Etiology of Dry Eye

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What is Dry Eye?

• Dry eye is a reduction in your eye’s ability to produce sufficient natural tears.
• Insufficient tear production can lead to irritation and pain, and even scarring of the cornea (the transparent part of the eye that covers the pupil and iris).
• Many people will experience dry eye symptoms at some point in their lives.
• Often due to environmental factors such as indoor heating or air conditioning, it can also be caused by occupational factors such as prolonged computer use.
• Dry eye symptoms can affect anyone.
• Some of the symptoms of dry eye include a burning sensation or gritty feeling in the eyes. You might possibly also experience decreased tolerance to contact lens wear or sensitivity to light.

Patients with "dry eye": often complain of symptoms

• feeling of dryness
• gritty or foreign body sensation
• burning sensation and stinging 
• soreness
• tired eyes 
• paradoxically, watering eyes
• Tearing is reflex tearing from the irritated cornea stimulating the lacrimal gland. Your eye might possibly be red as a sign of irritation

Anatomy of the Tear Film

• The normal tear film has three layers and several key functions. The layers are 
  • Lipid which is the top most layer. This helps tears from evaporating and is made by meibomian glands. 
  • Aqueous which is in the middle. It is made from the main and accessory lacrimal glands 
  • Mucin which is next to the cornea, and allows the tear film to spread over the ocular surface; it is made from goblet cells

• The tear film is critical as it is the initially surface that light hits as it enters your eye. It provides the cornea with nutrients, oxygen and protection from infection.

Causes of Dry Eye

Many different things can cause dry eye syndrome. The normal aging of tear glands, as well as specific diseases and disorders, might possibly cause changes in the amount and condition of tears produced.

• Congenital (born with) - Riley-Day Syndrome (familial dysautonomia)

• Acquired

1.  
   1. Medications
      • decongestants
      • antihistamines
      • diuretics
      • beta-blockers
      • sleeping pills
      • pain-relievers
      • alcohol

   2. Trauma to lacrimal gland

   3. Neuroparalytic hypo secretion

   4. Inflammation of the lacrimal gland due to mumps, sarcoid

   5. Contact Lens Wear

   6. Milkulcz's syndrome

   7. Smoking

   8. Eye strain due to prolonged computer use

   9. Wearing contact lenses for long periods of time

2. Sjögren's syndrome

   • Sjögren's syndrome is an immune system disorder which is characterized by inflammation and dryness of the mouth, eyes, and other mucous membranes. Tear production might possibly be limited as the the lacrimal gland is affected. (Primary SS, young middle aged women, severe aqueous tear deficiency, HLA B8 association in 90% of patients

3. Excessive evaporation of tears can also cause dry eye syndrome. Such evaporation might possibly be caused by "meibomitis," which results from infection and inflammation of the meibomian glands in the eyelids. Patients with thyroid disease (Thyroid or Grave's disease results from overative thyroid which affects the eyes, might possibly cause proptosis, loss of vision and dry eye. Please see the Thryoid page for more details), might possibly also experience dry eye syndrome caused by excessive evaporation.

4. Decreased sensitivity of the cornea can also lead to insufficient production of tears.

5. Hormonal changes can also affect secretions from the tear glands.

What You Can Do to Prevent or Minimize Dry Eye Symptoms

• Avoid drafts from heating or air conditioning vents, especially in cars and airplanes.
• Take frequent breaks to relieve eye strain during periods of prolonged computer use.
• Remove your contact lenses and keep them especially clean when your eyes are feeling dry.
• After LASIK surgery, use artificial eye drops to soothe and comfort your dry eyes during recovery.
• Be aware that certain over-the-counter medications and prescription drugs can contribute to dry eye symptoms.
• Use a humidifier at home and in your workplace.