Common Eye Diseases & Disorders
Note: The information below is reprinted from the National Eye Institute, 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.
Age-Related Macular Degeneration (AMD)
What is age-related macular degeneration?
Age-related macular degeneration (AMD) is a disease associated with aging that gradually destroys sharp, central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving.
AMD affects the macula, the part of the eye that allows you to see fine detail. AMD causes no pain.
In some cases, AMD advances so slowly that people notice little change in their vision. In others, the disease progresses faster and may lead to a loss of vision in both eyes. AMD is a leading cause of vision loss in Americans 60 years of age and older.
AMD occurs in two forms: wet and dry.
Where is the Macula?
The macula is located in the center of the retina, the light-sensitive tissue at the back of the eye. The retina instantly converts light, or an image, into electrical impulses. The retina then sends these impulses, or nerve signals, to the brain.
What is wet AMD?
Wet AMD occurs when abnormal blood vessels behind the retina start to grow under the macula. These new blood vessels tend to be very fragile and often leak blood and fluid. The blood and fluid raise the macula from its normal place at the back of the eye. Damage to the macula occurs rapidly.
With wet AMD, loss of central vision can occur quickly. Wet AMD is also known as advanced AMD. It does not have stages like dry AMD.
An early symptom of wet AMD is that straight lines appear wavy. If you notice this condition or other changes to your vision, contact your eye care professional at once. You need a comprehensive dilated eye exam.
What is dry AMD?
Dry AMD occurs when the light-sensitive cells in the macula slowly break down, gradually blurring central vision in the affected eye. As dry AMD gets worse, you may see a blurred spot in the center of your vision. Over time, as less of the macula functions, central vision is gradually lost in the affected eye.
The most common symptom of dry AMD is slightly blurred vision. You may have difficulty recognizing faces. You may need more light for reading and other tasks. Dry AMD generally affects both eyes, but vision can be lost in one eye while the other eye seems unaffected.
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Amblyopia (lazy eye)
What is amblyopia?
The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye.
How common is amblyopia?
Amblyopia is the most common cause of visual impairment in childhood. The condition affects approximately 2 to 3 out of every 100 children. Unless it is successfully treated in early childhood, amblyopia usually persists into adulthood, and is the most common cause of monocular (one eye) visual impairment among children and young and middle-aged adults.
What causes amblyopia?
Amblyopia may be caused by any condition that affects normal visual development or use of the eyes. Amblyopia can be caused by strabismus, an imbalance in the positioning of the two eyes. Strabismus can cause the eyes to cross in (esotropia) or turn out (exotropia). Sometimes amblyopia is caused when one eye is more nearsighted, farsighted, or astigmatic than the other eye. Occasionally, amblyopia is caused by other eye conditions such as cataract.
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Anophthalmia and Microphthalmia
Other Names
Anophthalmos and microphthalmos, small eye syndrome.
What are 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.
What causes anophthalmia and microphthalmia?
Causes of these conditions may include genetic mutations and abnormal chromosomes. Researchers also believe that environmental factors, such as exposure to X-rays, chemicals, drugs, pesticides, toxins, radiation, or viruses, increase the risk of anophthalmia and microphthalmia, but research is not conclusive. Sometimes the cause in an individual patient cannot be determined.
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Behçet's Disease of the Eye
Other Names
Adamantiades
What is Behçet's disease?
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 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.
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Bietti's Crystalline Dystrophy
Other names
Bietti's crystalline corneoretinal dystrophy
What is Bietti's Crystalline 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.
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Blepharitis
Other Names
Granulated eyelids.
What is blepharitis?
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.
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Blepharospasm
Other Names
Benign essential blepharospasm, hemifacial spasm.
What is Blepharospasm?
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.
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Cataract
What is a cataract?
A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Cataracts are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery.
A cataract can occur in either or both eyes. It cannot spread from one eye to the other.
What is the lens?
The lens is a clear part of the eye that helps to focus light, or an image, on the retina. The retina is the light-sensitive tissue at the back of the eye.
In a normal eye, light passes through the transparent lens to the retina. Once it reaches the retina, light is changed into nerve signals that are sent to the brain.
The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image you see will be blurred.
Are there other types of cataract?
Yes. Although most cataracts are related to aging, there are other types of cataract:
- Secondary cataract. Cataracts can form after surgery for other eye problems, such as glaucoma. Cataracts also can develop in people who have other health problems, such as diabetes. Cataracts are sometimes linked to steroid use.
- Traumatic cataract. Cataracts can develop after an eye injury, sometimes years later.
- Congenital cataract. Some babies are born with cataracts or develop them in childhood, often in both eyes. These cataracts may be so small that they do not affect vision. If they do, the lenses may need to be removed.
- Radiation cataract. Cataracts can develop after exposure to some types of radiation.
What causes cataracts?
The lens lies behind the iris and the pupil (see diagram). 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.
How can cataracts affect my vision?
Age-related cataracts can affect your vision in two ways:
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Clumps of protein reduce the sharpness of the image reaching the retina.
The lens consists mostly of water and protein. When the protein clumps up, it clouds the lens and reduces the light that reaches the retina. The clouding may become severe enough to cause blurred vision. Most age-related cataracts develop from protein clumpings.
When a cataract is small, the cloudiness affects only a small part of the lens. You may not notice any changes in your vision. Cataracts tend to "grow" slowly, so vision gets worse gradually. Over time, the cloudy area in the lens may get larger, and the cataract may increase in size. Seeing may become more difficult. Your vision may get duller or blurrier.
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The clear lens slowly changes to a yellowish/brownish color, adding a brownish tint to vision.
As the clear lens slowly colors with age, your vision gradually may acquire a brownish shade. At first, the amount of tinting may be small and may not cause a vision problem. Over time, increased tinting may make it more difficult to read and perform other routine activities. This gradual change in the amount of tinting does not affect the sharpness of the image transmitted to the retina.
If you have advanced lens discoloration, you may not be able to identify blues and purples. You may be wearing what you believe to be a pair of black socks, only to find out from friends that you are wearing purple socks.
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Corneal Disease
What is the cornea?
The cornea is the eye's outermost layer. It is the clear, dome-shaped surface that covers the front of the eye.
Refractive Errors
About 120 million people in the United States wear eyeglasses or contact lenses to correct nearsightedness, farsightedness, or astigmatism. These vision disorders--called refractive errors-- affect the cornea and are the most common of all vision problems in this country.
Refractive errors occur when the curve of the cornea is irregularly shaped (too steep or too flat). When the cornea is of normal shape and curvature, it bends, or refracts, light on the retina with precision. However, when the curve of the cornea is irregularly shaped, the cornea bends light imperfectly on the retina. This affects good vision. The refractive process is similar to the way a camera takes a picture. The cornea and lens in your eye act as the camera lens. The retina is similar to the film. If the image is not focused properly, the film (or retina) receives a blurry image. The image that your retina "sees" then goes to your brain, which tells you what the image is.
When the cornea is curved too much, or if the eye is too long, faraway objects will appear blurry because they are focused in front of the retina. This is called myopia, or nearsightedness. Myopia affects over 25 percent of all adult Americans.
Hyperopia, or farsightedness, is the opposite of myopia. Distant objects are clear, and close-up objects appear blurry. With hyperopia, images focus on a point beyond the retina. Hyperopia results from an eye that is too short.
Astigmatism is a condition in which the uneven curvature of the cornea blurs and distorts both distant and near objects. A normal cornea is round, with even curves from side to side and top to bottom. With astigmatism, the cornea is shaped more like the back of a spoon, curved more in one direction than in another. This causes light rays to have more than one focal point and focus on two separate areas of the retina, distorting the visual image. Two-thirds of Americans with myopia also have astigmatism.
Refractive errors are usually corrected by eyeglasses or contact lenses. Although these are safe and effective methods for treating refractive errors, refractive surgeries are becoming an increasingly popular option.
What are some diseases and disorders affecting the cornea?
Some diseases and disorders of the cornea are:
- Allergies
- Conjunctivitis (Pink Eye)
- Corneal Infections
- Dry Eye
- Fuchs' Dystrophy
- Herpes Zoster (Shingles)
- Iridocorneal Endothelial Syndrome
- Keratoconus
- Lattice Dystrophy
- Map-Dot-Fingerprint Dystrophy
- Ocular Herpes
- Pterygium
- Stevens-Johnson Syndrome
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Diabetic Eye Disease
What is diabetic eye disease?
Diabetic eye disease refers to a group of eye problems that people with diabetes may face as a complication of diabetes. All can cause severe vision loss or even blindness.
Diabetic eye disease may include:
- Diabetic retinopathy - damage to the blood vessels in the retina.
- Cataract - clouding of the eye's lens. Cataracts develop at an earlier age in people with diabetes.
- Glaucoma - increase in fluid pressure inside the eye that leads to optic nerve damage and loss of vision. A person with diabetes is nearly twice as likely to get glaucoma as other adults.
What is diabetic retinopathy?
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.
What are the stages of diabetic retinopathy?
Diabetic retinopathy has four stages:
- Mild Nonproliferative Retinopathy. At this earliest stage, microaneurysms occur. They are small areas of balloon-like swelling in the retina's tiny blood vessels.
- Moderate Nonproliferative Retinopathy. As the disease progresses, some blood vessels that nourish the retina are blocked.
- Severe Nonproliferative Retinopathy. Many more blood vessels are blocked, depriving several areas of the retina with their blood supply. These areas of the retina send signals to the body to grow new blood vessels for nourishment.
- Proliferative Retinopathy. At this advanced stage, the signals sent by the retina for nourishment trigger the growth of new blood vessels. This condition is called proliferative retinopathy. These new blood vessels are abnormal and fragile. They grow along the retina and along the surface of the clear, vitreous gel that fills the inside of the eye. By themselves, these blood vessels do not cause symptoms or vision loss. However, they have thin, fragile walls. If they leak blood, severe vision loss and even blindness can result.
How does diabetic retinopathy cause vision loss?
Blood vessels damaged from diabetic retinopathy can cause vision loss in two ways:
- Fragile, abnormal blood vessels can develop and leak blood into the center of the eye, blurring vision. This is proliferative retinopathy and is the fourth and most advanced stage of the disease.
- Fluid can leak into the center of the macula, the part of the eye where sharp, straight-ahead vision occurs. The fluid makes the macula swell, blurring vision. This condition is called macular edema. It can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses. About half of the people with proliferative retinopathy also have macular edema.
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Floaters
What Are Floaters?
Floaters are little "cobwebs" or specks that float about in your field of vision. They are small, dark, shadowy shapes that can look like spots, thread-like strands, or squiggly lines. They move as your eyes move and seem to dart away when you try to look at them directly. They do not follow your eye movements precisely, and usually drift when your eyes stop moving.
In most cases, floaters are part of the natural aging process and simply an annoyance. They can be distracting at first, but eventually tend to "settle" at the bottom of the eye, becoming less bothersome. They usually settle below the line of sight and do not go away completely. Most people have floaters and learn to ignore them; they are usually not noticed until they become numerous or more prominent. Floaters can become apparent when looking at something bright, such as white paper or a blue sky.
Floaters occur when the vitreous, a gel-like substance that fills about 80 percent of the eye and helps it maintain a round shape, slowly shrinks. As the vitreous shrinks, it becomes somewhat stringy, and the strands can cast tiny shadows on the retina. These are floaters.
Floaters are more likely to develop as we age and are more common in people who are very nearsighted, have diabetes, or who have had a cataract operation. There are other, more serious causes of floaters, including infection, inflammation (uveitis), hemorrhaging, retinal tears, and injury to the eye.
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. A retinal detachment is a serious condition and should always be considered an emergency. If left untreated, it can lead to permanent visual impairment within two or three days or even blindness in the eye. Those who experience a sudden increase in floaters, flashes of light in peripheral vision, or a loss of peripheral vision should have an eye care professional examine their eyes as soon as possible.
For people who have floaters that are simply annoying, no treatment is recommended. On rare occasions, floaters can be so dense and numerous that they significantly affect vision. In these cases, a vitrectomy, a surgical procedure that removes floaters from the vitreous, may be needed. A vitrectomy removes the vitreous gel, along with its floating debris, from the eye. The vitreous is replaced with a salt solution. Because the vitreous is mostly water, you will not notice any change between the salt solution and the original vitreous. This operation carries significant risks to sight because of possible complications, which include retinal detachment, retinal tears, and cataract. Most eye surgeons are reluctant to recommend this surgery unless the floaters seriously interfere with vision.
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Glaucoma
What is glaucoma?
Glaucoma is a group of diseases that can damage the eye's optic nerve and result in vision loss and blindness. Glaucoma occurs when the normal fluid pressure inside the eyes slowly rises. However, with early treatment, you can often protect your eyes against serious vision loss.
What is the optic nerve?
The optic nerve is a bundle of more than 1 million nerve fibers. It connects the retina to the brain. (See diagram below.) The retina is the light-sensitive tissue at the back of the eye. A healthy optic nerve is necessary for good vision.
What are some other forms of glaucoma?
Open-angle glaucoma is the most common form. Some people have other types of the disease.
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Low-tension or normal-tension glaucoma. Optic nerve damage and narrowed side vision occur in people with normal eye pressure. Lowering eye pressure at least 30 percent through medicines slows the disease in some people. Glaucoma may worsen in others despite low pressures.
A comprehensive medical history is important in identifying other potential risk factors, such as low blood pressure, that contribute to low-tension glaucoma. If no risk factors are identified, the treatment options for low-tension glaucoma are the same as for open-angle glaucoma.
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Angle-closure glaucoma. The fluid at the front of the eye cannot reach the angle and leave the eye. The angle gets blocked by part of the iris. People with this type of glaucoma have a sudden increase in eye pressure. Symptoms include severe pain and nausea, as well as redness of the eye and blurred vision. If you have these symptoms, you need to seek treatment immediately.
This is a medical emergency. If your doctor is unavailable, go to the nearest hospital or clinic. Without treatment to improve the flow of fluid, the eye can become blind in as few as one or two days. Usually, prompt laser surgery and medicines can clear the blockage and protect sight.
Congenital glaucoma. Children are born with a defect in the angle of the eye that slows the normal drainage of fluid. These children usually have obvious symptoms, such as cloudy eyes, sensitivity to light, and excessive tearing. Conventional surgery typically is the suggested treatment, because medicines may have unknown effects in infants and be difficult to administer. Surgery is safe and effective. If surgery is done promptly, these children usually have an excellent chance of having good vision.
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Secondary glaucomas. These can develop as complications of other medical conditions. These types of glaucomas are sometimes associated with eye surgery or advanced cataracts, eye injuries, certain eye tumors, or uveitis (eye inflammation). Pigmentary glaucoma occurs when pigment from the iris flakes off and blocks the meshwork, slowing fluid drainage. A severe form, called neovascular glaucoma, is linked to diabetes. Corticosteroid drugs used to treat eye inflammations and other diseases can trigger glaucoma in some people. Treatment includes medicines, laser surgery, or conventional surgery.
How does open-angle glaucoma damage the optic nerve?
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.
Sometimes, when the fluid reaches the angle, it passes too slowly through the meshwork drain. As 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.
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Histoplasmosis
What is histoplasmosis?
Histoplasmosis is a disease caused when airborne spores of the fungus Histoplasma capsulatum are inhaled into the lungs, the primary infection site. This microscopic fungus, which is found throughout the world in river valleys and soil where bird or bat droppings accumulate, is released into the air when soil is disturbed by plowing fields, sweeping chicken coops, or digging holes.
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.
How does histoplasmosis cause ocular histoplasmosis syndrome?
Scientists believe that Histoplasma capsulatum (histo) spores spread from the lungs to the eye, lodging in the choroid, a layer of blood vessels that provides blood and nutrients to the retina. The retina is the light-sensitive layer of tissue that lines the back of the eye. Scientists have not yet been able to detect any trace of the histo fungus in the eyes of patients with ocular histoplasmosis syndrome. Nevertheless, there is good reason to suspect the histo organism as the cause of OHS.
How does OHS develop?
OHS develops when fragile, abnormal blood vessels grow underneath the retina. These abnormal blood vessels form a lesion known as choroidal neovascularization (CNV). If left untreated, the CNV lesion can turn into scar tissue and replace the normal retinal tissue in the macula. The macula is the central part of the retina that provides the sharp, central vision that allows us to read a newspaper or drive a car. When this scar tissue forms, visual messages from the retina to the brain are affected, and vision loss results.
Vision is also impaired when these abnormal blood vessels leak fluid and blood into the macula. If these abnormal blood vessels grow toward the center of the macula, they may affect a tiny depression called the fovea. The fovea is the region of the retina with the highest concentration of special retinal nerve cells, called cones, that produce sharp, daytime vision. Damage to the fovea and the cones can severely impair, and even destroy, this straight-ahead vision. Early treatment of OHS is essential; if the abnormal blood vessels have affected the fovea, controlling the disease will be more difficult. Since OHS rarely affects side, or peripheral vision, the disease does not cause total blindness.
What are the symptoms of OHS?
OHS usually has no symptoms in its early stages; the initial OHS infection usually subsides without the need for treatment. This is true for other histo infections; in fact, often the only evidence that the inflammation ever occurred are tiny scars called "histo spots," which remain at the infection sites. Histo spots do not generally affect vision, but for reasons that are still not well understood, they can result in complications years--sometimes even decades--after the original eye infection. Histo spots have been associated with the growth of the abnormal blood vessels underneath the retina.
In later stages, OHS symptoms may appear if the abnormal blood vessels cause changes in vision. For example, straight lines may appear crooked or wavy, or a blind spot may appear in the field of vision. Because these symptoms indicate that OHS has already progressed enough to affect vision, anyone who has been exposed to histoplasmosis and perceives even slight changes in vision should consult an eye care professional.
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Low Vision
What is low vision?
Low vision means that even with regular glasses, contact lenses, medicine, or surgery, people find everyday tasks difficult to do. Reading the mail, shopping, cooking, seeing the TV, and writing can seem challenging.
Millions of Americans lose some of their vision every year. Irreversible vision loss is most common among people over age 65.
Is losing vision just part of getting older?
No. Some normal changes in our eyes and vision occur as we get older. However, these changes usually don't lead to low vision.
Most people develop low vision because of eye diseases and health conditions like macular degeneration, cataract, glaucoma, and diabetes. A few people develop vision loss after eye injuries or from birth defects. While vision that's lost usually cannot be restored, many people can make the most of the vision they have.
Your eye care professional can tell the difference between normal changes in the aging eye and those caused by eye diseases.
How do I know if I have low vision?
There are many signs that can signal vision loss. For example, even with your regular glasses, do you have difficulty:
- Recognizing faces of friends and relatives?
- Doing things that require you to see well up close, like reading, cooking, sewing, or fixing things around the house?
- Picking out and matching the color of your clothes?
- Doing things at work or home because lights seem dimmer than they used to?
- Reading street and bus signs or the names of stores?
Vision changes like these could be early warning signs of eye disease. Usually, the earlier your problem is diagnosed, the better the chance of successful treatment and keeping your remaining vision.
How do I know when to get an eye exam?
Regular dilated eye exams should be part of your routine health care. However, if you believe your vision has recently changed, you should see your eye care professional as soon as possible.
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Macular Hole
Other Names
Macular cyst, retinal hole, retinal tear, and retinal perforation.
What is a macular hole?
A macular hole is a small break in the macula, located in the center of the eye's light-sensitive tissue called the retina. The macula provides the sharp, central vision we need for reading, driving, and seeing fine detail.
A macular hole can cause blurred and distorted central vision. Macular holes are related to aging and usually occur in people over age 60.
Is a macular hole the same as age-related macular degeneration?
No. Macular holes and age-related macular degeneration are two separate and distinct conditions, although the symptoms for each are similar. Both conditions are common in people 60 and over. An eye care professional will know the difference.
What causes a macular hole?
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. Natural fluids fill the area where the vitreous has contracted. This is normal. In most cases, there are no adverse effects. Some patients may experience a small increase in floaters, which are little "cobwebs" or specks that seem to float about in your field of vision.
However, if the vitreous is firmly attached to the retina when it pulls away, it can tear the retina and create a macular hole. Also, once the vitreous has pulled away from the surface of the retina, some of the fibers can remain on the retinal surface and can contract. This increases tension on the retina and can lead to a macular hole. In either case, the fluid that has replaced the shrunken vitreous can then seep through the hole onto the macula, blurring and distorting central vision.
Macular holes can also occur from eye disorders, such as high myopia (nearsightedness), macular pucker, and retinal detachment; eye disease, such diabetic retinopathy and Best's disease; and injury to the eye.
What are the symptoms of a macular hole?
Macular holes often begin gradually. In the early stage of a macular hole, people may notice a slight distortion or blurriness in their straight-ahead vision. Straight lines or objects can begin to look bent or wavy. Reading and performing other routine tasks with the affected eye become difficult.
Are there different types of a macular hole?
Yes. There are three stages to a macular hole:
- Foveal detachments (Stage I). Without treatment, about half of Stage I macular holes will progress.
- Partial-thickness holes (Stage II). Without treatment, about 70 percent of Stage II macular holes will progress.
- Full-thickness holes (Stage III).
The size of the hole and its location on the retina determine how much it will affect a person's vision. When a Stage III macular hole develops, most central and detailed vision can be lost. If left untreated, a macular hole can lead to a detached retina, a sight-threatening condition that should receive immediate medical attention.
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Macular Pucker
Other Names
Epiretinal membrane, preretinal membrane, cellophane maculopathy, retina wrinkle, surface wrinkling retinopathy, premacular fibrosis, and internal limiting membrane disease.
What is a macular pucker?
A macular pucker is scar tissue that has formed on the eye's macula, located in the center of the eye's light-sensitive tissue called the retina. The macula provides the sharp, central vision we need for reading, driving, and seeing fine detail. A macular pucker can cause blurred and distorted central vision.
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.
However, sometimes when the vitreous pulls away from the retina, there is microscopic damage to the retina's surface (Note: This is not a macular hole). When this happens, the retina begins a healing process to the damaged area and forms scar tissue, or an epiretinal membrane, on the surface of the retina. This scar tissue is firmly attached to the retina surface. When the scar tissue contracts, it causes the retina to wrinkle, or pucker, usually without any effect on central vision. However, if the scar tissue has formed over the macula, our sharp, central vision becomes blurred and distorted.
What causes a macular pucker?
Most macular puckers are related to vitreous detachment, which usually occurs in people over age 50. As you age, you are at increased risk for macular pucker.
A macular pucker can also be triggered by certain eye diseases and disorders, such as a detached retina and inflammation of the eye (uveitis). Also, people with diabetes sometimes develop an eye disease called diabetic retinopathy, which can cause a macular pucker. A macular pucker can also be caused by trauma from either surgery or an eye injury.
What are the symptoms of a macular pucker?
Vision loss from a macular pucker can vary from no loss to severe loss, although severe vision loss is uncommon. People with a macular pucker may notice that their vision is blurry or mildly distorted, and straight lines can appear wavy. They may have difficulty in seeing fine detail and reading small print. There may be a gray area in the center of your vision, or perhaps even a blind spot.
Is a macular pucker the same as age-related macular degeneration?
No. A macular pucker and age-related macular degeneration are two separate and distinct conditions, although the symptoms for each are similar. An eye care professional will know the difference.
Can macular pucker get worse?
For most people, vision remains stable and does not get progressively worse. Usually macular pucker affects one eye, although it may affect the other eye later.
Is a macular pucker similar to a macular hole?
A macular pucker and a macular hole are different conditions, although they both result from the same reason: The pulling on the retina from a shrinking vitreous. When the "pulling" causes microscopic damage, the retina can heal itself; scar tissue, or a macular pucker, can be the result. If the shrinking vitreous pulls too hard, it can tear the retina, creating a macular hole, which is more serious. Both conditions have similar symptoms - distorted and blurred vision. Also, a macular pucker will not "develop" into a macular hole. An eye care professional will know the difference.
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Retinal Detachment
Other Names
Detached retina, and retinal tear.
What is retinal detachment?
The retina is the light-sensitive layer of tissue that lines the inside of the eye and sends visual messages through the optic nerve to the brain. When the retina detaches, it is lifted or pulled from its normal position. If not promptly treated, retinal detachment can cause permanent vision loss.
In some cases there may be small areas of the retina that are torn. These areas, called retinal tears or retinal breaks, can lead to retinal detachment.
What are the symptoms of retinal detachment?
Symptoms include a sudden or gradual increase in either the number of floaters, which are little "cobwebs" or specks that float about in your field of vision, and/or light flashes in the eye. Another symptom is the appearance of a curtain over the field of vision. A retinal detachment is a medical emergency. Anyone experiencing the symptoms of a retinal detachment should see an eye care professional immediately.
What are the different types of 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.
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Retinopathy of Prematurity (ROP)
Other Names
retrolental fibroplasia
What is retinopathy of prematurity?
Retinopathy of prematurity (ROP) is a potentially blinding eye disorder that primarily affects premature infants weighing about 2¾ pounds (1250 grams) or less that are born before 31 weeks of gestation (A full-term pregnancy has a gestation of 38–42 weeks). The smaller a baby is at birth, the more likely that baby is to develop ROP. This disorder—which usually develops in both eyes—is one of the most common causes of visual loss in childhood and can lead to lifelong vision impairment and blindness. ROP was first diagnosed in 1942.
How many infants have ROP?
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.
What causes ROP?
ROP occurs when abnormal blood vessels grow and spread throughout the retina, the tissue that lines the back of the eye. These abnormal blood vessels are fragile and can leak, scarring the retina and pulling it out of position. This causes a retinal detachment. Retinal detachment is the main cause of visual impairment and blindness in ROP.
Several complex factors may be responsible for the development of ROP. The eye starts to develop at about 16 weeks of pregnancy, when the blood vessels of the retina begin to form at the optic nerve in the back of the eye. The blood vessels grow gradually toward the edges of the developing retina, supplying oxygen and nutrients. During the last 12 weeks of a pregnancy, the eye develops rapidly. When a baby is born full-term, the retinal blood vessel growth is mostly complete (The retina usually finishes growing a few weeks to a month after birth). But if a baby is born prematurely, before these blood vessels have reached the edges of the retina, normal vessel growth may stop. The edges of the retina—the periphery—may not get enough oxygen and nutrients.
Scientists believe that the periphery of the retina then sends out signals to other areas of the retina for nourishment. As a result, new abnormal vessels begin to grow. These new blood vessels are fragile and weak and can bleed, leading to retinal scarring. When these scars shrink, they pull on the retina, causing it to detach from the back of the eye.
Are there different stages of ROP?
Yes. ROP is classified in five stages, ranging from mild (stage I) to severe (stage V):
- Stage I — Mildly abnormal blood vessel growth. Many children who develop stage I improve with no treatment and eventually develop normal vision. The disease resolves on its own without further progression.
- Stage II — Moderately abnormal blood vessel growth. Many children who develop stage II improve with no treatment and eventually develop normal vision. The disease resolves on its own without further progression.
- Stage III — Severely abnormal blood vessel growth. The abnormal blood vessels grow toward the center of the eye instead of following their normal growth pattern along the surface of the retina. Some infants who develop stage III improve with no treatment and eventually develop normal vision. However, when infants have a certain degree of Stage III and "plus disease" develops, treatment is considered. "Plus disease" means that the blood vessels of the retina have become enlarged and twisted, indicating a worsening of the disease. Treatment at this point has a good chance of preventing retinal detachment.
- Stage IV — Partially detached retina. Traction from the scar produced by bleeding, abnormal vessels pulls the retina away from the wall of the eye.
- Stage V — Completely detached retina and the end stage of the disease. If the eye is left alone at this stage, the baby can have severe visual impairment and even blindness.
Most babies who develop ROP have stages I or II. However, in a small number of babies, ROP worsens, sometimes very rapidly. Untreated ROP threatens to destroy vision.
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Usher Syndrome
What Is Usher Syndrome?
Usher syndrome is an inherited condition that causes
- A serious hearing loss that is usually present at birth or shortly thereafter
- Progressive vision loss caused by retinitis pigmentosa (RP)
RP is a group of inherited diseases that cause night-blindness and peripheral (side) vision loss through the progressive degeneration of the retina, the light-sensitive tissue at the back of the eye that is crucial for vision.
Researchers have described three types of Usher syndrome-type I, type II and type III.
- Individuals with Usher syndrome type I are nearly or completely deaf and experience problems with balance from a young age. They usually begin to exhibit signs of RP in early adolescence.
- Individuals with Usher syndrome type II experience moderate to severe hearing impairment, have normal balance, and experience symptoms of RP later in adolescence.
- Individuals with Usher syndrome type III are born with normal hearing but develop RP and then progressive hearing loss.
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Vitreous Detachment
What Is Vitreous Detachment?
Most of the eye's interior is filled with vitreous, a gel-like substance that helps the eye maintain a round shape. There are millions of fine fibers intertwined within the vitreous that are attached to the surface of the retina, the eye's light-sensitive tissue. As we age, the vitreous slowly shrinks, and these fine fibers pull on the retinal surface. Usually the fibers break, allowing the vitreous to separate and shrink from the retina. This is a vitreous detachment. In most cases, a vitreous detachment is not sight-threatening and requires no treatment.
As the vitreous shrinks, it becomes somewhat stringy, and the strands can cast tiny shadows on the retina that you may notice as floaters, which appear as little "cobwebs" or specks that seem to float about in your field of vision. If you try to look at these shadows they appear to quickly dart out of the way. One symptom of a vitreous detachment is a small but sudden increase in the number of new floaters. This increase in floaters may be accompanied by flashes of light (lightning streaks) in your peripheral, or side, vision. In most cases, either you will not notice a vitreous detachment, or you will find it merely annoying because of the increase in floaters.
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.
Although a vitreous detachment does not threaten sight, once in a while some of the vitreous fibers pull so hard on the retina that they create a macular hole or lead to a retinal detachment. Both of these conditions are sight-threatening and should be treated immediately. If left untreated, a macular hole or detached retina can lead to permanent vision loss in the affected eye. Those who experience a sudden increase in floaters or an increase in flashes of light in peripheral vision should have an eye care professional examine their eyes as soon as possible. The only way to diagnose the cause of the problem is by a comprehensive dilated eye examination. If the vitreous detachment has led to a macular hole or detached retina, early treatment can help prevent loss of vision.
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