Vision Diseases, Disorders & Definitions
# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Behçet's Disease of the Eye:
Behçet's disease is an autoimmune disease that results from damage to blood vessels throughout the body, particularly veins. In an autoimmune disease, the immune system attacks and harms the body's own tissues.What causes Behçet's disease?
The exact cause is unknown. It is believed that an autoimmune reaction may cause blood vessels to become inflamed, but it is not clear what triggers this reaction.What are the symptoms of Behçet's disease?
Behçet's disease affects each person differently. The four most common symptoms are mouth sores, genital sores, inflammation inside of the eye, and skin problems. Inflammation inside of the eye (uveitis, retinitis, and iritis) occurs in more than half of those with Behçet's disease and can cause blurred vision, pain, and redness.
Other symptoms may include arthritis, blood clots, and inflammation in the central nervous system and digestive organs.
Bietti's Crystalline Dystrophy:
Bietti's crystalline corneoretinal dystrophy
Bietti's crystalline dystrophy (BCD) is an inherited eye disease named for Dr. G. B. Bietti, an Italian ophthalmologist, who described three patients with similar symptoms in 1937. The symptoms of BCD include: crystals in the cornea (the clear covering of the eye); yellow, shiny deposits on the retina; and progressive atrophy of the retina, choriocapillaries and choroid (the back layers of the eye). This tends to lead to progressive night blindness and visual field constriction. BCD is a rare disease and appears to be more common in people with Asian ancestry.
People with BCD have crystals in some of their white blood cells (lymphocytes) that can be seen by using an electron microscope. Researchers have been unable to determine exactly what substance makes up these crystalline deposits. Their presence does not appear to harm the patient in any other way except to affect vision.What causes Bietti's Crystalline Dystrophy?
From family studies, we know that BCD is inherited primarily in an autosomal recessive fashion. This means that an affected person receives one nonworking gene from each of his or her parents. A person who inherits a nonworking gene from only one parent will be a carrier, but will not develop the disease. A person with BCD syndrome will pass on one gene to each of his or her children. However, unless the person has children with another carrier of BCD genes, the individual's children are not at risk for developing the disease.
In September 2000, NEI researchers reported that the BCD gene had been localized to chromosome #4. In this region of chromosome #4 there are hundreds of genes. Researchers are now looking for which of the genes in this region of chromosome #4 causes BCD. Finding the gene may shed light on the composition of the crystals found in the corneas of patients with BCD and on what causes the condition.
Eyeglass lenses that incorporate two different refractive powers in each lens, usually for near and distance corrections.
Blending, by the brain, of the separate images seen by each eye into one composite image. Also, explained as the simultaneous use of the two eyes.
Blepharitis is a common condition that causes inflammation of the eyelids. The condition can be difficult to manage because it tends to recur.What causes blepharitis?
Blepharitis occurs in two forms:
Anterior blepharitis affects the outside front of the eyelid, where the eyelashes are attached. The two most common causes of anterior blepharitis are bacteria (Staphylococcus) and scalp dandruff.
Posterior blepharitis affects the inner eyelid (the moist part that makes contact with the eye) and is caused by problems with the oil (meibomian) glands in this part of the eyelid. Two skin disorders can cause this form of blepharitis: acne rosacea, which leads to red and inflamed skin, and scalp dandruff (seborrheic dermatitis).What are the symptoms of blepharitis?
Symptoms of either form of blepharitis include a foreign body or burning sensation, excessive tearing, itching, sensitivity to light (photophobia), red and swollen eyelids, redness of the eye, blurred vision, frothy tears, dry eye, or crusting of the eyelashes on awakening.What other conditions are associated with blepharitis?
Complications from blepharitis include:
- Stye: A red tender bump on the eyelid that is caused by an acute infection of the oil glands of the eyelid.
- Chalazion: This condition can follow the development of a stye. It is a usually painless firm lump caused by inflammation of the oil glands of the eyelid. Chalazion can be painful and red if there is also an infection.
Problems with the tear film: Abnormal or decreased oil secretions that are part of the tear film can result in excess tearing or dry eye. Because tears are necessary to keep the cornea healthy, tear film problems can make people more at risk for corneal infections.
Benign essential blepharospasm, hemifacial spasm.
Blepharospasm is an abnormal, involuntary blinking or spasm of the eyelids.What causes Blepharospasm?
Blepharospasm is associated with an abnormal function of the basal ganglion from an unknown cause. The basal ganglion is the part of the brain responsible for controlling the muscles. In rare cases, heredity may play a role in the development of blepharospasm.What are the symptoms of Blepharospasm?
Most people develop blepharospasm without any warning symptoms. It may begin with a gradual increase in blinking or eye irritation. Some people may also experience fatigue, emotional tension, or sensitivity to bright light. As the condition progresses, the symptoms become more frequent, and facial spasms may develop. Blepharospasm may decrease or cease while a person is sleeping or concentrating on a specific task.
Sightless area within the visual field of a normal eye. Caused by absence of light-sensitive photoreceptors where the optic nerve enters the eye.
Portions of this page are excerpted from Dictionary of Eye Terminology, copyright 1990-2006 by Barbara Cassin and Triad Communications. Reprinted with permission.
Some of the information above is reprinted from the National Eye Institute, National Institutes of Health, and is for educational purposes only. Superior Vision strongly recommends eye exams as the best way to diagnose eye conditions and learn more about potential vision problems.