Age-related Macular Degeneration
Age-related macular degeneration (AMD) is a disease that blurs the sharp, central vision you need for “straight ahead” activities such as reading, sewing , and driving. AMD affects the macula, the part of the eye that allows you to see fine detail.
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.
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 considered to be advanced AMD and is more severe than the dry form. An early symptom of wet AMD is that straight lines appear wavy.
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 in the affected eye can be lost gradually.
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.
Dry AMD has three stages, all of which occur in one or both eyes:
- Early AMD. People with early AMD have either several small drusen or a few medium-sized drusen. At this stage, there are no symptoms and no vision loss.
- Intermediate AMD. People with intermediate AMD have either many medium-sized drusen or one or more large drusen. Some people see a blurred spot in the center of their vision. More light may be needed for reading and other tasks.
- Advanced Dry AMD. In addition to drusen people with advanced dry AMD have a breakdown of light-sensitive cells and supporting tissue in the central retinal area. This breakdown can cause a blurred spot in the center of your vision. Over time, the blurred spot may get bigger and darker, taking more of your central vision. You may have difficulty reading or recognizing faces until they are very close to you.
If you have vision loss from dry AMD in one eye only, you may not notice any changes in your overall vision. With the other eye seeing clearly, you can still drive, read, and see fine details. You may notice changes in your vision only if AMD affects both eyes.
A cataract is a clouding of the lens of the eye. The lens is a clear oval structure with three layers: the nucleus, the cortex, and the capsule. It may help to think of the lens structure as a peach, where the nucleus is the peach pit, the cortex is the flesh of the peach surrounding the pit, and capsule is the peach skin, or elastic covering of the lens. You have a cataract when the nucleus becomes opaque (that is, it is no longer clear) or when small opacities develop in the cortex that block or scatter light.
There are three types of cataracts that affect different parts of the lens, have different symptoms and cause different vision problems.
Nuclear cataract is the most common type of cataract, and is related to the aging process. The nucleus gradually hardens and becomes opaque, causing difficulty identifying colors and seeing at a distance.
Cortical cataract is the next most common type, often affecting people who have diabetes. Web-shaped opacities develop in the cortex, interfering with the passage of light. This can result in problems with glare and loss of contrast, as well as difficulty with distance and near vision.
Subcapsular cataract develops under the back of the capsule or elastic covering of the lens and is common in people with diabetes or high myopia, adults with retinitis pigmentosa, and in people taking cortisone. This type of cataract can cause glare sensitivity and blur.
In the early stages, only a doctor can detect a cataract because there may not be any symptoms. When you do start to notice changes in vision, they may include:
- blurry distance vision, especially outdoors; streaks or rays of light seeming to come from headlights and stop signs
- instinctively shading your eyes from the sun or feeling more comfortable wearing a visor
- print appearing faded and lacking in contrast
- colors appearing faded or changed in hue. Blue may appear to be green and yellow may look white.
Because these may also be symptoms of other eye conditions, it is important to see your eye doctor annually, or when you notice a persistent change in vision.
Cataracts are treated with surgery. Cataract surgery is an outpatient procedure performed by an ophthalmologist. Surgery can often be postponed until the cataract begins to seriously affect your ability to function. There is no medicine or other treatment that can dissolve or remove cataracts.
Diabetic Retinopothy is an eye disease caused by complications of diabetes. Diabetes causes damage to the blood vessels that nourish the retina, the seeing part at the back of the eye.
In people with diabetes the retinal blood vessels may expand and leak fluid, abnormal new blood vessels may grow, blood vessels may break and cause bleeding. These changes may result in visual loss or blindness.
Every person with diabetes is at risk of developing diabetic retinopothy. The longer a person has diabetes the more likely the person is to develop diabetic retinopothy. Regular eye exams when first diagnosed with diabetes and then at least every two years will reduce your risk of vision loss and blindness.
There are no symptoms in the early stages of diabetic retinopothy. Vision may not change until the disease is advanced. Vision loss due to diabetic retinopothy can be prevented if detected and treated early. Tight control of your diabetes will delay the development of retinopothy.
Glaucoma is a group of eye diseases that gradually steals sight without warning and often without symptoms. Vision loss is caused by damage to the optic nerve. The nerve acts like an electric cable with over a million wires and is responsible for carrying the images we see to the brain.
The two main types of glaucoma are open angle glaucoma and angle closure glaucoma.
Primary Open Angle Glaucoma
This is the most common form of glaucoma, affecting about three million Americans. It happens when the eye’s drainage canals become clogged over time. The inner eye pressure (also called intra ocular pressure or IOP) rises because the correct amount of fluid can’t drain out of the eye. With open angle glaucoma, the entrances to the drainage canals are clear and should be working correctly. The clogging problem occurs inside the drainage canals, like the clogging that can occur inside the pipe below the drain in a sink.
Most people have no symptoms and no early warning signs. If open angle glaucoma is not diagnosed and treated it can cause a gradual loss of vision. This type of glaucoma develops slowly and sometimes without noticeable sight loss for many years. It usually respond well to medication, especially if caught early and treated.
Angle Closure Glaucoma
This type of glaucoma is also known as acute glaucoma or narrow angle glaucoma. It is much more rare and is very different from open angle glaucoma in that the eye pressure usually goes up very fast. This happens when the drainage canals get blocked or covered over, like the clog in a sink when something is covering the drain. With angle closure glaucoma, the iris and cornea is not as wide and open as it should be. The outer edge of the iris bunches up over the drainage canals when the pupil enlarges too much or too quickly. This can happen when entering a dark room.
A simple test can be used to see if your angle is normal and wide or abnormal and narrow. Treatment of angle closure glaucoma usually involves surgery to remove a small portion of the outer edge of the iris. This helps unblock the drainage canals so that the extra fluid can drain. Usually surgery is successful and long lasting. However, you should still receive regular check-ups. Symptoms of angle closure glaucoma may include headaches, eye pain, nausea, rainbows around lights at night, and very blurred vision.
Glaucoma can occur as the result of an eye injury, inflammation, tumor or in advanced cases of cataract or diabetes. It can also be caused by certain drugs such as steroids. This form of glaucoma may be mild or severe. The type of treatment will depend on whether it is open angle or angle closure glaucoma.
Normal Tension Glaucoma (NTG)
Normal tension glaucoma is also known as low tension glaucoma or normal pressure glaucoma. In this type of glaucoma, the optic nerve is damaged even though intraocular pressure (IOP) is not very high.
Those at higher risk for this form of glaucoma are people with a family history of normal tension glaucoma, people of Japanese ancestry, and people with a history of systemic heart disease, such as irregular heart rhythm. Normal tension glaucoma is usually detected after an examination of the optic nerve.
This is a form of secondary open angle glaucoma. It occurs when the pigment granules in the back of the iris (the colored part of the eye) break into the clear fluid produced inside the eye. These tiny pigment granules flow toward the drainage canals in the eye and slowly clog them, causing eye
pressure to rise. Treatment usually includes medication or surgery.
Retinitis Pigmentosa is an eye disease that affects a person’s night vision and peripheral vision. It is a genetic disorder that is usually hereditary. Symptoms start with decreased night vision and later progresses to a diminishing of peripheral vision. The rate of decline varies depending on the genetic makeup of the disorder and also varies somewhat in individuals.
Usher Syndrome affects the eyesight in a manner similar to retinitis Pigmentosa but also affects the hearing.
Stargardt disease is the most common form of inherited juvenile macular degeneration. It is characterized by the reduction of central vision with a reservation of peripheral (side) vision.
Stargardt disease is usually diagnosed in individuals under the age of 20 when decreased central vision is first noticed. On examination, the retina of an affected individual shows a macular lesion surrounded by yellow-white flecks, or spots, with irregular shapes.
The progression of visual loss is variable. Eventually, almost all with Stargardt disease are expected to have visual acuities in the range of 20/200 to 20/400. The reduced visual acuity due to Stargardt disease cannot be corrected with prescription eyeglasses or contact lenses. In late stages of the disease, there may also be noticeable impairment of color vision.
Stargardt disease is almost always inherited as an autosomal recessive disorder. It is inherited when both parents, called carriers, have one gene for the disease paired with one normal gene. Each of their children has a 25% chance of inheriting the two copies of the Stargardt gene (one from each parent) need to cause the disease. Carriers are unaffected because they have only one copy of the gene.
Although there is currently no treatment of Stargardt disease, individuals may benefit from the use of low vision aids and orientation and mobility training.