Resources

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• Age-Related Macular Degeneration (AMD)

  In some people, AMD advances so slowly that vision loss does not occur for a long time. In others, the disease progresses faster and may lead to a loss of vision in one or both eyes. As AMD progresses, a blurred area near the center of vision is a common symptom. Over time, the blurred area may grow larger or you may develop blank spots in your central vision. Objects also may not appear to be as bright as they used to be.
  
  AMD by itself does not lead to complete blindness, with no ability to see. However, the loss of central vision in AMD can interfere with simple everyday activities, such as the ability to see faces, drive, read, write, or do close work, such as cooking or fixing things around the house.
  

• Amblyopia

  Amblyopia can result from any condition that prevents the eye from focusing clearly. Amblyopia can be caused by the misalignment of the two eyes—a condition called strabismus. With strabismus, the eyes can cross in (esotropia) or turn out (exotropia). Occasionally, amblyopia is caused by a clouding of the front part of the eye, a condition called cataract.
  
  A common cause of amblyopia is the inability of one eye to focus as well as the other one. Amblyopia can occur when one eye is more nearsighted, more farsighted, or has more astigmatism. These terms refer to the ability of the eye to focus light on the retina. Farsightedness, or hyperopia, occurs when the distance from the front to the back of the eye is too short. Eyes that are farsighted tend to focus better at a distance but have more difficulty focusing on near objects. Nearsightedness, or myopia, occurs when the eye is too long from front to back. Eyes with nearsightedness tend to focus better on near objects. Eyes with astigmatism have difficulty focusing on far and near objects because of their irregular shape.
  

• Anophthalmia and Microphthalmia

  Anophthalmia and microphthalmia are often used interchangeably. Microphthalmia is a disorder in which one or both eyes are abnormally small, while anophthalmia is the absence of one or both eyes. These rare disorders develop during pregnancy and can be associated with other birth defects.

• Astigmatism

  Astigmatism occurs when light is bent differently depending on where it strikes the cornea and passes through the eyeball. The cornea of a normal eye is curved like a basketball, with the same degree of roundness in all areas. An eye with astigmatism has a cornea that is curved more like a football, with some areas that are steeper or more rounded than others. This can cause images to appear blurry and stretched out.

• Behçet’s Disease of the Eye

  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 that 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

  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.
  

• 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.
  

• 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.

• Cataract

  The lens lies behind the iris and the pupil. It works much like a camera lens. It focuses light onto the retina at the back of the eye, where an image is recorded. The lens also adjusts the eye’s focus, letting us see things clearly both up close and far away.
  The lens is made of mostly water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it.
  
  But as we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract. Over time, the cataract may grow larger and cloud more of the lens, making it harder to see.
  
  Researchers suspect that there are several causes of cataract, such as smoking and diabetes. Or, it may be that the protein in the lens just changes from the wear and tear it takes over the years.

• Color Blindness

  Most of us share a common color vision sensory experience. Some people, however, have a color vision deficiency, which means their perception of colors is different from what most of us see. The most severe forms of these deficiencies are referred to as color blindness. People with color blindness aren’t aware of differences among colors that are obvious to the rest of us. People who don’t have the more severe types of color blindness may not even be aware of their condition unless they’re tested in a clinic or laboratory.

• Cornea and Corneal Disease

  Although the cornea is clear and seems to lack substance, it is actually a highly organized group of cells and proteins. Unlike most tissues in the body, the cornea contains no blood vessels to nourish or protect it against infection. Instead, the cornea receives its nourishment from the tears and aqueous humor (a fluid in the anterior portion of the eye) that fills the chamber behind it. The cornea must remain transparent to refract light properly, and the presence of even the tiniest blood vessels can interfere with this process. To see well, all layers of the cornea must be free of any cloudy or opaque areas.

• Diabetic Eye Disease

  Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness in American adults. It is caused by changes in the blood vessels of the retina.
  
  In some people with diabetic retinopathy, blood vessels may swell and leak fluid. In other people, abnormal new blood vessels grow on the surface of the retina. The retina is the light-sensitive tissue at the back of the eye. A healthy retina is necessary for good vision.
  
  If you have diabetic retinopathy, at first you may not notice changes to your vision. But over time, diabetic retinopathy can get worse and cause vision loss. Diabetic retinopathy usually affects both eyes.
  

• Dry Eye

  Dry eye can make it more difficult to perform some activities, such as using a computer or reading for an extended period of time, and it can decrease tolerance for dry environments, such as the air inside an airplane.
  
  Other names for dry eye include dry eye syndrome, keratoconjunctivitis sicca (KCS), dysfunctional tear syndrome, lacrimal keratoconjunctivitis, evaporative tear deficiency, aqueous tear deficiency, and LASIK-induced neurotrophic epitheliopathy (LNE).
  

• Floaters

  Sometimes a section of the vitreous pulls the fine fibers away from the retina all at once, rather than gradually, causing many new floaters to appear suddenly. This is called a vitreous detachment, which in most cases is not sight-threatening and requires no treatment.
  
  However, a sudden increase in floaters, possibly accompanied by light flashes or peripheral (side) vision loss, could indicate a retinal detachment. A retinal detachment occurs when any part of the retina, the eye’s light-sensitive tissue, is lifted or pulled from its normal position at the back wall of the eye.
  

• Glaucoma

  
  Several large studies have shown that eye pressure is a major risk factor for optic nerve damage. In the front of the eye is a space called the anterior chamber. A clear fluid flows continuously in and out of the chamber and nourishes nearby tissues. The fluid leaves the chamber at the open angle where the cornea and iris meet. (See diagram below.) When the fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye.
  
  In open-angle glaucoma, even though the drainage angle is “open”, the fluid passes too slowly through the meshwork drain. Since the fluid builds up, the pressure inside the eye rises to a level that may damage the optic nerve. When the optic nerve is damaged from increased pressure, open-angle glaucoma-and vision loss—may result. That’s why controlling pressure inside the eye is important.
  

• Histoplasmosis

  
  Histoplasmosis is often so mild that it produces no apparent symptoms. Any symptoms that might occur are often similar to those from a common cold. In fact, if you had histoplasmosis symptoms, you might dismiss them as those from a cold or flu, since the body’s immune system normally overcomes the infection in a few days without treatment.
  
  However, histoplasmosis, even mild cases, can later cause a serious eye disease called ocular histoplasmosis syndrome (OHS), a leading cause of vision loss in Americans ages 20 to 40.
  

• Hyperopia

  Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain. The brain interprets these messages into the images we see.

• Idiopathic Intracranial Hypertension

  The most common symptoms of intracranial hypertension are headaches and visual loss, including blind spots, poor peripheral (side) vision, double vision, and short temporary episodes of blindness. Many patients experience permanent vision loss. Other common symptoms include pulsatile tinnitus (ringing in the ears) and neck and shoulder pain.
  
  Intracranial hypertension can be either acute or chronic. In chronic intracranial hypertension, the increased CSF pressure can cause swelling and damage to the optic nerve—a condition called papilledema.
  
  Chronic intracranial hypertension can be caused by many conditions including certain drugs such as tetracycline, a blood clot in the brain, excessive intake of vitamin A, or brain tumor. It can also occur without a detectable cause. This is idiopathic intracranial hypertension (IIH).
  
  Because the symptoms of IIH can resemble those of a brain tumor, it is sometimes known by the older name pseudotumor cerebri, which means “false brain tumor.”
  

• Macular Hole

  There are three stages to a macular hole:
  1. Foveal detachments (Stage I). Without treatment, about half of Stage I macular holes will progress.
  2. Partial-thickness holes (Stage II). Without treatment, about 70 percent of Stage II macular holes will progress.
  3. Full-thickness holes (Stage III).
  

• Macular Pucker

  Most of the eye’s interior is filled with vitreous, a gel-like substance that fills about 80 percent of the eye and helps it maintain a round shape. The vitreous contains millions of fine fibers that are attached to the surface of the retina. As we age, the vitreous slowly shrinks and pulls away from the retinal surface. This is called a vitreous detachment, and is normal. In most cases, there are no adverse effects, except for a small increase in floaters, which are little “cobwebs” or specks that seem to float about in your field of vision.

• Myopia

  Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain. The brain interprets these messages into the images we see.

• Presbyopia

  Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) by the cornea and lens. The light is then focused directly on the retina, which is a light-sensitive tissue at the back of the eye. The retina converts the light-rays into messages that are sent through the optic nerve to the brain. The brain interprets these messages into the images we see.

• Refractive Errors

  The most common types of refractive errors are myopia, hyperopia, presbyopia, and astigmatism.
  
  Myopia (nearsightedness) is a condition where objects up close appear clearly, while objects far away appear blurry. With myopia, light comes to focus in front of the retina instead of on the retina.
  
  Hyperopia (farsightedness) is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience hyperopia differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant hyperopia, vision can be blurry for objects at any distance, near or far.
  
  Astigmatism is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye. This can cause images to appear blurry and stretched out.
  
  Presbyopia is an age-related condition in which the ability to focus up close becomes more difficult. As the eye ages, the lens can no longer change shape enough to allow the eye to focus close objects clearly.
  

• Retinal Detachment

  There are three different types of retinal detachment:
  
  Rhegmatogenous [reg-ma-TAH-jenous]—A tear or break in the retina allows fluid to get under the retina and separate it from the retinal pigment epithelium (RPE), the pigmented cell layer that nourishes the retina. These types of retinal detachments are the most common.
  
  Tractional—In this type of detachment, scar tissue on the retina’s surface contracts and causes the retina to separate from the RPE. This type of detachment is less common.
  
  Exudative—Frequently caused by retinal diseases, including inflammatory disorders and injury/trauma to the eye. In this type, fluid leaks into the area underneath the retina, but there are no tears or breaks in the retina.
  

• Retinitis Pigmentosa

  RP is an inherited disorder that results from harmful changes in any one of more than 50 genes. These genes carry the instructions for making proteins that are needed in cells within the retina, called photoreceptors. Some of the changes, or mutations, within genes are so severe that the gene cannot make the required protein, limiting the cellís function. Other mutations produce a protein that is toxic to the cell. Still other mutations lead to an abnormal protein that doesnít function properly. In all three cases, the result is damage to the photoreceptors.

• Retinoblastoma

  The disease usually occurs in children younger than 5 years and may be in one eye or in both eyes. In some cases the disease is inherited from a parent.
  
  Retinoblastoma is a serious, life-threatening disease. However, with early diagnosis and timely treatment, in most cases, a child’s eyesight and life can be saved.
  

• Retinopathy of Prematurity

  Today, with advances in neonatal care, smaller and more premature infants are being saved. These infants are at a much higher risk for ROP. Not all babies who are premature develop ROP. There are approximately 3.9 million infants born in the U.S. each year; of those, about 28,000 weigh 2¾ pounds or less. About 14,000-16,000 of these infants are affected by some degree of ROP. The disease improves and leaves no permanent damage in milder cases of ROP. About 90 percent of all infants with ROP are in the milder category and do not need treatment. However, infants with more severe disease can develop impaired vision or even blindness. About 1,100-1,500 infants annually develop ROP that is severe enough to require medical treatment. About 400-600 infants each year in the US become legally blind from ROP.

• Stargardt Disease

  Stargardt disease is an inherited disorder of the retina – the tissue at the back of the eye that senses light. The disease typically causes vision loss during childhood or adolescence, although in some forms, vision loss may not be noticed until later in adulthood. It is rare for people with the disease to become completely blind. For most people, vision loss progresses slowly over time to 20/200 or worse. (Normal vision is 20/20).

• Usher Syndrome

  Usher syndrome is the most common condition that affects both hearing and vision. A syndrome is a disease or disorder that has more than one feature or symptom. The major symptoms of Usher syndrome are hearing loss and an eye disorder called retinitis pigmentosa, or RP. Retinitis pigmentosa causes night-blindness and a loss of peripheral vision (side vision) through the progressive degeneration of the retina. The retina is a light-sensitive tissue at the back of the eye and is crucial for vision. As retinitis pigmentosa progresses, the field of vision narrows, a condition known as “tunnel vision,” until only central vision (the ability to see straight ahead) remains. Many people with Usher syndrome also have severe balance problems.

• Uveal Coloboma

  Uveal coloboma is a rare condition that is not always well documented. Depending on the study and where the study was conducted, estimates range from 0.5 to 2.2 cases per 10,000 births. Some cases may go unnoticed because uveal coloboma does not always affect vision or the outside appearance of the eye.
  
  Uveal coloboma is a significant cause of blindness. Studies estimate that 5 to 10 percent of blind European children have uveal coloboma or uveal coloboma-related malformations.
  

• Uveitis

  The term “uveitis” is used because the diseases often affect a part of the eye called the uvea. Nevertheless, uveitis is not limited to the uvea. These diseases also affect the lens, retina, optic nerve, and vitreous, producing reduced vision or blindness.
  
  Uveitis may be caused by problems or diseases occurring in the eye or it can be part of an inflammatory disease affecting other parts of the body.
  
  It can happen at all ages and primarily affects people between 20 ñ 60 years old.
  
  Uveitis can last for a short (acute) or a long (chronic) time. The severest forms of uveitis reoccur many times.
  

• Vitreous Detachment

  A vitreous detachment is a common condition that usually affects people over age 50, and is very common after age 80. People who are nearsighted are also at increased risk. Those who have a vitreous detachment in one eye are likely to have one in the other, although it may not happen until years later.

Source: National Eye Institute.