Dry Eye Syndrome is a condition where the surface of the eye lacks sufficient moisture or lubrication. Our eye should always be covered in a thick, stable layer of fluid, which we call the tear film. The tear film is made up of three layers (oil, water and mucous) which together protect the eye surface, keeps our vision clear and our eyes feeling comfortable. Dry eye can result from our glands not secreting enough fluid, the existing fluid evaporating too quickly.
What are the symptoms of Dry Eye Syndrome?
Most commonly, people experience one or more oft he following symptoms.
- Heavy or fatigued sensations in the eyes
- Red eyes
- Blurred vision
- Watery eyes
In severe cases, ongoing damage to the front of the eye can result in inflammation and scarring, which can also result in vision loss.
What causes Dry Eye Syndrome?
Dry eyes can affect everybody of every age. It can be caused by environmental conditions, menopause, systemic conditions (such as diabetes, thyroid conditions, rheumatoid arthritis), medications, smoking, contact lens wear, and more recently there is a link between dry eyes and excessive computer use. In the case of too much screen time, people stop blinking as regularly while they stare at the screen. This means the moisture on the eye is evaporating, leaving the eye surface exposed and resulting in dry eye symptoms.
At a pathophysiological level, dry eye can be classified based on the tear secretion gland that is compromised. The two subtypes are Aqueous Deficient Dry Eye, and Evaporative Dry Eye.
Aqueous Deficient Dry Eye
The lacrimal gland sits within the upper and outer orbit of the eye. It is responsible for
secreting the watery component of the tear film, called Aqueous, which keeps the ocular surface moist and nourished. When the lacrimal gland does not produce enough aqueous, the lack of watery fluid on the eye surface causes dry eye. Aqueous Deficient Dry Eye can be caused by age, damage or trauma to the tear glands, viruses, and systemic conditions such as Sjogrens Syndrome, Sarcoidosis, Lymphoma, Hepatitis C, HIV and AIDS, Hemochromatosis, or Amyloidosis.
Evaporative Dry Eye
The meibomian glands sit along the upper and lower eyelid margins and secrete a substance called meibum. This is a lipid (oil) based fluid that is the tear component preventing evaporation of the tear liquid. If the meibomian glands are dysfunctional, and the tear film is missing the important lipid layer, it will evaporate too quickly and leave ocular surface dry and exposed. Evaporative Dry Eye is associated with increasing age, Meibomian Gland Dysfunction, Blepharitis, Rosacea, medications, allergies, or eyelid trauma or injury.
Blepharitis is an inflammatory condition of the eyelids. It is characterised by chronic redness, lid swelling, itching, flaking or crusting around the eyelash base, sticky eyelids, loss of eyelashes, and dry eye symptoms. Blepharitis has associations with atopic disease, rosacea, allergies, dermatitis, and demodex (eyelash mites). However, it is also associated with Meibomian Gland Dysfunction and Dry Eyes. In some cases, when Blepharitis and Dry Eye often occur together, it can be difficult to determine which is the primary condition.