Dry eyes

People with dry eyes often experience burning, itching or irritated eyes that tend to worsen as the day goes by.  Other indicators include redness, scratchiness, excessive tearing and blurred vision that improves with blinking.  The eyes may become very sensitive to light. 

Dry eye syndrome is a common condition that usually affects both eyes.  Dry eyes are more common in pregnant women, women after menopause and older individuals.  More than 60% of people over the age of 65 are affected to some extent. 

People develop dry eye syndrome when the quantity (volume) and/or quality (chemical composition) of tear fluid changes. 

Our tear film consists of three layers, each with its own purpose:

• The oily layer; forms the outer layer of the tear film.  Its main purpose is to coat the tear surface and reduce evaporation of tears.
• The watery layer; makes up most of what we ordinarily think of as tears.  This middle layer cleanses the eye and washes away foreign particles or irritants.
• The mucous layer; forms the inner layer of the tear film.  Mucous allows the watery layer to spread evenly and adhere to the surface of the eye.  Without mucus, tears would not stick to the eye. 

By producing tears at a slow and steady rate, the eye constantly bathes itself.  All three layers of the tear film have to be in perfect balance to keep your eyes properly moistened and comfortable. 

It may not sound logical that dry eye could also cause excessive tearing, but think of it as the eye's response to discomfort.  If any of the two (inner and/or outer) layers responsible for keeping tears on the eye are not balanced, the eye becomes dry and irritated.  Eye irritation prompts the lacrimal gland to release a large volume of tears, overwhelming the tear drainage system.

Causes for dry eyes

• Decreased tear production; can result from normal ageing, auto-immune disorders like rheumatoid arthritis and Sjögren's syndrome, or from conditions that decreases sensation on the surface of the eye like diabetes, long-term contact lens wear, eye surgery, trauma to the fifth nerve and certain viruses. 
  
  Tear production can also decrease from vitamin A and essential fatty acids deficiencies, and medications such as antihistamines, decongestants, birth control pills, antidepressants and medication to lower blood pressure.
   
• Increased tear evaporation; can result from thyroid eye disease or from simply having large eyes.  Evaporation is directly proportional to surface area, therefore the bigger the eye surface area exposed to air, the greater the rate of evaporation of tears.
  
  Long-standing eyelid inflammation (called blepharitis) results in decreased function of the oil glands in the eyelid.  This is important because the oil produced by these glands coats the tear film, retarding evaporation like a biological wrap.
  
  Blinking helps us to keep our eyes moist.  When working at a computer, people can blink up to five times less than normal.  Having an air conditioner in your office can further increase tear evaporation, placing you at greater risk for dry eye problems.  

Self treatment
 

• Make an effort to blink frequently.
• If you suffer from only occasional tearing or dryness of the eyes, try over-the-counter artificial tears.  These drops can be used as often as necessary as they are just a lubricant and have no side effects.  Do not use ordinary eye drops for reducing redness; some can cause dry eyes.
• Hot compressing (with a warm towel) or eyelash cleaning to open blocked glands and allow healthy tear film production.
• Essential fatty acids (like Omega 3, 6, 7 and 9) in the diet are helpful in not only suppressing inflammation, for example in rheumatoid arthritis, blepharitis and the inflammation of the tear gland that causes decreased tear production in Sjögren's syndrome.  In addition, it has been found that these same essential fatty acids are used by the oil glands in the eyelid to produce a healthy tear oily layer.
• Vitamin A helps form and maintain healthy mucus membranes, therefore assisting in tear layer production.  

See your optometrist or doctor if: 

• You experience severe discomfort or itchiness.
• Your eyelids stick together when you wake in the morning. You may need antibiotics.
• The drops do not help after regular administration for several days.  You may need tiny plugs (called punctal plugs) in the corner of your eye to slow tear drainage.
• The problem persists for longer than a few weeks.  A doctor may need to establish if your dry eyes is one of the symptoms of another disease.

Reviewed by Ilse Homan, Optometrist, B. Optom (RAU) F.O. A (SA). Hobart Grove Centre, Bryanson, visitIM Optical.

Read more:
Macular degeneration
Eyesight and eye care basics
Can contact lenses block UV light?
 

Useful resources:

South African Optometric Association
Tel: 011 805 4517

South African National Council for the Blind
Tel: 012 452 3811

Retina South Africa
Tel: 011 622 4904

Ophthalmological Society of South Africa