Normal Lubrication of the surface of an eye

There are two types of tears in the eye:

1. Tears that flow/spill out of the eye in response to emotions (like crying) or irritation, and
2. Tear film that lubricates the eye.
 
Normally the surface of an eye is lubricated by a tear film consisting of three layers:

a. an outer oily layer
b. a middle watery layer
c. an inner mucus layer 

The oily layer is produced by Meibomian glands   located at the edge of  eyelid. It keeps the surface of the eye smooth and reduces evaporation of tear film into the air.

The watery layer is secreted by small glands in the Conjunctiva. Conjunctiva is a thin and translucent   layer of skin (like the skin of lips) which covers the front white part of the eyeball called Sclera. The large Lacrimal (tear) gland also contributes to the The mucus layer is produced by a different group of glands in the Conjunctiva. It attaches the tear film to the eye. 

What is dry eye?

Dry eye is a condition where lubrication of the surface of the eye is insufficient. Dry eye occurs when produced quantity/quality of the tear film can not keep the eye lubricated and comfortable.

Who can develop dry eye?

Dry eye can be caused by the reduction in any of the three  layers. Dry eye can develop in the following categories of  predisposed individuals:
  1. Old age
  2. Post-menopausal women
  3. Systemic diseases like arthritis
  4. Computer users, especially for long hours
  5. Those working outdoors for long hours
What are the symptoms of dry eye?
  1. Stinging or burning of eyes
  2. Excessive irritation or sensitivity to smoke
  3. Stringy (tough) eye mucus discharge
  4. Increased tearing in response to irritation.
  5. Heaviness and discomfort of the eyes
How is dry eye diagnosed?
    1. Tear Film Breakup Time. It is diagnosed by slit lamp biomicroscopic examination.
    2. Schirmer’s Test: Schirmer’s strip is used to detect the quantity of tear production.
    3. Lid Margin Examination using slit lamp biomicroscope to diagnose meibomytis.
What is the treatment of dry eye?
  1. Precautions for predisposed individuals and patients with dry eye
  2. Avoiding exposure to wind
  3. Wearing wrap around glasses/helmet when outdoors
  4. Splashing water in eyes three times in a day
  5. Avoiding direct blow of air conditioner 
  6. Taking breaks every two hours when working at the computer
Medicines:
  1. Eye drops: Lubricating/ Artificial tears
  2. Lubricating eye ointments can be used at night
  3. Lid  massage:  to  improve  meibomian  gland function
Surgical: 

Preserving tears draining out of naso-lacrimal duct by plugging duct’s opening.