Dry Eye Disease occurs when the normal flow of tears over the eyes is interrupted, or the tear film is abnormal. It affects about 1 in 5 people. A normal tear film functions to protect the ocular surface by acting as a shield against wind, heat, foreign particles, and infection.
The tear film is simplified into three layers. The innermost layer is the Mucin layer which helps bind the watery layer of the tear film to the ocular surface. The middle layer is the Aqueous (watery) layer which comprises the bulk of the tear film. The outermost layer is the Lipid (oil) layer and its main function is to reduce evaporation.
What are the symptoms of DED?
There are a range of symptoms for DED, and in some cases particularly in patients with long-standing DED there may be no symptoms, as the ocular surface has been damaged significantly.
Here are some of the common symptoms:
Scratchiness, grittiness or a “foreign body” sensation
Sensitivity to bright light (photophobia)
Mucous secretions in the eye (can be soft, dry or string-like discharge)
Blurred or fluctuating vision
Rubbing eyes and feeling better afterwards
What are the causes of DED?
DED is a multifactorial disease. There are numerous causes. These include but are not limited to:
Digital device use
Low blinking rate
Heating/cooling systems (decreases humidity)
Poor diet (low water intake, excess caffeine and/or alcohol intake, low amounts of fatty acid intake, vitamin A deficiency, etc)
Preservatives contained in some bottled products for use in the eye, such as eyedrops or artificial tears. Frequent use of these products can aggravate dry eye conditions.
Gender (post menopausal females are a large risk group due to decrease in hormonal levels leading to loss of anti-inflammatory protection)
Changes in hormone (chronic androgen deficiency, menopause and hormone replacement therapy)
Cancer (systemic chemotherapy, radiation therapy)
Systemic disease (such as Diabetes, thyroid disease, rheumatoid arthritis, systemic lupus erythematosus, rosacea, hepatitis C infection, HIV infection, Sjogren’s syndrome, sarcoidosis) can lead to abnormal tear production
Dysfunction of the lacrimal (watery) gland
Dysfunction of the meibomian (oil) glands
Previous eye surgery (such as refractive laser surgery, corneal transplantation)
Previous eye injury (eg chemical burns) or infection
Irregularities of the conjunctival surface (outer white layer of eye) such as pingeculae or pterygia
Lid aperture and lid/globe disorders (leads to reduced ability to blink adequately to coat the ocular surface). Common conditions include stroke or Bell’s palsy which makes closing the eyelid difficult.
Contact lens wear
What are the signs of DED?
Your optometrist will diagnose Dry Eye by taking a thorough targeted history, as well as evaluate: