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Conditions of the Eye

Amblyopia: is a condition that occurs in children when one eye has poorer vision than the other. If amblyopia is left untreated, a child’s vision will not develop correctly. The child’s brain, as it matures, will start “ignoring” the image coming from the bad eye. This causes vision in the affected eye to become even worse as the child becomes a teenager. Because amblyopia can result in permanent vision loss in one eye, it is important to have a child with amblyopia regularly tested by an eye doctor.

Astigmatism: is a common eye condition that’s easily corrected by eyeglasses, contact lenses or surgery. Astigmatism is characterized by an irregular curvature of the cornea. This is one type of refractive error. Astigmatism occurs in nearly everybody to some degree. For significant curvature, treatment is required. A person’s eye is naturally spherical in shape. Under normal circumstances, when light enters the eye, it refracts evenly, creating a clear view of the object. However, the eye of a person with astigmatism is shaped more like a football or the back of a spoon. For this person, when light enters the eye it is refracted more in one direction than the other, allowing only part of the object to be in focus at one time. Objects at any distance can appear blurry and wavy.

Blepharitis: is the medical term for inflammation of the eyelids. The word “blepharitis” is derived from the Greek word blepharos, which means “eyelid,” and the Greek suffix itis, which is typically used to denote an inflammation in English. Inflammation is a general term used to describe the process by which white blood cells and chemicals produced in the body protect us from foreign substances, injury, or infection. The normal body response of inflammation involves varying degrees of swelling, redness, pain, warmth, and change in function. Blepharitis is an inflammation of the eyelids, causing red, irritated, itchy eyelids, and the formation of dandruff-like scales on the eyelashes. It is a very common eye disorder with a wide variety of causes. It affects people of all ages. Although it may be uncomfortable, annoying, or unattractive, blepharitis is not contagious and generally does not cause any permanent damage to eyesight. The condition can be difficult to manage because it tends to recur. Another term for blepharitis is granulated eyelids. Angular blepharitis is a term used to describe blepharitis which primarily affects the outer corners of the eyelids.

Cataract: is an eye disease in which the clear lens of the eye becomes cloudy opaque, causing decrease in vision. Although the word cataract to describe this condition has been part of the English language only since the middle of the 16th century, the eye disease has been recognized and surgically treated since ancient times.The lens is a portion of the eye that is normally clear. It assists in focusing rays of light entering the eye onto the retina, the light-sensitive tissue at the back of the eye. In order to get a clear image onto the retina, the portions of the eye in front of the retina, including the lens, must be clear and transparent. Once light reaches the retina, the light initiates a chemical reaction within the retina. The chemical reaction, in turn, initiates an electrical response which is carried to the brain through the optic nerve. The brain then interprets what the eye sees.

In a normal eye, light passes through the transparent lens to the retina. The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image striking the retina will be blurry and the vision will be blurry. The extent of the visual disturbance is dependent upon the degree of cloudiness of the lens.
Most cataracts are related to aging. Cataracts are very common in older people. By age 80, more than half of all Americans either have some degree of cataract or have already undergone cataract surgery in one or both eyes. By age 95, this percentage increases to almost 100%. A cataract can occur in either or both eyes. Individuals with a cataract in one eye usually go on to develop a cataract in the other eye as well. A cataract is not contagious and cannot spread from one eye to the other or from person to person. Cataracts do not cause the eye to tear abnormally. They are neither painful nor make the eye itchy or red.

Although vision can be restored in most people with cataracts, age-related cataracts are still the most common cause of blindness in the world, primarily because many third-world nations lack appropriate surgical services.

As life span increases in the developed world due to modern technology and new methods of treatment of acute and chronic disease, the incidence of age-related cataracts will continue to increase.

Corneal Ulcer: is an open sore on the cornea, the clear structure in the front of the eye. The cornea overlies the iris, which is the colored part of the eye.
A corneal ulcer will often appear as a gray to white area on the normally transparent cornea. Some corneal ulcers may be too small to see without adequate magnification and illumination. See the first reference for pictures of a corneal ulcer. Most corneal ulcers are caused by infections. Bacterial infections cause corneal ulcers and are common in people who wear contact lenses. Bacteria can directly invade the cornea if the corneal surface has been disrupted. Some bacteria produce toxins that can cause ulceration of the cornea. Viral infections are also possible causes of corneal ulcers. Viruses that may cause corneal ulcers include the herpes simplex virus (the virus that causes cold sores) and the Varicella virus (the virus that causes chickenpox and shingles). Fungal infections can cause corneal ulcers and may occur with improper care of contact lenses or overuse of eyedrops that contain steroids.

Dry Eye Syndrome: is a very common condition that is characterized by a disturbance of the tear film. This abnormality may result in disruption of the ocular surface, causing a variety of symptoms and signs and interference with quality of life.To help keep the eyes comfortable and vision optimal, a normal, thin film of tears coats the eyes. Three main layers make up this tear film.The innermost layer is the thinnest. It is a layer of mucin (or mucus). This very thin layer of mucus is produced by the cells in the conjunctiva (the clear skin that lines the eye). The mucus helps the overlying watery layer to spread evenly over the eye.The middle (or aqueous) layer is the largest and the thickest. This layer is essentially a very dilute saltwater solution. The lacrimal glands under the upper lids and the accessory tear glands produce this watery layer. The function of this layer is to keep the eye moist and comfortable, as well as to help flush out any dust, debris, or foreign objects that may get into the eye. Defects of the aqueous layer are the most common cause of dry eye syndrome, also referred to as dry eye or keratoconjunctivitis sicca (KCS).

The most superficial layer is a very thin layer of lipids (fats or oils). These lipids are produced by the meibomian glands and the glands of Zeis (oil glands in the eyelids). The main function of this lipid layer is to help decrease evaporation of the watery layer beneath.

“Eye floaters” are deposits or condensation in the vitreous jelly of the eye. People use the term eye floaters to describe seeing floating spots within their vision when they look around. Eye floaters may be present in only one eye or both eyes.The structures in the front of the eye (the cornea and lens) focus rays of light onto the retina. Light focused onto the retina allows one to see. The light going to the retina passes through the vitreous humor, which is a jellylike material that occupies the back two-thirds of the eye. At birth and during childhood years, the vitreous gel is usually totally clear. Later in life, strands, deposits, or liquid pockets may develop within the vitreous jelly. Each of these strands casts a small shadow onto the surface of the retina, and these shadows may be perceived by the patient as eye floaters. As the eye moves from side to side or up and down, these strands, deposits, or pockets also shift in position within the eye, making the shadows move and appear to float or undulate. People describe eye floaters as spots, straight and curved lines, strings, or “O” or “C” shaped blobs. Some people see a single floater while others may think they see hundreds. The lines may be thick or thin, and they sometimes appear to be branched. To most people, they appear grey and darker in color than the background. The density of different eye floaters will vary within an individual eye. Eye floaters may be more noticeable under certain lighting conditions and be more apparent when looking at a bright sky. Floaters are rarely seen in situations with reduced illumination. Like fingerprints, no two people have exactly identical patterns of eye floaters. If a person has eye floaters in both eyes, the pattern of the eye floaters in each eye will be different. In any eye that has eye floaters, that pattern of eye floaters may also change over time. Eye floaters always appear darker than the background and cannot be seen in darkness or with the eyes closed. This is unlike flashes, which often are seen in the dark and with your eyes closed.

Hyperopia or Farsightedness: have difficulty focusing on objects close up, such as print in a book. More severe hyperopia would also cause problems with seeing objects in the distance clearly, such as highway signs. The occurrence of hyperopia increases with age; At least half of all persons over the age of 65 have some degree of farsightedness. Hyperopia is a refractive error, like astigmatism and nearsightedness (myopia). Having a refractive error means that light rays bend incorrectly into your eye to transmit images to the brain. Farsightedness occurs when light entering the eye focuses behind the retina, instead of directly on it. An abnormally flat cornea or short eye can cause the light to enter the eye this way. Hyperopia often runs in families. It is often present at birth; however, many children outgrow it.

Glaucoma: is a disease of the major nerve of vision, called the optic nerve. The optic nerve receives light-generated nerve impulses from the retina and transmits these to the brain, where we recognize those electrical signals as vision. Glaucoma is characterized by a particular pattern of progressive damage to the optic nerve that generally begins with a subtle loss of side vision (peripheral vision). If glaucoma is not diagnosed and treated, it can progress to loss of central vision and blindness. Glaucoma is usually, but not always, associated with elevated pressure in the eye (intraocular pressure). Generally, it is this elevated eye pressure that leads to damage of the eye (optic) nerve. In some cases, glaucoma may occur in the presence of normal eye pressure. This form of glaucoma is believed to be caused by poor regulation of blood flow to the optic nerve. Worldwide, glaucoma is the leading cause of irreversible blindness. In fact, as many as 6 million individuals are blind in both eyes from this disease. In the United States alone, according to one estimate, over 3 million people have glaucoma. As many as half of the individuals with glaucoma, however, may not know that they have the disease. The reason they are unaware is that glaucoma initially causes no symptoms, and the subsequent loss of side vision (peripheral vision) is usually not recognized.

Macular Degeneration: The macula is in the center of the retina, the light-sensitive layer of tissue at the back of the eye. The macula is responsible for central vision (straight-ahead vision). Degeneration of the macula occurs most often after the age of 60 years and is termed age-related macular generation (AMD). AMD is a painless condition. There are two types of AMD: dry AMD and wet AMD. Smoking, high blood pressure, obesity, a diet high in unsaturated fats and simple carbohydrates and lack of exercise all increase the risk of AMD. Early symptoms of dry AMD include slightly blurred vision, the need for more light for reading, and difficulty recognizing faces until very close to the person. A symptom of more advanced dry AMD is the presence of a blurred spot in the center of vision. An early symptom of wet AMD is the wavy appearance of straight lines. Dry AMD cannot be treated at present, but progression can be slowed through a healthy lifestyle and, in certain cases, through anti-oxidant vitamins. Injections into the eye of anti-angiogenic agents are successfully used in arresting or slowing wet AMD. Because of new therapies for the wet form of AMD, early diagnosis of wet AMD is particularly critical.

Myopia or Nearsightedness: affects 20% to 30% of the population, but this eye disorder is easily corrected with eyeglasses, contact lenses or surgery. People who have myopia or nearsightedness have difficulty seeing distant objects, but can see objects that are near clearly. For example, a person who is nearsighted may not be able to make out highway signs until they are just a few feet away. People who are nearsighted have what is called a refractive error. This means that the light rays bend incorrectly into the eye to transmit images to the brain. In people with myopia, the eyeball is too long or the cornea has too much curvature, so the light entering the eye is not focused correctly. Light rays of images focus in front of the retina, the light-sensitive part of the eye, rather than directly on the retina, causing blurred vision. Myopia runs in families and usually appears in childhood. Sometimes the condition plateaus, or sometimes it worsens with age.

Presbyopia:A part of the natural aging process of the eye, and can be easily corrected. Technically, presbyopia is the loss of the eye’s ability to change its focus to see objects that are near. It is not a disease. It’s as natural as wrinkles, and it affects everybody at some point in life. Presbyopia generally starts to appear around age 45. Presbyopia is often confused with farsightedness , but the two are different. Presbyopia occurs when the eye’s lens loses flexibility. Farsightedness occurs as a result of the shape of the eyeball, which causes light rays to bend incorrectly once they have entered the eye.

STY: (sometimes spelled stye) is a tender, painful red bump located at the base of an eyelash or under or inside the eyelid. A sty results from a localized infection of the glands or a hair follicle of the eyelid. The medical term for a sty is hordeolum (plural, hordeola).
The term external hordeolum refers to a sty that develops at the base of an eyelash (the hair follicle), whereas the term internal hordeolum refers to a sty that develops in a meibomian gland, a gland located on the underside of the eyelid that secretes an oily substance onto the eyeball. A sty is sometimes confused with a chalazion (see below), which is a cystor a specific type of scarring due to chronic inflammation arising in the meibomian glands of the eyelid. A chalazion may develop when the infection of a sty persists over time, resulting in scarring around the meibomian gland. In contrast to a sty, a chalazion is usually painless.

Subconjunctival Hemorrhage: The conjunctiva is a clear tissue that covers the white of the eye (the sclera) and lines the inside of both eyelids. A subconjunctival hemorrhage is blood that is located between the conjunctiva and the underlying sclera. The conjunctiva contains nerves and many small blood vessels. These blood vessels are usually barely visible but become larger and more visible if the eye is inflamed. These blood vessels are somewhat fragile and their walls may break easily, resulting in a subconjunctival hemorrhage (bleeding under the conjunctiva). A subconjunctival hemorrhage appears as a bright red or dark red patch on the sclera. Most subconjunctival hemorrhages are spontaneous without an obvious cause for the bleeding from normal conjunctival blood vessels. Since most subconjunctival hemorrhages are painless, a person may discover a subconjunctival hemorrhage only by looking in the mirror. Many spontaneous subconjunctival hemorrhages are first noticed by another person seeing a red spot on the white of your eye. Rarely there may be an abnormally large or angulated blood vessel as the source of the hemorrhage.
The following can occasionally result in a spontaneous subconjunctival hemorrhage:

  • Sneezing
  • Coughing
  • Straining/vomiting
  • Increasing the pressure in the veins of the head, as in weight lifting
  • Eye rubbing or inserting contact lenses
  • Certain infections of the outside of the eye (conjunctivitis) where a virus or a bacteria weaken the walls of small blood vessels under the conjunctiva
  • Medical disorder causing bleeding or inhibiting normal clotting

This information was taken from, and for more information on conditions of the eye, go to: http://www.medicinenet.com/subconjunctival_hemorrhage/article.htm