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Home | News | Links | How to Help | Contact Us | Search Patient Information: Glossary: Glossary of Terms
A The ability of the eye to change its focus from distant to near objects; a process achieved by the lens changing its shape. 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 [Browse Terms] [Top] AMSLER GRID TEST
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 [Browse Terms] [Top]
See, also, POSTERIOR CHAMBER. 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 [Browse Terms] [Top]
The International Uveitis Study Group classification schema for uveitis has been widely adopted for clinical and research purposes. It separates uveitis by anatomical location of the disease, according to the major visible signs, in the various segments of the eye: anterior uveitis, intermediate uveitis, posterior uveitis, and panuveitis. See, also, UVEITIS. Click and ReadA-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 [Browse Terms] [Top] Protein that is part of the body's immune system; it is produced in response to substances, usually foreign, known as antigens. The binding of antibodies to foreign substances facilitates their destruction. Click and ReadA-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 [Browse Terms] [Top] A substance recognized as foreign by the immune system. Click and ReadA-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 [Browse Terms] [Top] A person who has no lens inside their eye (whether their own or an artificial one) is aphakic. 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 [Browse Terms] [Top] AQUEOUS HUMOR, AQUEOUS FLUID (A-kwe-us)
The aqueous humor is a clear, watery fluid that flows between and nourishes the lens and the cornea. It is secreted by the ciliary epithelium, cells of the ciliary body, and leaves the eye through a passageway known as Schlemm's Canal. 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 [Browse Terms] [Top] ASTIGMATISM (uh-STIG-muh-tizm) 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 [Browse Terms] [Top] A healthy immune system produces substances called antibodies that help fight and destroy viruses, bacteria, and other foreign substances that invade the body. In autoimmune disorders, the immune system produces antibodies against the body's healthy cells and tissues. These antibodies, called autoantibodies ("auto" means self), contribute to the inflammation of various parts of the body, including, sometimes, the eye, causing damage and altering the function of target organs and tissues. In autoimmune diseases, the body harms its own healthy cells and tissues. This leads to inflammation and damage to various body tissues. In addition, some autoantibodies join with substances from the bodyÇs own cells or tissues to form molecules called immune complexes. A buildup of these immune complexes in the body also contributes to inflammation and tissue injury in people with some forms of autoimmune disorder. Thus autoimmune disease is a disease in which the immune system destroys or attacks the patient's own body tissue. Regardless of the form of autoimmunity, any autoimmune disease affecting the eye will require systemic (e.g., oral as opposed to local, topical, ocular) therapy; the components of the immune system reside not in the eye, but rather are systemic, and therefore, regulation of those components will require systemic therapy. Such therapy is typically designed to suppress the overly aggressive immune system, allowing the body to eventually re-regulate itself, with the result often being that after the patient has been kept on systemic medications to suppress the inappropriate immune response for a finite length of time (for example, one year), medication can then be tapered and stopped without recurrence of the autoimmune attack. Sometimes resumption of the attack does occur, in which case the patient must be re-treated. Click and Read
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 [Browse Terms] [Top] Under normal conditions, the immune system protects the body from diseases and infections by killing harmful "foreign" substances, such as germs, that enter the body. Autoimmunity is a condition in which the immune system mistakenly attacks and harms the body's own cells and tissues; this immune reaction is the basis of a variety of autoimmune diseases including some forms of uveitis, diabetes, rheumatoid arthritis, and systemic lupus erythematosus, among others. Uveitis on the basis of autoimmunity is the most common form of uveitis. Click and ReadA-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 [Browse Terms] [Top] Deposition of calcium in the cornea associated with degenerative corneal disease, high blood calcium levels and juvenile arthritis and chronic uveitis. 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 [Browse Terms] [Top] BIRDSHOT RETINOCHOROIDOPATHY (BSRC) Birdshot retinochoroidopathy is a chronic intraocular inflammatory disease affecting mainly the posterior segment of the eye. It is distinct from other forms of posterior uveitis because of a very characteristic clinical presentation and a strong association with HLA-A29.2 antigen. Its etiology remains unknown. An autoimmune mechanism is likely to play an important pathogenic role given the demonstration of retinal autoantigen reactivity and the very strong association with the human leukocyte antigen (HLA)-A29 phenotype unique to this disease. BSRC is an uncommon disease. In contrast to most other uveitic entities in which the onset of disease is in younger age groups, BSRC typically occurs during middle age, presenting at an average age of 50, with a range of between 35 and 70 years of age. The reason for this age shift is unclear. BSRC is found almost exclusively among whites, with a higher incidence in those of Northern European descent. An apparent gender preference is observed in some series, with women representing up to 70% of reported cases, whereas no significant predilection for sex is found in other series. Click and ReadA-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 [Browse Terms] [Top] Each eye looking at the same object sees a slightly different image. Binocular vision is the ability to fuse these two images into one and gives us the ability to perceive depth and judge distances. 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 [Browse Terms] [Top] BLEPHARITIS (INFLAMMATION OF THE EYELIDS)
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 [Browse Terms] [Top] 1) A small area of the visual field where the optic nerve enters the eye; occurs normally in all eyes. 2) Any gap in the visual field corresponding to an area of the retina where no visual cells are present; associated with eye disease. Click and ReadA-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 [Browse Terms] [Top]
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 [Browse Terms] [Top]
Inside the eye, there is a lens which helps us to focus on what we see. The lens is made mostly of water and protein. The protein is arranged to let light pass through and focus on the retina. Sometimes some of the protein clumps together and starts to cloud a small area of the lens.This cloudiness of the lens is called a cataract. Over time, the cataract may grow larger and cloud more of the lens as shown in the photograph below, making it more difficult to see. In the early stages, stronger lighting may lessen the vision problems caused by cataracts. At a certain point, however, surgery may be needed to improve vision. Cataract develops in patients with uveitis because of the uveitis itself and also because of the prolonged use of steroid medications. Cataract developing in an eye with a history of chronic or recurrent uveitis has historically been called cataracta complicata.
Photos courtesy of The Lighthouse Inc., (Lighthouse National Center for Vision and Aging) New York, NY Click and Read
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 [Browse Terms] [Top] See, EPIRETINAL MEMBRANE 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 [Browse Terms] [Top] CELLS, MEASURE OF UVEITIS ACTIVITY Cells are collections of white blood cells (leukocytes) in the anterior chamber of the eye where they can be observed on slit lamp examination floating in the convection currents of the aqueous humor. The number of cells in the anterior chamber can be counted in the narrow beam of light from the slit lamp. This forms the basis for grading the severity of inflammation at any given point in time. The amount of white blood cells is the measure of uveitis activity, and is scaled from 1 to 4, depending on the severity (1 being the least severe inflammation and 4 being the most severe inflammation).The right hand table is the grading of aqueous cells in anterior uveitis used at MEEI. Inflammatory cells in the anterior chamber are usually a result of inflammation of the iris.Cells are difficult to capture in photographs. See, also, FLARE.
Cells can also be observed in the vitreous on dilated examination. Inflammatory cell accumulation in the vitreous is the result of inflammatory process in other intraocular structures such as the ciliary body, retina, and choroid. Cells in the vitreous can be living or dead, and both can become immutably affixed to vitreous fibers. Only live, active cells are graded in the MEEI rating system. Vitreous cells are rated on a scale of 1-4 , as follows: 1/2+=1-10 cells. 1+=11-20 cells. 2+=20-30 cells. 3+=30-100 cells. 4+=grater than 100 cells. Other institutions use other rating systems to grade vitreous cells. 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 [Browse Terms] [Top] The blood vessel that carries blood into the eye; supplies nutrition to the retina. 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 [Browse Terms] [Top] The blood vessel that carries blood from the retina. 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 [Browse Terms] [Top] See visual acuity. 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 [Browse Terms] [Top] See IMMUNOSUPPRESSIVE CHEMOTHERAPY 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 [Browse Terms] [Top] CHOROID (KOR-oyd)
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 [Browse Terms] [Top] CHOROIDITIS (KOR-oyd-itis) Inflammation of the choroid, the middle layer of the eye composed of blood vessels that nourish the back of the eye. 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 [Browse Terms] [Top] CHRONIC DISEASE, CHRONIC ILLNESS An illness that lasts for a long time. With regard to uveitis, inflammation lasting greater than 3 months or which recurs intermittently. Chronic means that the inflammation is there all the time, every day, day in and day out, to one degree or other. Recurrent means that the inflammation may be gone for a while and then recur. 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 [Browse Terms] [Top]
The ciliary body is part of the uveal tract. In the diagram below, the uveal tract is shown in red (Iris, ciliary body, and choroid). The ciliary body is nourished by blood vessels which also supply the iris.
The ciliary body supports the lens through the zonules. 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 [Browse Terms] [Top] The ciliary muscles relax the zonules to enable the lens to change shape (become more spherical) for focusing at near. The ciliary muscles make the lens thicker so the eye can focus on nearby objects and thinner so the eye can focus on distant objects. See, also, CILIARY BODY. 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 [Browse Terms] [Top] The extensions or projections of the ciliary body that secrete aqueous humor. See, also, CILIARY BODY. 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 [Browse Terms] [Top] CLASSIFICATION OF UVEITIS WHY ARE THERE SO MANY DIFFERENT NAMES FOR UVEITIS?
Uveitis is inflammation inside the eye, specifically affecting one or more of the three parts of the eye that make up the uvea: the iris (the colored part of the eye), the ciliary body (behind the iris, responsible for manufacturing the fluid inside the eye) and the choroid (the vascular lining tissue underneath the retina). These structures, shown in the diagram in pink, are collectively known as the uveal tract. There are many different names for uveitis. Readers to this site, for example, may have been told that they have a condition known as iritis, or iridocyclitis, or uveitis, or plars planitis, or choroiditis, or retinitis, to name a few.The International Uveitis Study Group recommended a classification schema that has been widely adopted for clinical and research purposes. It separates uveitis by anatomical location of the disease, according to the major visible signs, in the various segments of the eye: anterior uveitis, intermediate uveitis, posterior uveitis, and panuveitis. The course of the disease can be be further described as acute, chronic (> 3 months duration), and recurrent. Classification of uveitis is important for the following reasons:
WHAT IS THE DIFFERENCE BETWEEN "UVEITIS" AND "OCULAR INFLAMMATORY DISEASE"? Uveitis is one type, or sub-group, of ocular inflammatory disease. The uveal tract is not the only place in the eye where Inflammation occurs. Inflammation can occur inside the eye itself, or in the tissue, nerves, muscles or structures that surround the eye. This comprises a large group of diverse diseases collectively known as ocular inflammatory disease (OID). Ocular immunologists specialize in treating all forms of ocular inflammatory disease. 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 [Browse Terms] [Top]
Cones are one type of specialized light-sensitive cells (photoreceptors) in the retina that provide sharp central vision and color vision. Also see rods. The retina contains approximately 6 million cones. The cones are contained in the macula, the portion of the retina responsible for central vision. They are most densely packed within the fovea, the very center portion of the macula. Cones function best in bright light and allow us to appreciate color. 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 [Browse Terms] [Top] CONJUNCTIVA (KAHN-junk-TY-vuh)
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 [Browse Terms] [Top] Conjunctivitis is an inflammation of the conjunctiva, the thin, transparent layer that lines the inner eyelid and covers the white part of the eye, the sclera. Click and ReadA-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 [Browse Terms] [Top] The ability to perceive differences between an object and its background. 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 [Browse Terms] [Top] CORNEA (KOR-nee-uh)  The cornea is the outer, transparent, dome-like structure that forms the anterior most part of the outer coat of the eye. Looking through the cornea, as through a window, one can see the iris, pupil, and anterior chamber. The cornea is part of eye's focusing system. Click and Read
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 [Browse Terms] [Top] CORTICOSTEROIDS (STEROID MEDICATIONS) Corticosteroids (kor-ti-koe-STER-oyds) (cortisone-like medicines) are prescribed medications used to provide relief for inflamed areas of the body, including the eyes. They lessen swelling, redness, itching, and allergic reactions. Corticosteroids are often used as part of the treatment for a number of different diseases, such as severe allergies or skin problems, asthma, arthritis, and eye inflammation. Your body naturally produces certain cortisone-like hormones that are necessary to maintain good health. Patients who do not produce enough of these hormones may have had the medication prescribed to help make up the difference. Corticosteroids are very strong medicines. In addition to their helpful effects in treating medical problems, they have side effects that can be very serious. Long-term use of steroid medications in the treatment of ocular inflammatory disease is associated with the formation of cataract, and, in some individuals, a rise in intraocular pressure that can lead to glaucoma, with irreversible damage to the optic nerve and loss of vision. Steroid use in eye care includes administration in eye drops, by injection and infusion, or as an oral medication taken daily. Because of the undesirable side effects of long-term use of steroid, patients with ocular inflammatory disease are advised to discuss the use of steroid-sparing treatments with their treating ophthalmologist BEFORE permanent structural damage to the eye occurs.
See, also, GLAUCOMA and CATARACT. Click and Read:
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 [Browse Terms] [Top] Cyclitis is inflammation of the ciliary body, the structure responsible for production of aqueous humor and for changes in the shape of the lens. See, also, IRIDOCYCLITIS. 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 [Browse Terms] [Top] See MACULAR EDEMA. 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 [Browse Terms] [Top] 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 [Browse Terms] [Top] A process by which the pupil is temporarily enlarged with special eye drops (mydriatic); allows the eye care specialist to better view the inside of the eye. 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 [Browse Terms] [Top] Tiny yellow or white deposits in the retina or optic nerve head. 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 [Browse Terms] [Top] DRY EYE (KERATOCONJUNCTIVITIS SICCA) Dry eye is a condition that can develop under many circumstances. Dry eye affects an estimated 10 million people or more in the United States alone. In some, it may be associated with underlying medical problems. The dry eye syndrome is caused by the alteration in one's natural tear film, a thin layer of tears protecting the surface of our eyes. Damage to the surface of the eyes (cornea and conjunctiva) is responsible for the symptoms of dry eyes. Dry eye symptoms may include irritated, scratchy, dry, uncomfortable or red eyes, a burning sensation or feeling of something foreign in your eyes and blurred vision. Excessive dry eyes may damage eye tissue, scar the cornea, and impair vision and make contact lens wear difficult.Dry eye is also known as keratoconjunctivitis sicca (KCS).Aside from the wearing of contact lenses, perhaps the most important cause of dry eye is the natural aging process. Ag age 65, the eye produces about 60% fewer tears than it did at age 18. But dry eye can also result from disruption of the blinking reflex, medications such as antihistamines, decongestants, and heart medications, vitamin A deficiency, and environmental factors (sun, wind, smoke, and air conditioners). Even low humidity or high atmospheric pressures can produce dry eye in some individuals. Autoimmune disease can also cause "dry eye" (see SJOGREN'S SYNDROME). Click and Read
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 [Browse Terms] [Top] The inner layer of cells on the inside surface of the cornea. 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 [Browse Terms] [Top] EPIRETINAL MEMBRANE (ERM) (MACULAR PUCKER)
An epiretinal membrane is, generally, a thin layer of collagen on the surface of the retina. It may occur spontaneously. It may occur after vitrectomy for detached retina. It may occur because of inflammation (uveitis). It usually occurs on or near the macula, and therefore affects vision.If it is extremely thin, some call it a "cellophane maculopathy" when it is on the macula. If it contracts (and collagen or scar tissue often does), it distorts the photoreceptors or light-sensing neural elements of the macula, producing "macular pucker". But even without contraction and pucker an ERM can and usually does affect vision. They almost never, ever disappear spontaneously. They can be removed surgically, ERM "peeling". This procedure is "high risk", i.e. one can end up worse off rather than improved after such surgery; imagine peeling Scotch tape (the ERM) off tissue paper (the macula). And, so most retinal surgeons who perform ERM peeling rarely attempt such an operation unless the patient's vision is pretty poor, say 20/80 or worse; each surgeon typically has his or her own criterion or "cut-off" level of vision below which the risk of surgery is deemed too great for the potential benefit to be gained. 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 [Browse Terms] [Top] The outermost layer of cells of the cornea and the eye's first defense against infection. 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 [Browse Terms] [Top] A thin layer of tissue containing many blood vessels that nourish the sclera. At the front of the eye, the episclera is covered by the conjunctiva. 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 [Browse Terms] [Top] Inflammation of the episclera, a membrane covering the sclera of the eye. The episclera is a thin layer of tissue containing many blood vessels that nourish the sclera. At the front of the eye, the episclera is covered by the conjunctiva. Episcleritis is a non-infectious inflammation of the episclera. Episcleritis is usually mild and rarely progresses to scleritis. Click and ReadA-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 [Browse Terms] [Top]
The eyelids also provide a mechanical barrier against injury, closing reflexively when an object comes too close to the eye. The reflex is triggered by the sight of an approaching object, the touch of an object on the surface of the eye, or the eyelashes being exposed to wind or small particles such as dust or sand. 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 [Browse Terms] [Top] Flare in the vitreous can also be observed and rated. See, also, CELLS. 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 [Browse Terms] [Top] Flashes are sensations of light, when no light is really there. They may appear as many tiny bright lights (like "sparklers") or like flashes of lightening. Flashes may occur when the vitreous jelly pulls on or tears the retina. These flashes usually last for only a second or so, but typically occur repeatedly. They may be more obvious with eye movement, or in a dark room. Anyone with flashers should be examined promptly by an ophthalmologist. The ophthalmologist will search carefully for retinal tears. Some people with migraine headaches may experience a different type of flash. These are usually shimmering, jagged lights that are present constantly for a period of fifteen minutes or so. They typically appear in the center of your field of vision, and progress slowly towards the edges of the visual field. A headache that is commonly throbbing, and on one side of the head, may follow the disappearance of the flashes. 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 [Browse Terms] [Top] See, also, VITRITIS.
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 [Browse Terms] [Top] FOVEA (FOH-vee-uh) The central part of the macula that provides the sharpest vision. 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 [Browse Terms] [Top] 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 [Browse Terms] [Top] |
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The
Amsler grid is used by physicians to detect small irregularities in
the central 20 degrees of the 
The
anterior chamber of the eye (1) is the space between the 
Anterior
uveitis means 
A
condition in which the surface of the 
Blepharitis
refers to an inflammation in the oily glands of the eyelid. This usually
results in swollen 
Bruch's
membrane, shown here in yellow, separates the blood vessels of the 
Today,
cataract surgery is safe and very effective. Although researchers are
learning more about cataracts, no one knows for sure what causes them.
The most common type of cataract is related to aging. More than half
of all Americans age 65 and older have a cataract. Scientists
think there may be several causes, including smoking and diabetes. Or,
it may be that the protein in the lens just changes as it ages. There
is also some evidence that cataracts are linked to certain vitamins
and minerals. The National Eye Institute (NEI) is doing a study to see
whether taking more of these substances prevents or delays cataracts.
The
picture on the right is of a subcapsular cataract. A subcapsular cataract
is often found in people taking 
The
choroid, shown here in bright red, lies between the 
The
ciliary body the structure behind the 
Cones
are one type of specialized light-sensitive cells (photoreceptors) in
the 
The
conjunctiva is the thin, transparent tissue that covers the outer surface
of the eye. It begins at the outer edge of the 
A
retinal detachment occurs when the 
Flare
is protein in the 
Floaters
appear as gray or black specks, strands, or "cobwebs" in front
of the eyes. As the eyes move, the floaters move too. They do not follow
your eye movements precisely, as they usually drift when the eyes start
or stop moving. Floaters are caused by particles, such as white
blood 
Flourescein
angiography (FLOR-uh-seen an-jee-AHG-ruh-fee) is a test to examine blood
vessels in the 
The
posterior part, or back, of the eyeball, which includes part of the