Retina

Age Related Macular Degeneration (AMD)

Age related macular degeneration (AMD) is one of the most common causes of poor vision after age 60. AMD is a deterioration or breakdown of the macula. The macula is a small area at the center of the retina in the back of the eye that allows us to see fine details clearly and perform activities such as reading and driving.

The visual symptoms of AMD involve loss of central vision. While peripheral (side) vision is unaffected, one loses the sharp, straight-ahead vision necessary for driving, reading, recognizing faces, and looking at detail.

Although the specific cause is unknown, AMD seems to be part of aging. While age is the most significant risk factor for developing AMD, heredity, blue eyes, high blood pressure, cardiovascular disease, and smoking have also been identified as risk factors. AMD accounts for 90 percent of new legal blindness in the US.

Dry Macular Degeneration	Wet Macular Degeneration

Nine out of 10 people who have AMD have the dry form (called atrophic), which results in thinning of the macula. Dry AMD takes many years to develop. Currently there is no treatment for this form of AMD. Certain vitamins are felt to slow progression of the disorder.

The wet form of AMD (called exudative) is less common (occurring in one out of 10 people with AMD), but is more serious. In the wet form of AMD, abnormal blood vessels may grow in a layer beneath the retina, leaking fluid and blood and creating distortion or a large blind spot in the center of your vision. If the blood vessels are not growing directly beneath the macula, laser surgery is the only proven effective treatment, to date, for wet AMD. The procedure usually does not improve vision but prevents further loss of vision. For those wet AMD patients whose blood vessels are growing directly under the center of the macula, a procedure called photodynamic therapy (PDT) may be used to treat some patients with fewer visual side effects than other treatments.

	Promising AMD research is being done on many fronts. In the meantime, high-intensity reading lamps, magnifiers and other low-vision aids help people with AMD make the most of their remaining vision.
An Amsler Grid is used to evaluate whether distortion is present or not. Distortion is a symptom of macular degeneration.

Macular Degeneration and Nutritional Supplements

Age-related macular degeneration (AMD) is a disease caused by damage or breakdown of the macula, the small part of the eye's retina that is responsible for our central vision. This condition affects both distance and close vision and can make some activities-like threading a needle or reading-very difficult or impossible. Macular degeneration is the leading cause of severe vision loss in people over 65.

Although the exact causes of AMD are not fully understood, a recent scientific study shows that antioxidant vitamins and zinc may reduce the impact of AMD in some people with the disease.

Among people at high risk for late-stage macular degeneration (those with intermediate AMD in both eyes or advanced AMD in one eye), a dietary supplement of vitamins C, E and beta carotene, along with zinc, lowered the risk of the disease progressing to advanced stages by about 25 to 30 percent. However, the supplements did not appear to benefit people with minimal AMD or those who have no evidence of macular degeneration.

Light may affect the eye by stimulating oxygen, leading to the production of highly reactive and damaging compounds called free radicals. Antioxidant vitamins (vitamins C and E and beta carotene) may work against this activated oxygen and help slow progress of macular degeneration.

Zinc, one of the most common minerals in our body, is very concentrated in the eye, particularly in the retina and macula. Zinc is necessary for the action of over 100 enzymes, including chemical reactions in the retina. Studies show some older people have low levels of zinc in their blood. Because zinc is important for the health of the macula, supplements of zinc in the diet may slow down the process of macular degeneration.

The levels of antioxidants and zinc that were shown to be effective in slowing AMD's progression cannot be consumed through your diet alone. These vitamins and minerals are recommended in specific daily amounts as supplements to a healthy, balanced diet.

It is very important to remember that vitamin supplements are not a cure for AMD, nor will they restore vision you may have already lost from the disease. However, specific amounts of certain supplements do play a key role in helping some people at high risk for advanced AMD to maintain their vision. You should speak with your optometrist or ophthalmologist to determine if you are at risk for developing advanced AMD, and to learn if supplements are recommended for you.

Macular Edema

Macular edema is swelling of the macula, the small area of the retina responsible for central vision. The edema is caused by fluid leaking from retinal blood vessels. Central vision, used for reading and other close detail work, is affected.

Because the macula is surrounded by many tiny blood vessels, anything affecting them, such as a medical condition affecting blood vessels elsewhere in the body or an abnormal condition originating in the eye, can cause macular edema.

Retinal blood vessel obstruction, diabetes, eye inflammation, and age-related macular degeneration have all been associated with macular edema. The macula may also be affected by swelling following cataract extraction, though typically this resolves itself naturally.

Treatment seeks to remedy the underlying cause of the edema. Eyedrops, injections of cortisone around the eye or laser surgery can be used to treat macular edema. Recovery depends on the severity of the condition causing the edema.

Lattice Degeneration

Lattice degeneration is thinning and weakening of the retina, the light-sensitive layer of cells lining the back of the eye, that can lead to a retinal tear.

The vitreous, a clear gel-like substance that fills the inside of the eye, is contained in a sac loosely attached to the retina. As one ages, the vitreous takes on a more fluid consistency and the sac sometimes separates from the retina. In lattice degeneration, there are places where the sac is strongly attached to the retina and pulls on it. This pulling weakens the retina and creates lattice lesions that look like white crisscrossing lines on the retina.

If part of the vitreous sac becomes detached from the retina, the friction and pulling where it is still attached can create a tear in the retina. Lattice degeneration can sometimes cause retinal detachments when holes or tears in the lattice formation permit vitreous fluid to get under the retina.

Fortunately, most people with lattice degeneration do not develop a retinal detachment. Preventive treatment of lattice degeneration has not been shown to prevent retinal detachment, but lattice degeneration should be monitored. If you have a history of lattice degeneration, you should be aware of the symptoms of retinal tears and detachment.

Ocular Histoplasmosis Syndrome (OHS)

OHS is a major cause of visual impairment in the eastern and central United States where 90 percent of adults have been exposed to histoplasma capsulatum. This common fungus is found in molds from soil enriched with bat, chicken or starling droppings and yeasts from animals.

Although the fungus is not found directly in the eye, people with OHS usually test positive for previous exposure to histoplasma capsulatum.

Histoplasmosis is usually mistaken for a cold. The symptoms are very similar. The body's immune system normally overcomes the infection in a few days. The only evidence of histoplasmosis is histo spots, tiny scars on the retina. Generally histo spots do not affect vision, but for unknown reasons, some people can have ocular complications years or decades later.

Doctors believe that the histoplasmosis spores travel from the lungs to the eye where they settle in the choroid, the layer of tiny blood vessels that provides blood and nutrients to the retina, the light-sensing layer of cells lining the back of the eye.

Ocular histoplasmosis develops when fragile, abnormal blood vessels grow under the retina. The 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 only proven treatment for OHS is a form of laser surgery called photocoagulation. The laser's small, powerful beam of light destroys the abnormal blood vessels, as well as a small amount of the retinal tissue. Treatment is not necessary unless the new vessels are in the macula, the part of the retina responsible for acute central vision.

Although only a tiny fraction of people infected with the histoplasmosis virus develop OHS, if you have been exposed to histoplasmosis you should be sensitive to any changes in your eyesight.

Proliferative Diabetic Retinopathy (PDR)

Proliferative diabetic retinopathy is a complication of diabetes caused by changes in the blood vessels of the eye. If you have diabetes, your body does not use and store sugar properly. High blood sugar levels create changes in the veins, arteries and capillaries that carry blood throughout the body. This includes the tiny blood vessels in the retina, the light-sensitive nerve layer that lines the back of the eye.

In PDR, the retinal blood vessels are so damaged they close off. In response, the retina grows new, fragile blood vessels. Unfortunately, these new blood vessels are abnormal and grow on the surface of the retina, so they do not resupply the retina with blood.

Occasionally, these new blood vessels leak and cause a vitreous hemorrhage. Blood in the vitreous, the clear gel-like substance that fills the inside of the eye, blocks light rays from reaching the retina. A small amount of blood will cause dark floaters, while a large hemorrhage might block all vision, leaving only light and dark perception.

The new blood vessels can also cause scar tissue to grow. The scar tissue shrinks, wrinkling and pulling on the retina and distorting vision. If the pulling is severe, the macula may detach from its normal position and cause vision loss.

Laser surgery may be used to shrink the abnormal blood vessels and reduce the risk of bleeding. The body will usually absorb blood from a vitreous hemorrhage, but that can take days, months or even years. If the vitreous hemorrhage does not clear within a reasonable time, or if a retinal detachment is detected, an operation called a vitrectomy can be performed. During a vitrectomy, the eye surgeon removes the hemorrhage and the abnormal blood vessels that caused the bleeding.

People with PDR sometimes have no symptoms until it is too late to treat them. The retina may be badly injured before there is any change in vision. There is considerable evidence to suggest that rigorous control of blood sugar decreases the chance of developing serious proliferative diabetic retinopathy.

Because PDR often has no symptoms, if you have any form of diabetes you should have your eyes examined regularly by an ophthalmologist.

Retinitis Pigmentosa (RP)

TUNNEL VISION
Retinitis pigmentosa (RP) describes a group of related diseases that tend to run in families and cause a slow but progressive loss of vision. RP affects the rods and cones of the retina, the light-sensitive nerve layer at the back of the eye, and results in a decline in vision in both eyes. RP usually affects both eyes equally with severity ranging from no visual problems in some families to blindness at birth in others. RP gets its name from the fact that one of the symptoms is a clumping of the retinal pigment that can be seen during an eye exam.

The earliest symptom of retinitis pigmentosa, usually noticed in childhood, is night blindness or difficulty with night vision. People with normal vision adjust to the dark quickly, but people with night blindness adjust very slowly or not at all. A loss of side vision, or tunnel vision, is also common as RP progresses. Unfortunately, the combination of night blindness and the loss of peripheral vision can be severe and lead to legal blindness in many people.

While there is a pattern of inheritance for RP, 40% of RP patients have no known previous family history. Learning more about RP in your family can help you and your eye doctor predict how RP will affect you.

Usher's syndrome, in which a person is both deaf and blind, can be associated with RP. The incidence of Usher's syndrome is difficult to determine but surveys of patients suggest up to 10% of RP patients are deaf. The incidence of Usher's syndrome is three cases per 100,000. It is the most frequent cause of combined deaf-blindness in adults.

Considerable research is being done to find the hereditary cause of RP. As hereditary defects are discovered it may be possible to develop treatments to prevent progression of the disease. While developments are on the horizon, particularly in the area of genetic research, there is currently no cure for retinitis pigmentosa.

Nutritional supplements may have an effect on RP. It has been reported that Vitamin A can slow the progression of RP. Large doses of Vitamin A are harmful to the body and supplements of Vitamin E alone may make RP worse. Vitamin E is not harmful if taken with Vitamin A or in the presence of a normal diet. Your ophthalmologist or optometrist can advise you about the risks and benefits of Vitamin A and how much you can safely take.

Despite visual impairment, people with RP can maintain active and rewarding lives through the wide variety of rehabilitative services that are available today. Until there is a cure, periodic examinations by your ophthalmologist or optometrist will keep you informed of legitimate scientific discoveries as they develop.

Floaters and Flashes

Small specks or clouds moving in your field of vision as you look at a blank wall or a clear blue sky are known as floaters. Most people have some floaters normally but do not notice them until they become numerous or more prominent.

In most cases, floaters are part of the natural aging process. Floaters look like cobwebs, squiggly lines or floating bugs, and appear to be in front of the eye, but are actually floating inside. As we get older, the vitreous-the clear gel-like substance that fills the inside of the eye-tends to shrink slightly and detach from the retina, forming clumps within the eye. What you see are the shadows these clumps cast on the retina, the light-sensitive nerve layer lining the back of the eye.

The appearance of flashing lights comes from the traction of the vitreous gel on the retina at the time of vitreous separation. Flashes look like twinkles or lightning streaks. You may have experienced the same sensation if you have ever been hit in the eye and seen stars.

Floaters can get in the way of clear vision, often when reading. Try looking up and then down to move the floaters out of the way. While some floaters may remain, many of them will fade over time.

Floaters and flashes are sometimes associated with retinal tears. When the vitreous shrinks it can pull on the retina and cause a tear. A torn retina is a serious problem. It can lead to a retinal detachment and blindness. If new floaters appear suddenly or you see sudden flashes of light, see an ophthalmologist or optometrist immediately.

Detached and Torn Retina

RETINAL DETACHMENT

A retinal detachment is a very serious problem that almost always causes blindness unless treated. The appearance of flashing lights, floating objects, or a gray curtain moving across the field of vision are all indications of a retinal detachment. If any of these occur, see an ophthalmologist or optometrist right away.

As one gets older, the vitreous, the clear gel-like substance that fills the inside of the eye, tends to shrink slightly and take on a more watery consistency. Sometimes as the vitreous shrinks it exerts enough force on the retina to make it tear.

Retinal tears increase the chance of developing a retinal detachment. Fluid vitreous, passing through the tear, lifts the retina off the back of the eye like wallpaper peeling off a wall. Laser surgery or cryotherapy (freezing) are often used to seal retinal tears and prevent detachment.

If the retina is detached, it must be reattached before sealing the retinal tear. There are three ways to repair retinal detachments. Pneumatic retinopexy involves injecting a special gas bubble into the eye that pushes on the retina to seal the tear. The scleral buckle procedure requires the fluid to be drained from under the retina before a flexible piece of silicone is sewn on the outer eye wall to give support to the tear while it heals. Vitrectomy surgery removes the vitreous gel from the eye, replacing it with a gas bubble, which is slowly replaced by the body's fluids.

Branch Retinal Artery Occlusion (BRAO)

Most people know high blood pressure and other vascular diseases pose risks to overall health, but many may not know that high blood pressure can affect vision by damaging arteries in the eye.

Branch retinal artery occlusion (BRAO) blocks the small arteries in the retina, the light- sensing nerve layer lining the back of the eye. The most common cause of BRAO is a thrombosis, the formation of a blood clot. Sometimes the blockage is caused by an embolus, a clot carried by the blood from another part of the body.

Central vision is lost suddenly if the blocked retinal artery is one that nourishes the macula, the part of the retina responsible for fine sharp vision. Following BRAO, vision can range from normal (20/20) to barely detecting hand movement.

BRAO poses significant risks to vision. If you have had a branch retinal artery occlusion or have high blood pressure, regular visits to your ophthalmologist or optometrist are essential.

Branch Retinal Vein Occlusion (BRVO)

Most people know high blood pressure and other vascular diseases pose risks to overall health, but many may not know that high blood pressure can affect vision by damaging veins in the eye. High blood pressure is the most common condition associated with BRVO. About 10 to 12 percent of the people who have BRVO also have glaucoma (high pressure in the eye).

Branch retinal vein occlusion blocks small veins in the retina, the layer of light-sensing cells at the back of the eye. If the blocked retinal veins are ones that nourish the macula, the part of the retina responsible for straight-ahead vision, some central vision is lost. During the course of vein occlusion, sixty percent or greater will have swelling of the central macular vision area. In about one third of people, this macular edema will remain for over one year.

BRVO causes a painless decrease in vision, resulting in misty or distorted vision. If the veins cover a large area, new abnormal vessels may grow on the retinal surface, which can bleed into the eye and cause blurred vision.

There is no cure for BRVO. Finding out what caused the blockage is the first step in treatment. Your ophthalmologist may recommend a period of observation, since hemorrhages and excess fluid may subside on their own. Depending on how damaged the veins are, laser surgery may help reduce the swelling and improve vision. Laser surgery may also shrink the abnormal new blood vessels that are at risk of bleeding.

If you have had a branch retinal vein occlusion, regular visits to your ophthalmologist or optometrist are essential to protect vision.

Central Retinal Artery Occlusion (CRAO)

You probably know high blood pressure and other vascular diseases pose risks to your overall health, but you may not know that they can affect your eyesight by damaging the arteries in your eye.

CRAO usually occurs in people between the ages of 50 and 70. The most common medical problem associated with CRAO is arteriosclerosis, hardening of the arteries. Carotid artery disease is found in almost half the people with CRAO.

The most common cause of CRAO is a thrombosis, an abnormal blood clot formation. Sometimes CRAO is caused by an embolus, a clot that breaks off from another area of the body and is carried to the retina by the bloodstream.

Central retinal artery occlusion (CRAO) blocks the central artery in your retina, the light-sensitive nerve layer at the back of the eye. The first sign of CRAO is a sudden and painless loss of vision that leaves you barely able to count fingers or determine light from dark.

Loss of vision can be permanent without immediate treatment. Irreversible retinal damage occurs after 90 minutes, but even 24 hours after symptoms begin, vision may still be saved. The goal of emergency treatment is to restore retinal blood flow. After emergency treatment, you should have a thorough medical evaluation.

Central Retinal Vein Occlusion (CRVO)

You probably know high blood pressure and other vascular diseases pose risks to overall health, but you may not know that they can affect eyesight by damaging the veins in the eye.

Central retinal vein occlusion (CRVO) blocks the main vein in the retina, the light-sensitive nerve layer at the back of the eye. The blockage causes the walls of the vein to leak blood and excess fluid into the retina. When this fluid collects in the macula-the area of the retina responsible for central vision-vision becomes blurry.

Floaters in your vision are another symptom of CRVO. When retinal blood vessels are not working properly, the retina grows new fragile vessels that leak blood into the vitreous, the fluid that fills the center of the eye. Blood in the vitreous clumps and is seen as tiny dark spots, or floaters, in the field of vision.

In severe cases of CRVO, the blocked vein causes painful pressure in the eye. Retinal vein occlusions commonly occur with glaucoma, diabetes, age-related vascular disease, high blood pressure, and blood disorders.

The first step is finding what is causing the vein blockage. There is no cure for CRVO. Your ophthalmologist may recommend a period of observation, since hemorrhages and excess fluid often subside on their own. Laser surgery may be effective in preventing further bleeding into the vitreous, or for treating glaucoma, but it cannot remove a hemorrhage or cure glaucoma once it is present.

Central Serous Retinopathy (CSR)

Central serous retinopathy is a small, round, shallow swelling that develops on the retina, the light sensitive nerve layer that lines the back of the eye. Although the swelling reduces or distorts vision, the effects are usually temporary. Vision generally recovers on its own within a few months.

In the initial stages of CSR, vision may suddenly become blurred and dim. If the macula-the area of the retina responsible for acute central vision-is not affected, there may be no obvious symptoms.

CSR typically affects adults between the ages of 20 to 50. People with CSR often lose their retinal swelling without treatment, and recover their original vision within six months of the onset of symptoms. Some people with frequent episodes may have some permanent vision loss. Recurrences are common and can affect 20 to 50 percent of people with CSR. While the cause of CSR is unknown, it seems to occur at times of major personal or work related stress.

As CSR usually resolves on its own, no treatment may be necessary. Sometimes laser surgery can reduce the swelling sooner but there is no evidence this improves the final visual outcome. If retinal swelling persists for over three to four months or if an examination reveals early retinal degeneration, laser surgery may be helpful.

Fluorescein Angiography

Fluorescein angiography, a clinical test to look at blood circulation inside the back of the eye, aids in the diagnosis of retinal conditions associated with diabetes, age-related macular degeneration, and other eye abnormalities. The test can also help follow the course of a disease and monitor its treatment. It may be repeated on multiple occasions with no harm to the eye or body.

Fluorescein, a harmless orange-red dye, is injected into a vein in the arm. The dye travels through the body to the blood vessels in the retina, the light-sensitive nerve layer at the back of the eye. A special camera with a green filter flashes a blue light into the eye and takes multiple photographs of the retina. The technique uses regular photographic film. No X-rays are involved.

If there are abnormal blood vessels, the dye leaks into the retina or stains the blood vessels. Damage to the lining of the retina or atypical new blood vessels may be revealed as well. These abnormalities are determined through a careful interpretation of the photographs by an ophthalmologist.

The dye can discolor skin and urine until it is removed from the body by the kidneys. There is little risk in having fluorescein angiography, though some people may have mild allergic reactions to the dye. Severe allergic reactions have been reported but very rarely. Being allergic to X-ray dyes with iodine does not mean you'll be allergic to fluorescein. Occasionally, some of the dye leaks out of the vein at the injection site, causing a slight burning sensation that usually goes away quickly.