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An inflammation of the lacrimal gland.
An inflammation of the lacrimal sac.
Dark Adaptation
The adjustment of the retina and iris (pupil) to decreased illumination.
Depth Perception
The ability to distinguish distance and volume of objects in a visual field.

An allergic reaction involving the conjunctiva and the surrounding skin.

Who can get it?
Anyone with allergies or sensitivities can get it. It is often caused by eyedrops such as anesthetics or glaucoma medications, or cosmetics. Perfume, jewelry, certain metals, soaps and detergents are also common triggers.

What are the symptoms?
Red eyes, redness of the surrounding skin, tearing, itching.

What is the treatment?
Treatment with prescription antihistamines is usually prescribed. Until you see your eye doctor, cold compresses and artificial tears may aid in reducing the discomfort.

A congenital mass (choristoma) consisting of skin and its dermal appendages.
A protrusion of Descemet's membrane through the floor of an ulcer.
Diabetes Mellitus

dye-a-BEE-teez mah lye'tuss

Diabetes is a disease in which the body is unable to produce and regulate insulin. Insulin is a chemical normally found in the blood and is needed to break down sugar in the bloodstream into a form that can be burned by a body in the form of energy. When there is not adequate insulin present the chemistry of the blood in the body is out of balance. When this happens, the health of the blood vessels begins to deteriorate. Soon the vessels begin to spring leaks. Blood and blood serum leeks into the surrounding tissue. When the defense system in the body tries to clean this mess up, more energy is needed, more blood is needed and more white blood cells are needed to go to work. Because the blood system is already having problems, the job is twice as hard to repair. At some point, when the clean up system is no longer able to keep up and the scar tissue has progressed to a point of no return, there begins a progressive shut down of the bodies systems.

The treatment for diabetes is fairly well understood. The best treatment is to reduce the demand on blood. That means losing weight. If there is less body weight to maintain, there is less need for the bodies natural supply of insulin. If weight control is not possible, then pills are used to assist in the lack of insulin. Ultimately, if none of these measures are holding the blood chemistry in check, then artificial Insulin is needed. Your doctor will help you carefully manage the insulin to achieve just the right balance to keep things as steady as possible. Remember this, the bad affects of diabetes increase faster the further into the disease one becomes. Therefore, it is extremely important to get proper control of the condition early on, while you still can.

Diabetic Complications:
The complications of diabetes can affect many parts of the body, including the kidneys, liver, legs and eyes. As far as the eyes are concerned the complications may include changes in present vision conditions (nearsightedness and farsightedness), glaucoma, cataracts, strabismus, decrease in corneal sensitivity, and diabetic retinopathy. It is important that diabetics monitor and maintain control of their condition regularly. While it has been stated that diabetics should consult with a physician regularly to help with the management of the blood chemistry, they should also consult with an Optometrist or Ophthalmologist to evaluate their eyes for the presence of DIABETIC RETINOPATHY. Diabetic Retinopathy is the number two cause of blindness today, so a routine examination is a good policy. The examination of the back of the eye (retina) can yield important information. By looking through the eyes pupil, the back of the eye becomes the only place in the body, a doctor can look at the blood vessels and blood flow, without cutting into some tissue. For this reason the information which is derived is not only important for evaluating the presence of Diabetic Retinopathy, but also is information which is usually typical of the vascular condition in the rest of the body. For example, if there are small hemorrhages in the back of the eye, there are probably hemorrhages in the liver and kidneys, as well. That information can be very useful to your regular physician as part of the total package of data needed to make good decisions regarding your overall diabetic condition, and the best treatment program for you.

Diabetic blindness

dye-ah-BEH-tik BLIND-ness

Blindness resulting from unchecked diabetic retinopathy.

Diabetic Retinopathy

dye' ah beh tik reh tih NOP a thee

Diabetic Retinopathy is a condition where a diabetic persons blood sugar gets too high. When this occurs, the high blood sugar level starts a series of events which end in damaged blood vessel walls.

Blood vessels in the eye are small and delicate. As such, the blood vessels in the eye are easily damaged. The damaged vessels can then leak fluid or bleed, causing the retina to swell and form deposits known as exudates.

Diabetic Retinopathy

There are two stages of development in Diabetic Retinopathy:

  • In Nonproliferative (Background) Retinopathy, there are tiny leaks. Sometimes they are such small leaks that a red blood cell can not even seep out. Unfortunately, the surrounding fluid can. When this occurs, there is unbalanced nutrition available to the delicate retinal nerves. the result is swelling In and under the retina. If this occurs In the central (macula) region, there may be a loss In vision. However, When this occurs In the peripheral retina, there is usually no significant vision loss noted.
  • In Proliferative Retinopathy, abnormal new and fragile blood vessels form on the retina and can lead to serious vision problems since the abnormal vessels are prone to break and bleed into the vitreous (a clear, jelly-like substance in the center of the eye). The vitreous then becomes clouded with blood and light cannot pass correctly through it to the retina, leading to blurred and distorted vision. Other complications can result if scar tissue develops from the abnormal blood vessels—retinal detachment can take place if the scar tissue pulls the retina from the back of the eye. Also, if the abnormal blood vessels begin to grow on the iris, glaucoma can form. Early diagnosis and treatment is essential.

What are the symptoms?:
Symptoms, while often not present, may include blurriness, blind spots or cloudiness in the vision. Laser and surgical treatments may be used to slow the progression and decrease the risk of vision loss.

What is the treatment?:
Laser surgery can be very helpful for the treatment of diabetic retinopathy. The laser beam can cauterize leaky spots, when focused on the retinal region to be treated. Additionally, the laser is sometimes used in a procedure called "Pan Retinal Photocoagulation" (PRP). Here, a portion of the peripheral retina is lasered in an effort to reduce the demand on oxygen. In this way, the laser stops the retina from calling for the growth of more new blood vessels ("neovascularization") to repair the damage. Those new blood vessels are not healthy vessels. They tend to leak even worse than the normal retinal vessels.

Additional keywords and misspellings:
diabetes diabetic retinal retinopath retinapathy

A unit of refractive power.

Double vision, or seeing two of everything, may be caused by a number of factors such as refractive error, cataracts or a misalignment of the eyes. Having double vision can seriously disrupt a person's daily activities.

To understand diplopia, you must first understand that In normal vision, both eyes look at the same object. The images seen by the two eyes are fused into a single picture by the brain. If the eyes do not point at the same object, the image seen by each eye is different and cannot be fused. The result is double vision, or diplopia.

Eyes may appear misaligned or crossed, or wander. However, these symptoms may not apply to all cases.

Treatment of diplopia or double vision may consist of eye exercises to strengthen the ocular muscles, surgical straightening of the eye, or both treatments. A non-surgical approach is Eye Therapy, which may be prescribed to re-align the misaligned eye and re-stimulate the part of the visual pathway to the brain which is not working correctly.

Additional keywords and misspellings:
dipplopia diplopea double vision duble two images

One eyelash of a second row of eyelashes; plural is distichiae.
The presence of two rows of cilia on one eyelid.
More than one cilium growing from a follicle.
DK Value
A measure of the oxygen transmitted by a contact lens material.

droo' zen

Drusen are tiny, white deposits which form between Bruch's membrane and the retinal pigment epithelium. Drusen are believed to be early warning signs of Age-related Macular Degeneration. Forms of drusen include optic nerve head drusen (ONHD), and dominant radial drusen. For a visual representation on drusen formation, click here for the website for the Center for the Study of Macular Degeneration.

Who can get it?
Drusen are common after age 60 and occur mostly in caucasians; drusen are sometimes an early sign of macular degeneration.

What are the symptoms?
Although most drusen have no symptoms, some people report a mild decrease of visual acuity and defects in the vision.

What is the treatment?
Drusen associated with macular degeneration can clear up with proper nutritional supplements such as antioxidants. Other forms of drusen may not respond to any type of therapy, so it's a good idea to check with your doctor about supplements. Avoid birth control pills or cortisone. Certain conditions that raise or significantly lower blood pressure can affect drusen. Some people with optic nerve ischemia are believed to have drops in blood pressure at night so it's a good idea not to take blood pressure medicines before bed.

Relaxation or biofeedback may help to improve circulation--many people with ocular blood flow problems tend to also have circulation problems to their hands. Check with your doctor for possible nutritional aids that can help with your circulation, such as fish oil capsules.

Additional keywords and misspellings:
congenitally elevated anomalous discs pseudopapilledema pseudoneuritis buried disc drusen disc hyaline bodies ONHD

Dry Eye

What Is Dry Eye?
Dry eye occurs when the normal flow of tears over the eyes is interrupted, or the tear film is abnormal.

How Are Tears Involved?
Tears are one of the body's natural mechanisms of defense. They are produced by the lacrimal glands in the eye and secreted to coat, protect and nourish the ocular surface.

Tears carry essential vitamins and nutrients across the surface of the eye. They also act as a shield against damaging factors such as wind, heat, smog or foreign particles. Normally, every time you blink, you add another protective coating of tears over the eyes.

What Are The Symptoms Of Dry Eye?
Dry eye symptoms can include one or more of the following conditions:

  • Burning and stinging
  • Scratchiness, grittiness or a "foreign body" sensation
  • Dryness
  • Itching
  • Sensitivity to bright light (photophobia)
  • Mucous secretions in the eye (mattering)

What Causes Dry Eye Symptoms?
There are a number of factors that can lead to dry eye. These include:

  • Reduction or loss of your eyes' ability to manufacture tears
  • Reduction or loss of the ability to blink adequately to fully coat the eye with tears
  • Preservatives contained in some bottled products for use in the eye, such as eyedrops or artificial tears. Frequent use of these products can aggravate dry eye conditions.
  • Eye infections
  • Wearing contact lenses
  • Medications
Consult your doctor to determine the possible causes for your particular dry eye condition.

How Do Medications Affect Dry Eye?
Some medications taken for arthritis, birth control, acne, colds, allergies or other medical conditions can cause the eyes to produce fewer tears than normal. Be sure to tell your eye care specialist about all of your current medications.

How Do I Know If I Have Dry Eye?
Your eye care specialist can readily determine if you have dry eye by performing a few simple tests.

Why Are My Eyes Better On Some Days Than Others?
Dry eye conditions are affected by a number of external environmental factors. Wind, heat and dry air can make dry eyes seem even worse. Wearing contact lenses can also aggravate dry eye.

Is There A Cure For Dry Eye?
There is no known cure for dry eye. However, some dry eye symptoms are caused by medications, eye infections or wearing contact lenses. In these cases, simply eliminating the cause of dry eye will stop the problem.

In many cases, however, dry eyes are a lifelong problem. You can relieve the symptoms, but not cure the original cause. Most eye care specialists recommend artificial tear products (ocular lubricants) for their patients with dry eyes. Follow your eye care specialist's recommendations in order to effectively relieve dry eye symptoms and avoid further damage to your eyes.

How Will Artificial Tears Help?
Artificial tears (ocular lubricants) can help relieve the symptoms of dry eye. They supplement natural tears and provide an artificial coating for the eyes.

However, some artificial tear products (those usually found in bottles) contain preservatives. Frequent use of preservatives in the eye can disrupt the integrity of natural tears and may cause dry spots on the eye. This, in turn, may make the eye more sensitive to those products.

If you are experiencing burning or stinging when using artificial tears, ask your eye care specialist to recommend a preservative-free tear product that is right for you.

Two Types Of Tears
Your eyes are lubricated by two different types of tears produced by the tear glands in your upper and lower eyelids.

Constant tears are continuously produced to lubricate the eye at all times, and contain natural antibiotics to fight infections.

Reflex tears are only produced in response to irritation, injury or emotion to help rinse the surface of the eye.

A delicate balance between constant and reflex tears, in addition to a satisfactory blink reflex, helps ensure that your eyes will be comfortable, well-lubricated and well-protected.

Five Common Causes Of Dry Eye Syndrome

  • Blinking: Blinking helps lubricate the eye by spreading tears across its surface. As you blink, tears are forced inward to the nose, where they flow into the tear drainage ducts, and drain into the nose and throat. If the tear drainage system is overactive, dry eye symptoms or related congestion of the nose, throat or sinus may occur.
  • Aging: Tear production decreases with age. In fact, the volume of lubricating constant tears can be as much as 60% less at age 65 than at age 18. This reduction in constant tear flow and resulting eye irritation may cause occasional excessive reflex tearing.
  • Environment: High altitudes; sunny, dry, windy conditions; and the use of heaters, blowers and air conditioners increase tear evaporation and reduce eye lubrication.
  • Contact Lenses: Contact lens wear can dramatically increase tear evaporation, causing irritation, infection, protein deposits, and pain. Research shows that dry eye is the lending cause of contact lens discomfort.
  • Medications: Some medications decrease the body's ability to produce lubricating tears. These include decongestants, antihistamines, diuretics, heart disease and ulcer prescriptions, antidepressants, anesthetics and drugs containing Beta Blockers.

Important Reminders For Dry Eye Sufferers
Among those who suffer from Dry Eye Syndrome and related tearing disorders, nearly half also experience related symptoms involving the nose, throat, and sinus. These include:

  • Nasal or sinus congestion, post nasal drip, and sneezing
  • Allergy and hay fever symptoms
  • Middle ear congestion
  • Chronic coughing
  • Headaches

Definition & graphics courtesy of The Vision Source!

Dry Eye (1)

Dry Eye is a condition in which the eye fails to produce an important component in its tears. The tears normally are composed of: water, mucoprotein and 1% salt along with some other minor components. Most of the time, what happens in dry eyes, is the eyes stop producing some of the mucoprotein. Mucoprotein is the slick substance in the eye tears. That's what keeps one's eyes from "squeaky" closings. Dry Eye is a major cause of Ocular Surface Disease.


Symptoms include irritated, dry and scratchy eyes; redness; blurred vision; overcompensation of tears; or the feeling of a foreign body in the eye. Mucoprotein in the tears is necessary to prevent damaging delicate eye tissues and possible scarring of the cornea. When there is inadequate mucoprotein possible treatments may include artificial tears which contain some type of lubricant to take the place of the missing mucoprotein. Two or three applications per day can be a big help. However, remember, like any lotion, the body and eye do not heal immediately, so expect 3 to 5 days of continued use of the drops before an improvement in the felling of the eyes occurs. Also keep in mind that this treatment regimen is permanent. Dry eye is a chronic condition. In other words, as soon as you stop the drops, 3 days to week later, the feeling of discomfort and scratchiness returns.

dry eye

Frequently a result of the natural aging process, dry eyes can also be caused by other problems such as medications, environment, certain health problems, or introduction of caustic substances to the eye.

An irregular pupil shape.
The Eye Encyclopedia is a collection of eye care terminology created by practicing optometrists and ophthalmologists. The information provided is not intended to be a substitute for regular medical care or to diagnose or treat any medical condition, and should be used only as a supplemental source of information. Please consult your doctor if you have any questions or concerns about your eye health.
The Eye Encyclopedia is a collection of eye care terminology created by practicing optometrists and ophthalmologists. The information provided is not intended to be a substitute for regular medical care or to diagnose or treat any medical condition, and should be used only as a supplemental source of information. Please consult your doctor if you have any questions or concerns about your eye health.