Dry Eyes
Tear Film Deficiency

Dry eyes is a term used to describe eyes that are not able to lubricate themselves adequately in a natural way, leading to dry spots on the eye's surface. This condition can develop in any person at any time, but it most often occurs in people over 50 years of age.

Paradoxically, some patients with tear film deficiency can have watery, running eyes. For the explanation of how this can be, continue reading.

The tear film, which covers the eyes is made up of three layers:

2) The middle water layer: This layer is the thickest of the three and consists of the watery tears with which people are most familiar. These tears lubricate the eye and also cleanse it by washing away irritating foreign particles. Watery tears are produced in two places. The tears that are shed in response to irritation and emotion are produced by small lacrimal glands located against the sockets, just above the eyes. The watery tears that lubricate the eye are produced by small lacrimal glands which are located in the conjunctiva (the protective membrane that lines the inside of the eyelids and covers the visible part of the eye).

3) The inner mucin layer: This layer of mucin is produced by small glands in the conjunctiva. The mucin makes it possible for watery tears to adhere to and spread evenly over the surface of the eye — helping to keep the eye moist.

Dry eye conditions usually occur when the inner mucin layer does not adequately cover the surface of the eye. Without a complete covering of mucin, the other two layers of tear film have difficulty adhering to the eye.

This drying of the inner mucin layer is usually a result of a natural decrease in tear production, which occurs in all people as they age. Almost everyone will experience drier eyes as they get older, but some people have more problems than others.

Some diseases, infections or other abnormal physical conditions can disrupt the normal tear production and cause problems. Blepharitis is an eyelid irritation, which may infect and plug the meibomian glands, thereby interrupting the production of the outer oily layer of tears. Injuries to the eyes can also damage the tear producing glands and reduce tear production. In addition, people who have recently undergone eye surgery may experience dry eyes for a limited time after eye surgery.

Environmental factors such as a dry climate, wind and air conditioning can contribute to the problem by drying the eyes excessively. These factors are particularly problematic for people who spend long periods of time in automobiles — since, the air in automobiles tends to be very dry and is blown past the eyes by air conditioners and heaters.

Sometimes, dry eyes are associated with allergies. Long term allergies may gradually decrease the quality of tear film by causing a gradual loss of the goblet cells (which secrete the inner mucin layer that helps to maintain uniform spread of the tear film). Long term contact lens wear can also contribute to the development of tear film deficiency both by duct irritation causing inflammation as well as the associated allergies or allergic type conditions they produce. Dry eyes may also be linked with arthritis in a condition known as Sjorgen's syndrome, in which the eyes, mouth and other areas of the body become dry in association with arthritic symptoms. Certain medications can also inhibit tear production and cause dry eyes. Radiation therapy for cancer around the eyes can also damage the tear-producing glands, resulting in inadequate tear film.

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Dry eye symptoms vary from person to person in accordance with the nature and extent of the problem. The following are some of the more common symptoms of 
dry eyes:

• Tiredness of eyes: Especially at the end of the day. All normal eyes become tired after a long period of use, but dry eyes tend to tire more quickly since small dry spots begin to form on dry eyes early in the day. Although blinking can clear these dry spots temporarily, only a long period of sleep can clear them completely. In addition to tiredness, dryness of the eye can also cause an aching or pressure feeling behind the eye. Some people experience this perplexing symptom; though, doctors are not sure what causes it. Eyelids may also become droopy because they are naturally inclined to close over irritated eyes.
  
  
• Redness: When eyes are irritated (because of dryness, foreign bodies or other causes), they turn red as the vessels in the conjunctiva increase their blood supply to deal with the problem.
  
  
• Light sensitivity: Irritated eyes are naturally more sensitive, so light can be particularly bothersome to tired eyes.
  
  
• Foreign body or burning sensation: Due to inadequate lubrication, small dry spots form on the surface of the eye. As air passes over the eye and as the lids blink, these dry areas become irritated, which may feel as though a foreign body is on the eye or as if the eye is burning.
  
  
• Blurriness of vision: Distorted vision can result from uneven lubrication of the corneal surface. The cornea (the eye's clear outer window) must be covered with an even tear film for clear vision. Dry areas do not focus light the same way as moist areas focus light, so images can become blurred.
  
  
• Excessive tearing (watery eyes): The lacrimal glands produce tears, which lubricate the eye and may be shed in response to irritation or emotion. Because a lack of moisture irritates the eye, the lacrimal glands increase their production of watery tears to attempt to compensate, but these watery tears are unable to lubricate the eye adequately if the other two components of tear film (the mucin layer and oily layer) are not working properly — resulting in an overflow of tears.
  
  
• Loss of luster: Eyes that are very dry lose the clear glassy appearance normally produced by an even tear film.
  
  
• Corneal deterioration: If extremely dry eyes are not treated, ulcers may form on the corneal surface. If left untreated, these ulcers can be very painful and lead to further deterioration of the cornea. If scarring of the cornea occurs, vision may be permanently lost.

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There is no known cure for most case of dry eyes, but usually, the condition can be controlled so that discomfort is reduced and clear vision can be maintained. In most cases, doctors will recommend a treatment program similar to what is 
described below.

• Blink often: Blinking often is something that people with dry eyes must make a conscious effort to do, especially when focusing on something for an extended period of time. Blinking is the only way to spread tear film over the eyes. When people are involved in activities such as reading, driving, sewing, using a computer or watching television, they tend to blink less frequently than normal, causing their eyes to dry and tire more quickly. Making a conscious effort to blink frequently can lessen the problem. In addition, many people have an incomplete blink — they unknowingly do not close their eyes all the way when they blink; therefore, it is important for people with dry eyes to remember to close their eyes completely when blinking.
  
  
• Conserve Natural Tears: As mentioned earlier, dry climates, wind, indoor heating, air conditioning and some other environmental factors tend to dry eyes more quickly than more humid conditions. Making an effort to conserve natural tears by avoiding direct contact with wind and fans is helpful. Maintaining a more humid home environment can also be beneficial. It is possible to increase a home's humidity by adjusting the humidity setting on a furnace humidifier, buying a portable humidifier that can be placed in any room or even setting out bowls of water around the home.
  
  Another way to help conserve natural tears is to wear glasses on a regular basis. Glasses that provide some side protection are particularly helpful. Even if a person does not need corrective lenses to focus properly, the consistent use of sunglasses while outdoors will help to reduce the evaporation of natural tears, acting much like a windshield on a car. Some people with extremely dry eyes have found some relief by moving to, or vacationing in, more humid climates.
  
  
• Use Artificial Tears: People with dry eyes should make the use of artificial tears a basic and regular treatment. Several types of artificial tears are available without a prescription in almost any pharmacy. These eye drops are made of harmless moisturizing substances, which are designed to cover the eyes with an enduring moisturizing film to compensate for the lack of natural tears. These artificial tears can be used as often as necessary.

  Remember, the watery portion of the artificial tears is the least important part of the tear film. The watery component is simply the carrier for the active component, which is usually some form of water-friendly molecule that stabilizes the tear film. You can sense the presence of this substance in the artificial tear by rubbing a drop between your finger and thumb — most will have a somewhat slippery feeling like saliva.

  Generally, people who only have occasional symptoms only need to use artificial tears when their eyes are bothering them. However, those who have moderate to severe cases of dry eyes should initially use artificial tears very frequently until their symptoms begin to diminish. Once the symptoms have become less irritating, the tears can be used less frequently. 
  
  The most common reason that artificial tears do not work in remedying dry eyes is that the artificial tears are not used frequently enough.  In order to determine if an artificial tear is of benefit, it should be used a minimum of six times a day — each meal time and approximately halfway in between meal times. Once you have determined that the artificial tear is helpful, you can increase or decrease the frequency of artificial tear drops as necessary. A suggested schedule for very dry eyes is to use the artificial tears on an hourly basis throughout the day. If a person is performing tasks that require visual concentration (such as reading, sewing or computer work), natural blink rate tends to decrease; therefore, unless a person can remember to maintain a sufficient blink rate, the artificial tears should be used every 15 to 30 minutes. Because artificial tears do not  contain medication, it is impossible to overdose on them or to damage the eye with them. It is important to note, it is not possible to become addicted to artificial tears; though, people with dry eyes come to appreciate the comfort artificial tears provide and so they tend to use artificial tears frequently.

  It is important that people with dry eyes remember to use their artificial tears regularly. One of the symptoms of dry spots on the eye can be excessive tearing, as the lacrimal glands overcompensate for chronic dryness. In order to break this cycle of dry eyes and then excessive tearing, it is imperative that the artificial tears be used frequently to keep the eyes lubricated and to prevent the production of unnecessary watery tears.

  Many brands of artificial tears are available, so people can experiment with different types to discover which kinds work best for them. Some brands contain preservatives, which may irritate some individuals' eyes. People whose eyes are sensitive to preservatives and those who use artificial tears frequently (more than five or six times a day) should look for artificial tears that do not contain preservatives. Preservative-free artificial tears tend to come in small, individual packets with several drops per packet. Once the seal on the packet has been broken, it should be kept in a clean place between uses.  This type of packet should also be thrown away at the end of the day. People who have questions about the kinds of artificial tears that would be appropriate for them should consult with their doctor or pharmacist.

  For more enduring relief, thicker artificial tears and moisturizing ointments are also available without a prescription. The ointment can distort vision temporarily, so it is best used just before retiring for the night. More recently, gel-type tears have become available for use — providing a relief level between that of a watery artificial tear formula and a thick ointment.

  Because there are so many types of artificial tears, it is useful for people with dry eyes to record the types they have used — including a brief note to indicate the strong or weak points of each type. If problems persist, this information will be helpful to the doctor or pharmacist providing care for the dry eye condition.
  

• Special Treatments: If dry eyes cannot be adequately controlled though these treatment suggestions, a thorough eye examination is necessary. If an unusual cause for the dryness is detected, the doctor will be able to provide some treatment options. Doctors may elect to use plugs for the little openings for tear drainage (the puncta). Usually, a temporary plug, which dissolves after a few days to weeks is used to test whether a more permanent plug would be helpful. In almost all cases, plugs can be removed, if necessary. In some cases, doctors may elect to perform a surgical technique to close a punctum permanently. With the drainage puncta sealed, either surgically or with plugs, tears may remain on the eyes longer. Besides artificial tears, doctors may prescribe anti-allergy drops or an anti-inflammatory medication. Some medications taken by mouth can also improve the tear film.