Dry eye disease, also referred to as dry eye syndrome, or simply dry eye, is a chronic disease estimated to affect more than 26 million Americans. Dry eye can occur when eyes do not produce the necessary quantity or quality of tears. Well-lubricated and moisturized eyes are essential to eye comfort and health. Disruptions to the eye’s tear film due to dry eye can result in mild to severe irritation, inflammation, blurred vision, and even scarring of the eye’s surface. (All About Vision)

Read on to learn more about the tear film, the types of dry eye, and possible causes of dry eye symptoms.

The Tear Film

The tear film comprises three layers that work together to provide lubrication and nutrients to the front surface of the eye, as well as protect the eye from infection and environmental irritants: (All About Vision)

The Mucous Layer

The innermost layer of the tear film is made of mucous produced by goblet cells in the conjunctiva. This layer helps to anchor the tears and spread them evenly over the surface of the eye (All About Vision).

The Aqueous Layer

The middle and largest layer, the aqueous layer, is a diluted salt water solution produced by the lacrimal glands located in the eyelids. This layer provides the majority of the liquid we refer to as tears. It is also responsible for cleaning the eye and washing away particles and irritants (AAO).

The Lipid Layer

The outermost layer of the tear film is an oily layer made of lipids produced by the meibomian glands in the eyelids. This layer smooths the outside of the tear surface and helps to decrease evaporation of the aqueous layer (AAO).

These three layers work together to protect and moisturize the eye. A deficiency in any of the layers can lead to dry eye disease.

Types of Dry Eye

There are two main classifications of dry eye: aqueous tear deficiency (ATD) and evaporative dry eye (AAO).

Aqueous tear deficiency refers to a condition in which the lacrimal glands fail to produce sufficient fluid for the aqueous layer of the tear film (All About Vision).

Evaporative dry eye occurs when the meibomian glands fail to produce sufficient oil to protect the aqueous layer, causing tears to evaporate too quickly to adequately cleanse and moisturize the surface of the eye (All About Vision).

Causes of Dry Eye

Dry eye can affect anyone at any point in life, though it is known to present more frequently as people age and to affect women at nearly twice the rate of men, mostly due to natural hormonal changes (All About Vision).

Dry eye can be caused or exacerbated by a variety of factors, including environmental irritants, certain lifestyles and habits, changes to the body, or underlying diseases. Given the wide range of causes, dry eye varies significantly across the patient population—from cases that are limited and circumstantial, to others that are chronic and severe.

Underlying Conditions

Dry eye may be caused or made worse by existing conditions in the body that disrupt the normal process of tear production. Below are some of the most common conditions linked to dry eye (AAO 2014; AAO 2012):

• Diabetes
• Autoimmune disorders, including lupus and rheumatoid arthritis
• Thyroid issues
• Neurologic conditions including stroke, Bell’s palsy, and Parkinson’s disease
• Herpes simplex virus
• Sjogren’s syndrome

This list is not exhaustive, and the risk factors associated with each condition vary significantly. The link between Sjorgen’s and dry eye, however, is significant; according to the American Academy of Ophthalmology, one out of every ten patients diagnosed with clinically significant dry eye will also have Sjorgen’s Syndrome (AAO).

Hormonal

The natural decrease in hormones that occurs as a result of aging puts older people at greater risk for developing dry eye. In addition, common hormonal shifts that affect women, including menopause, pregnancy, and menstruation, make women more prone to symptoms of dry eye than men of the same age (AAO; AAO; AAO).

Medication

A variety of prescription and over-the-counter medications can cause symptoms of dry eye primarily by reducing tear production All About Vision; AAO; AAO).

These medications may include:

• Cold medicines
• Antihistamines for allergies
• Antidepressant and anti-anxiety medications
• Beta blockers
• Pain relievers
• Sleeping pills
• Diuretics
• Birth control pills

Environmental

People who live in dry, dusty, or windy climates are more likely to experience symptoms of dry eye. One study demonstrated that cases of dry eye increase in cities at high altitude and those with higher levels of air pollution (All About Vision). Sufferers of seasonal allergies may also experience concurrent dry eye (AAO). Not to be outdone, indoor climates can also exacerbate dry eye, especially through use of air conditioners, which may accelerate tear evaporation, and indoor heaters that lower air humidity (All About Vision). Airplane travelers—especially frequent fliers—may experience dry eye symptoms due to the extremely dry air within planes. In short, nowhere is safe! But keep in mind that we all experience occasional eye irritation from environmental factors, and isolated discomfort doesn’t necessarily indicate a chronic condition.

Lifestyle

Certain lifestyle habits can lead to dry eye or aggravate existing symptoms. One of the most egregious is smoking, which may cause dry eye and lead to other, more severe eye issues (All About Vision).

Excessive use of computers, smartphones, and tablets can lead to dry eye, as people tend to blink less often when using these digital devices. The lack of blinking accelerates tear evaporation, leading to symptoms of dryness (All About Vision). This decrease in blink rate can also accompany reading, painting, or any other activity requiring prolonged focus and effort from the eyes (AAO).

If not properly applied or removed, makeup can facilitate the development of evaporative dry eye syndrome by allowing irritants to enter the eye or by clogging the meibomian glands. Contact lens use, especially over a prolonged period of time, can also lead to dry eye symptoms. In fact, dry eye discomfort is one of the leading reasons why people discontinue contact lens use (All About Vision).

Finally, LASIK and other corneal refractive surgical procedures can worsen pre-existing dry eye symptoms or lead to their development post-operatively. Usually, these symptoms are temporary and will subside within a few weeks of the procedure (All About Vision).

Stay tuned for more information about dry eye disease in our three-party blog series.

Paragon BioTeck, Inc., offers a product portfolio for the diagnosis, management, and treatment of ocular conditions, including dry eye, as well as products to maintain proper eyelid hygiene. The ilast® Lid Hygiene System is scientifically formulated to soothe and moisturize the dry, irritated skin around the eye. Comfortear® Punctum Plugs and Comfortear® Lacrisolve™ 180 Absorbable Punctum Plugs provide occlusion therapy for the treatment of symptoms associated with dry eye disease, which may result from allergies, cataracts, or contact lens intolerance. Patients who are unsure whether dry eye treatment is right for them should talk with their eye doctor.

Citations:

• “Understanding Dry Eye Syndrome.” All About Vision. 2015.
• “What is Dry Eye?” American Academy of Ophthalmology. 2014.
• “Dry Eye Syndrome.” American Academy of Ophthalmology. 2014.
• “Are We Missing Dry Eye in Children?” American Academy of Ophthalmology. 2012.
• “A Quick Guide to Dry Eye.” American Academy of Ophthalmology. 2014.
• “Causes of Dry Eye.” American Academy of Ophthalmology. 2014.
• “Dry Eye Risk.” American Academy of Ophthalmology. 2014.
• “The link between seasonal allergens and dry eye.” American Academy of Ophthalmology. 2015.
• “Dry Eye Treatment: Getting Relief From Dry Eyes.” All About Vision. 2016.