Answers to your questions about Dry Eye

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 The medical community has defined Dry Eye as:

“... a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities play etiological roles.”                                                     -Tear Film Ocular Society Dry Eye Workshop II (TFOS DEWS II), Definition and Classification Report, 2017

Our plain speech definition of Dry Eye:

Dry Eye is a disease of the tissues of the front surface of the eye caused by many different factors, characterized by a loss of balance to the tear film, and [often] accompanied by [signs and] symptoms of discomfort and visual disturbance…

Dry Eye is described as a "complex, multifactorial disease that cannot be characterized by a single process, sign or symptom." Meaning that Dry Eye often stems from several different interacting causes or influences occurring at the same time. (I often see four or more in most patients in my clinic.) These multiple interacting causes and influences create:

• A loss of balance to the tear film (tear film instability)
• An increased concentration of salts and other substances in the tears (hyperosmolarity) 
• Inflammation of the tissues of the front surface of the eye and the surrounding tissues of the eyelids. (ocular surface inflammation)
• Potential damage to these tissues as a result
• Abnormal firing of irritated corneal nerves (neurosensory abnormalities)

These characteristics are are largely responsible for the many signs and symptoms patients with Dry Eye Disease experience. 

Two main mechanisms describe and help to classify Dry Eye Disease clinically:

• Evaporative Dry Eye (EDE): occurs when there is an increase in tear evaporation
• Aqueous-Deficient Dry Eye (ADDE): occurs when there is a decrease in tear production

There are many subtypes of each classification based on the underlying cause. A combination of both EDE & ADDE may also occur at the same time. When this is the case, the person is said to have Mixed Mechanism Dry Eye. 

Studies show up to 30% of adults may have Aqueous-Deficient Dry Eye, while approximately 86% of adults experience symptoms of Evaporative Dry Eye. As you might imagine, the percentage of Evaporative Dry Eye is much higher in Arizona and desert environments due to low humidity, high heat, wind, and forced air from air conditioners and fans.

Dryness       Gritty sensation         Burning         Feeling of something in the eye

Irritation      Sandy sensation        Stinging         Poor vision quality (needing to blink to see better)

Redness      Light sensitivity          Itching           Significant discomfort/or inability to wear contacts

Watering     Film over vision         Discomfort    Inflammation                      

(If you or someone you know routinely experiences these ocular signs and symptoms, it is very important to seek further care with an eye care practionner well versed in Dry Eye Disease.)

• Ocular discomfort that affects the ability to function
• Vision fluctuations that affect the ability to function
• Excessive ocular redness and/or watering that becomes noticeable and embarrassing (Patients routinely express concerns about how ocular redness is often mistaken by others and incorrectly attributed to staying out late, not sleeping enough, or "partying," while excessive tearing is often mistaken as the person being overly emotional or crying when they are not. Patients experiencing these symptoms in excess often report fears how this affects them both personally and professionally.)

Factors that influence Aqueous-Deficient Dry Eye (decreased tear production):

• Underlying ocular conditions: Trachoma, Neurotrophic Keratitis
• Underlying medical conditions: autoimmune and rheumatologic conditions especially those that affect connective tissue (Sjogren's Syndrome, Rheumatoid Arthritis, Polyarteritis Nodosa, Systemic Lupus Erythematosis, Wegener's Granulomatosis, Systemic Sclerosis, Mixed Connective Tissue Disease), primary biliary cirrhosis, Sarcoidosis, Lymphoma, Viral Infections, Graft vs. Host Disease, Stevens-Johnson Syndrome, Pemphigus, Cicatricial or Mucus Membrane Pemphigoid, Diabetes Mellitus, Hormone changes and imbalances.
• Certain medications (topical & oral, OTC & Rx): hormone replacement therapy, antihistamines, decongestants, anti-depressants, high blood pressure medications, birth control, acne medications, and drugs for Parkinson’s disease are some of the most common. 
• Injury/Trauma: Radiation Injury, Chemical Injury, Trigeminal Nerve Injury.
• Corneal nerve desensitization: due to contact lens wear (especially in those who overuse and abuse their contact lenses) and refractive surgery (i.e. LASIK & PRK)
• Dehydration
• Increasing age

Factors that influence Evaporative Dry Eye (increased tear evaporation):

• Meibomian Gland Diseases: Meibomian Gland Dysfunction (MGD), Eyelid & Blink Abnormalities (i.e. the inability to close or seal the eyelids properly. This can be due to lid aging, genetics, trauma, lid surgeries, excessive rubbing/tugging on lids, and neurological causes such as Bell’s Palsy or a stroke)
• Local disease: Anterior blepharitis, ocular surface inflammation, contact lens wear
• Systemic skin conditions: Rosacea, Seborrheic Dermatitis, Atopic Dermatitis, Psoriasis
• Other systemic disease: Hypercholesterolemia, Rheumatoid Arthritis
• Chemical exposure: Retinoic Acid (think retinol, acne medications, and skin creams), Polychlorinated biphenols (low amounts in certain paints, inks, clothing, cosmetics), certain harsh preservatives in over-the-counter eye drops, multipurpose contact lens solutions, and prescription eye medications
• Certain medications: Accutane, for example, if taken for very short periods can decimate the meibomian glands
• Certain beauty products & practices: (i.e. lash growth serums), practices (i.e. eyelash extensions), and procedures (i.e. botox) used on or done to the eyelids: their use, misuse, and abuse
• Environmental stresses: low humidity, high heat, strong winds, forced air from fans or air conditioners as well as smoke or smog