deficient and Evaporative Dry Eye in a Clinic-Based Patient Cohort: A Retrospective Study. https://journals.lww.com/corneajrnl/Abstract/2012/05000/Distribution_of_Aqueous_Deficient_and_Evaporative.2.aspx

Facts About Dry Eye. https://nei.nih.gov/health/dryeye/dryeye

Dry Eye. https://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/dry-eye

Etiology, prevalence, and treatment of dry eye disease. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2720680/