Many eye diseases have no early symptoms. They may be painless, and you may see no change in your vision until the disease has become quite advanced.
A cataract is clouding of the lens of the eye. As protein fibers in the lens clump together, the clouding worsens and prevents some light rays from passing through the lens and reaching the retina, the light-sensitive membrane that lines the inside of the back of the eye. Because cataracts usually develop very slowly, early vision changes may not be noticeable. However, as the cataract grows denser, the person’s vision gradually worsens. Cataracts usually do not cause pain.
There are several different types of cataracts. Congenital cataracts are present from birth, or cataracts may develop during childhood. In adults, the most common type of cataract is an age-related cataract, which can begin to develop when a person is in his or her 40s or 50s. Most cataracts are age-related. Another type of cataract is a secondary cataract, which usually develops in people with a chronic disease, especially diabetes. A traumatic cataract is a cataract that develops as a result of an eye injury.
If you have a cataract, the doctor will work with you to determine the best course of treatment. In the early stages of a cataract, prescription glasses (bifocals), a magnifying glass for reading or other activities that require you to see things close up, or stronger lighting at home or at work may help you see better. However, when such measures are no longer helpful, your doctor probably will recommend surgery to remove the clouded lens and implant a substitute lens. If cataract surgery is an option, the doctor will explain the risks and benefits of the surgery.
Glaucoma is a group of eye diseases in which damage to the optic nerve leads to loss of vision. The most common type of glaucoma, called chronic open-angle glaucoma, usually develops gradually over a number of years. A clear, watery liquid called aqueous fluid flows in and out of a small space at the front of each eye (the anterior chamber) to bathe and nourish nearby tissues and remove wastes. In chronic open-angle glaucoma, the drainage angle (the channel through which aqueous fluid drains from the eyeball) malfunctions and the fluid does not drain properly, causing the normal pressure inside the eye to slowly rise. If not controlled, this abnormally high pressure can permanently damage the optic nerve and other parts of the eye, causing vision loss and, eventually, blindness.
In chronic open-angle glaucoma, the drainage angle malfunctions and the aqueous fluid does not drain properly. As the fluid builds up, pressure inside the eyeball increases, potentially causing permanent damage to the optic nerve and other parts of the eye.
In acute closed-angle glaucoma, the entrance to the drainage angle becomes blocked, causing a sudden, severe increase in pressure inside the eyeball. Acute closed-angle glaucoma is a medical emergency that requires immediate medical treatment to clear the blockage and prevent blindness.
Although damage to the optic nerve caused by chronic open-angle glaucoma is permanent, treatment with medication and surgery can usually slow the disease or prevent it from progressing. An ophthalmologist will prescribe medication, usually given in eyedrops, that either reduces the pressure inside the eyeballs by slowing the flow of fluid into the eyes or improves fluid drainage from the eyes. Because pills may produce more serious side effects, they are prescribed only if the eyedrops are ineffective. You will need to take the medication for the rest of your life to control the pressure in your eyes. If the drugs lose their effectiveness over time or cause unpleasant side effects, a doctor may change the dosage or prescribe a different medication.
To treat chronic open-angle glaucoma that cannot be controlled with medication, the doctor can use a laser (a highly concentrated beam of light) to alter the shape of the drainage angle to make it easier for fluid to drain from the eye. This painless procedure usually is performed in the doctor’s office or in an outpatient facility. In some cases, the effects of laser surgery may wear off over time and the procedure must be repeated. If glaucoma cannot be controlled with medication or laser surgery, an ophthalmologist may recommend a surgical procedure called trabeculectomy, in which an alternate outlet for aqueous fluid is created to lower the pressure inside the eyeball. This type of surgery is performed in a hospital.
Emergency treatment for acute closed-angle glaucoma involves a brief, painless surgical procedure called iridotomy. In this procedure, the doctor usually uses a laser to create a small drainage hole in the iris to change the shape of the structure of the eye and help fluid drain from the eye to relieve pressure inside the eyeball. Iridotomy usually is performed in the doctor’s office or in an outpatient facility.
Macular Degeneration [h3]
Macular degeneration is a disease characterized by irreversible deterioration of the light-sensitive cells of the macula—the part of the retina (the light-sensitive membrane lining the back of the eye) that provides sharp focus in the center of the field of vision. The retina transforms light into electrical signals that travel along the optic nerve to the brain, which perceives them as visual images. Sharp central vision allows you to see fine details clearly, which is essential for such everyday activities as reading, driving, and recognizing colors and faces. As you age, the macula can deteriorate. This process can occur rapidly, or it can be slow and progressive. Macular degeneration often affects both eyes, one after the other.
There are two main forms of age-related macular degeneration—dry and wet. About 90 percent of people who have the disease have the dry form, in which the macula breaks down slowly, gradually resulting in blurred central vision. The other 10 percent have the wet form, which progresses more rapidly and carries a greater risk of vision loss. In the wet form, fragile, abnormal blood vessels grow under the retina and bleed and leak fluid, causing internal scarring and formation of a large blind spot in the center of the field of vision. Some hereditary forms of macular degeneration can affect children and adolescents. These forms of the disease are rare and can be referred to collectively as juvenile macular degeneration or dystrophy.
There is no cure for either form of age-related macular degeneration. Although there is currently no proven treatment for dry macular degeneration, this does not mean that you will lose your sight, because the disease progresses very slowly. The doctor may prescribe a supplement containing antioxidants and zinc and recommend changes in your diet that may help protect your eyes from additional damage and help slow the progression of the disease. Eat lots of fruits and vegetables, which are rich in antioxidants. Two antioxidants, lutein and zeaxanthin (which make up the pigment in the macula), are naturally protective of the macula.
Wearing sunglasses that block ultraviolet rays and sun visors may help prevent damage to the macula. Try vision aids such as magnifying glasses, bright lights, large-print reading materials, special lenses, and computer monitors with large print.
Diabetic Retinopathy [h3]
Diabetic retinopathy is an eye disorder in which changes in the blood vessels of the retina (the light-sensitive membrane that lines the back of the eye) can lead to vision loss or blindness. The disorder occurs in people who have diabetes, which can damage blood vessels, including those in the eye.
In some people who develop diabetic retinopathy, the blood vessels in the retina leak fluid. In others, abnormal new blood vessels grow on the surface of the retina and bleed and leak into the vitreous fluid (the substance that makes up the mass of the inside of the eyeball), preventing light from reaching the retina. The abnormal blood vessels also can produce scar tissue that pulls the retina away from the back of the eye, causing retinal detachment.
Anyone who has diabetes can develop diabetic retinopathy, and the longer you have diabetes, the more likely you are to develop this eye disorder. Nearly half of all people who have diabetes develop diabetic retinopathy. Good control of both blood sugar (glucose) levels and blood pressure and early detection and treatment of diabetic retinopathy can help slow progression of the disease and can help prevent vision loss and blindness.
To prevent diabetic retinopathy or to slow its progression, your doctor will recommend controlling the level of glucose in your blood with diet, exercise, and medication (insulin, in some cases). He or she will stress the importance of keeping your blood pressure within the normal range.
In some cases, an ophthalmologist may recommend laser surgery, in which a surgeon directs a highly concentrated beam of light onto the retina either to seal leaking blood vessels or to shrink abnormal blood vessels. The procedure is done using a local anesthetic and can be performed in the doctor’s office or in an outpatient facility; you return home the same day. Laser surgery can reduce the risk of severe vision loss from diabetic retinopathy, but it may not restore vision that has already been lost. After surgery you may lose some peripheral (side) vision, and your color and night vision may also be affected. In some cases, the surgery must be repeated.
For advanced cases of diabetic retinopathy in which leaking blood has filled the vitreous fluid, an ophthalmologist may recommend a type of microsurgery (delicate surgery performed under a microscope) called vitrectomy instead of laser surgery. In vitrectomy, the blood-filled vitreous fluid is removed and replaced with a clear saline (saltwater) solution. Other than improved vision, you will not notice any difference between the saline solution and the vitreous fluid. Vitrectomy may take several hours to complete and is performed in a hospital using either local or general anesthesia. You may need to stay in the hospital overnight. Recovery time varies depending on the extent of the problem.
Retinal Detachment [h3]
Retinal detachment occurs when the retina—the light-sensitive membrane that lines the inside of the back of the eye—lifts away from the choroid, the layer of blood vessels beneath the retina that supplies the eye with oxygen and nutrients. In most cases, detachment occurs after a hole or tear that has formed near the front edge of the retina allows vitreous fluid (the substance that makes up the mass of the inside of the eyeball) to seep between the retina and the choroid, detaching the retina. The hole or tear forms either as a result of degeneration of the retina or because the vitreous fluid has shrunk away from the retina and torn it.
If not treated, this process continues until more and more of the retina lifts away from the choroid. Eventually, the retina is attached only at the front of the eye (to the ciliary body) and at the back of the eye (to the end of the optic nerve). Retinal detachment may affect both eyes, but rarely at the same time.
Retinal detachment is a rare condition, affecting middle-aged and older men and women in equal numbers. People who are nearsighted have an increased risk of retinal detachment because the retina is stretched abnormally by the elongated shape of the eyeball. Other risk factors include eye injury and having a lens removed for treatment of a cataract. If the disorder is left untreated, a person can lose vision in the affected eye.
If an ophthalmologist detects a hole or tear in the retina before detachment begins, he or she may repair the tissue using either cryosurgery (freezing) or laser photocoagulation (in which a highly concentrated beam of light is used to seal or destroy the area around the tear). Both treatments are used to secure the retina to the eye and can be performed using either a sedative or a local anesthetic in a doctor’s office or in an outpatient facility.
If detachment has already begun, an ophthalmologist may recommend a surgical procedure called scleral buckling, in which the fluid between the retina and choroid is drained to allow the retina to fall back into place against the choroid. The hole or tear in the retina is then sealed and a silicone band is sewn around the eye to securely attach the sclera (the white of the eye) to the retina.
In a procedure called pneumatic retinopexy, the doctor injects a small gas bubble into the vitreous fluid to push the retina back against the choroid. These procedures may be done either in a hospital or in an outpatient facility using either local or general anesthesia.
Your vision will probably return to normal if the procedure is performed before detachment has begun or if the detachment is limited to the front edge of the retina. If the detachment is more extensive and your central vision has been affected, your visual field and central vision may be permanently impaired to some extent.
After retinal detachment in one eye, there is a significant risk that the condition will develop in the other eye. For this reason, you should see your ophthalmologist as often as he or she recommends to watch for any weak areas in the retina.
Retinal Artery Occlusion [h3]
The retina (the light-sensitive membrane lining the back of the eye) receives its blood supply from the central retinal artery, a tiny blood vessel that enters the back of the eye through the optic nerve. Sometimes, usually in middle-aged or older people, the central retinal artery or one of its branches becomes blocked, cutting off the blood supply to the retina. The blockage may be caused by a thrombus (blood clot) or by an embolus (a tiny fragment of a blood clot or fatty deposit) that has traveled to the artery from the heart or from a blood vessel elsewhere in the body.
In rare cases, it may be possible to restore some of the lost vision by causing the clot or embolus to move farther along the blood vessel to a position where less of the retina is affected. This may be done by reducing pressure inside the eye, either with medication or by draining excess fluid, within a few hours of the appearance of symptoms.
Retinal Vein Occlusion [h3]
The central retinal vein carries oxygen-depleted blood away from the retina (the light-sensitive membrane lining the back of the eye). In rare cases, usually in middle-aged or older people, the central retinal vein or one of its branches becomes blocked by a thrombus (blood clot), which causes blood to leak from the blocked vessel, blurring vision.
Retinal vein occlusion may occur in chronic glaucoma or with high blood pressure. In rare cases, the disorder results from blood diseases in which the blood is thicker than normal and tends to clot more easily. Effective treatment of an underlying disease or condition, such as high blood pressure, can help prevent retinal vein occlusion.
In some cases, an ophthalmologist may recommend laser surgery (which uses a highly concentrated beam of light) to help close leaking blood vessels.
Choroiditis is inflammation of the choroid, the layer of blood vessels beneath the retina (the light-sensitive membrane lining the back of the eye) that supplies the eye with oxygen and nutrients. In some cases, the retina and the vitreous fluid (the substance that makes up the mass of the inside of the eyeball) also become inflamed. Although the exact cause of the disorder usually cannot be identified, sometimes an infectious agent such as the bacterium that causes tuberculosis is the cause. In some cases, an abnormal immune response mistakenly produces antibodies (infection-fighting proteins) that attack the choroid and sometimes other parts of the eye.
To treat choroiditis, a doctor may prescribe corticosteroid drugs to relieve inflammation and pain and eliminate the blurred vision. If choroiditis is caused by an infection, the doctor may prescribe antibiotics.
Optic Neuritis [h3]
Optic neuritis is inflammation of the optic nerve, which disrupts the flow of signals from the retina to the brain and impairs vision. The condition usually develops between ages 20 and 40. In rare cases, optic neuritis results from an infection in the tissues that surround the optic nerve. Optic neuritis can occur in people who have multiple sclerosis, which affects the nervous system.
In most cases, optic neuritis clears up on its own. Sometimes a doctor prescribes high-dose intravenous corticosteroids to relieve inflammation and pain. Although some impairment of vision may persist, vision usually returns to normal within about 6 weeks. After treatment, optic neuritis may recur in the same eye or in the other eye.
Malignant Melanoma [h3]
Malignant melanoma is a cancer that can affect the eyes as well as the skin, and is the most common type of cancer that occurs inside the eye. Malignant melanoma usually occurs in the choroid (the layer of blood vessels beneath the retina that supplies oxygen and nutrients to the eye) or the ciliary body (the muscles that focus the lens). However, it occasionally develops in the iris (the colored part of the eye).
Malignant melanoma affects only one eye and usually occurs in middle-aged or older people. Most tumors are detected during a routine eye examination by an ophthalmologist (eye MD). Others are brought to the doctor’s attention because of a gradual loss of vision in the affected eye.
Treatment for malignant melanoma may include radiation therapy to destroy the cancer cells or surgical removal of the affected eye (enucleation) to remove the tumor and help prevent the cancer from spreading. Because malignant melanoma can spread, your doctor will continue to monitor your condition after you have been treated.
Retinoblastoma is a rare, malignant tumor of the retina that occurs in one or both eyes, usually in children between ages 2 and 3. Because retinoblastoma is often inherited, you should seek genetic counseling before having children if you know that the disorder runs in your family. If you already have a child, have his or her eyes examined by an ophthalmologist soon after birth, and tell the doctor about your family history of retinoblastoma.
Early detection and treatment with medication, radiation therapy, laser therapy (treatment using a highly concentrated beam of light), or cryotherapy (freezing) can be effective. If the cancer is advanced, the doctor may recommend surgical removal of the eye (enucleation) to remove the tumor and help prevent the cancer from spreading to other parts of the body. After the eye has been removed, the child may need to have radiation therapy and chemotherapy.
Secondary Tumors [h3]
Cancer cells can spread through the bloodstream or the lymphatic system from a tumor in one area of the body to form a tumor in another part of the body, including in the eye.
A secondary tumor is treated separately from a primary tumor. A doctor may prescribe chemotherapy or radiation therapy to block the growth of or destroy a secondary tumor in the eye. Any loss of vision that occurs before treatment may be permanent.
Color Vision Deficiency [h3]
Color vision deficiency (also called color blindness) is a vision disorder in which a person sees colors differently than other people see them or has difficulty distinguishing shades of some colors. The disorder occurs when malfunctioning receptor cells for color in the retina (the light-sensitive membrane lining the back of the eye) transmit incorrect information about color to the brain.
Color vision deficiency is a common disorder that is usually inherited. Although women can carry the gene for the common form of color vision deficiency and pass it on to their children, men are more often affected by the disorder. Difficulty distinguishing colors can develop when normal age-related changes in the lens of the eye cause it to darken, impairing a person’s ability to see differences between some colors. The disorder can also result from a disease or injury that damages the eye or the optic nerve, or from degeneration of the retina or the optic nerve.
Although there is no cure for color vision deficiency, your ophthalmologist can recommend steps you can take to deal with the problem, such as learning to recognize colors by brightness or location. For example, to read traffic signals, you remember that the red light is on the top and the green light is on the bottom. Some people who have difficulty distinguishing shades of red and green may benefit from using tinted prescription glasses.