Vision with macular degeneration
Macular degeneration, or age-related macular degeneration (AMD) is the leading cause of central vision loss in the Western world in persons over the age of 55. There are currently 15 million people in the United States with AMD and the incidence will increase to 25 million over the next 20 years as our population ages. AMD is therefore a growing public health issue.
Macular degeneration is caused by the deterioration of the central portion of the retina, the inside back layer of the eye that records the images we see and sends them via the optic nerve from the eye to the brain. The retina's central portion, known as the macula, is responsible for focusing central vision in the eye, and it controls our ability to read, drive a car, recognize faces or colors, and see objects in fine detail.
There are two forms of macular degeneration:
The Dry Type.
This is the most common form. In this type of macular degeneration, the delicate tissues of the macula become thinned and cease to function properly.
The Wet Type.
This is less common, but is typically more damaging. The wet type of macular degeneration is caused by the growth of abnormal blood vessels behind the macula. The abnormal blood vessels tend to hemorrhage or leak, with the result being the formation of scar tissue if left untreated. In some instances, the dry type of macular degeneration can turn into the wet type.
Dry Macular Degeneration (non-neovascular).
"Dry" Macular Degeneration
Waste products build up under the retina. Vision loss is gradual
Dry AMD is an early stage of the disease, and may result from the aging and thinning of macular tissues, depositing of pigment in the macula, or a combination of the two processes.
Dry macular degeneration is diagnosed when yellowish spots known as drusen begin to accumulate from deposits or debris from deteriorating tissue primarily in the area of the macula. Gradual central vision loss may occur with dry macular degeneration but is not nearly as severe as symptoms associated with the wet form of AMD.
No FDA-approved treatments are available for the dry form of macular degeneration. A large, well-designed study (age-related eye disease) has concluded that high levels of dietary supplements consisting of a combination of vitamin C, vitamin E, beta carotene and zinc at specific concentrations may lower the risk of developing advanced stages of macular degeneration by 25% for people at high risk.
Wet Macular Degeneration (neovascular).
"Wet" Macular Degeneration
Leaking blood vessels cause fluids build-up, detaching cone and pigment cells. Vision loss can be sudden.
In about 10 percent of cases, dry AMD progresses to a more advanced and damaging form of the eye disease known as wet macular degeneration. With wet AMD, new blood vessels grow (neovascularization) beneath the retina and leak blood and fluid. This leakage causes permanent damage to light-sensitive retinal cells, which die off and create blind spots in central vision.
Neovascularization, the underlying process causing wet AMD and abnormal blood vessel growth, is the body's misguided way of attempting to create a new network of blood vessels to supply more nutrients and oxygen to the eye's retina. But the process instead creates scarring, leading to sometimes severe central vision loss.
Wet forms of macular degeneration are further classified into two general types:
Classic: When blood vessel growth and scarring has very clear, delineated outlines observed beneath the retina, this type of wet AMD is known as classic choroidal neovascularization (CNV) usually associated with more severe vision loss.
Occult: New blood vessel growth beneath the retina is not as pronounced and leakage is less evident in the occult CNV form of wet macular degeneration, which typically produces less severe vision loss.
Symptoms and Signs
Macular degeneration develops differently in each person. Because it will affect different regions of the macula from person to person, the symptoms tend to vary. Macular degeneration causes a progressive loss of central sight, however, it does not cause total blindness. Peripheral vision is unaffected allowing a certain amount of mobility in normal surroundings. If left untreated, the wet type of macular degeneration may progress rapidly.
Symptoms often associated with macular degeneration include:
- A gradual loss of ability to see objects clearly
- A gradual loss of clear correct colors
- Vision that is noticeably distorted
- Strait lines appear wavy
- A dark or empty area appearing in the center of vision
- Difficulty reading or seeing objects up close
- Objects may appear the wrong shape or size
The symptoms described above may not necessarily mean that you have macular degeneration. However, if you experience one or more of these symptoms, contact your eye doctor for a complete exam
Viewing a chart of black lines arranged in a graph pattern (Amsler grid) is one way to tell if you are having these vision problems.
Testing Your Vision with the Amsler Grid
You can check your vision daily by using an Amsler grid like the one pictured below. You may find changes in your vision that you wouldn't notice otherwise. Putting the grid on the front of your refrigerator is a good way to remember to look at it each day.
To use the grid: (click here for a printable copy)
1. Wear your reading glasses and hold this grid at 12-15 inches in good light.
2. Cover one eye.
3. Look directly at the center dot with uncovered eye.
4. While looking directly at the center dot, note whether all lines of the grid are straight or if any areas are distorted, blurred or dark.
5. Repeat this procedure with the other eye.
6. If any area of the grid looks wavy, blurred or dark, contact the Coastal Eye physicians immediately.
Treatments for Macular Degeneration
Careful monitoring of vision and regular eye exams are important for those with both forms of ARMD. Dietary modifications are also important to help prevent the dry form of the disease from worsening.
Dr. McMullen treating wet ARMD with Lucentis® in one of his patients.
A new class of drugs, known as anti-VEGF medications, have been shown to slow and even reverse the progression of the disease in some patients. This form of therapy is designed to inhibit the unwanted blood vessel growth caused by ARMD, thereby reducing leakage and bleeding. Examples of new therapies that we now offer include Avastin®, Lucentis® and Macugen®.
Another treatment for wet ARMD is Photodynamic Therapy (PDT), a laser treatment that uses a light-activated drug called Visudyne. The drug is injected into an arm vein and travels through the bloodstream to the retina, where it is activated by a non-thermal laser. A clot is formed, closing the leaking blood vessels with minimal scarring to the retina.
Previous laser treatments for wet ARMD were successful in preventing loss of vision, but caused scarring and damage to the retinal tissue. PDT allows the laser beam to focus on the area where the drug has concentrated and very quickly treat it, eliminating the likelihood of damage. The treatment may be reapplied if necessary.