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.
Dry eye symptoms can affect anyone. Some of the symptoms of dry eye include a burning sensation or gritty feeling in the eyes. You also may experience decreased tolerance to contact lens wear or sensitivity to light. Patients with "dry eye" often complain of symptoms such feeling of dryness in their eyes, the feeling of a gritty or foreign body in the eye, burning sensation and/or stinging, soreness, tired eyes and, paradoxically, watering eyes.
Dry eye can be caused by a number of factors. These include environmental factors such as indoor heating or air conditioning, prolonged computer use, through the use of medication (decongestants, antihistamines, diuretics, beta-blockers, sleeping pills, pain-relievers or alcohol), through trauma to the lacrimal gland, using contact lenses, smoking, or from some medical syndrome.
Excessive evaporation of tears can also cause dry eye syndrome. Such evaporation may 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 overactive thyroid which affects the eyes, may cause proptosis, loss of vision and dry eye. Please see the Thryoid page for more details), may also experience dry eye syndrome caused by excessive evaporation. Decreased sensitivity of the cornea can also lead to insufficient production of tears. Hormonal changes can also affect secretions from the tear glands
Tearing is reflex tearing from the irritated cornea stimulating the lacrimal gland. Your eye may be red as a sign of irritation. 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 first surface that light hits as it enters your eye. It provides the cornea with nutrients, oxygen and protection from infection.
You can prevent or minimize dry eye by avoiding drafts from heating or air conditioning vents, especially in cars and airplanes, taking frequent breaks to relieve eye strain during periods of prolonged computer use, or removing your contact lenses and keep them especially clean when your eyes are feeling dry. After LASIK surgery, using artificial tear drops to soothe and comfort your dry eyes during recovery can help fend off dry eye.