Overview
Have you recently discovered that you or a family member has age-related macular degeneration (AMD)? What does it mean to be diagnosed with this condition? What can you, family members, doctors, or other health care professionals do about it? And how does a person with limited vision continue activities such as reading, writing, watching TV, dining out, traveling, or even using a computer?
If you have not yet found answers to these and other questions, you are not alone. Many people who have been diagnosed with AMD, or have family members with AMD, feel they lack specific information about it. You may be anxious and fearful of the future. The goal of this course is to provide AMD-related information that enables you to take an active role in the rehabilitation process.
The course is divided into five lessons. Lesson 1 compares healthy eyesight to the symptoms and progression of AMD. It also identifies risk factors. Lesson 2 explains the process of diagnosing the disease and the doctor-patient relationship. Lesson 3 provides information about how to maximize vision. Lesson 4 suggests ways to continue accustomed activities. Lesson 5 discusses the emotional impact of AMD. A resource list includes sources of further information, vision aids, and reading materials. A supplement describes current treatments and research.
You do not need any prerequisites to begin this course. You do need the materials that The Hadley School for the Blind has provided and writing materials in the medium of your choice. If you are taking the audio version of the course, you need your own tape recorder.
The reviews that follow each section are for your personal development only. Use them as comprehension checks by comparing your responses to the ones provided. Do not send your responses to your Hadley instructor. You can always contact your instructor, however, to clarify concepts or discuss your answers. To do so, refer to the contact information card that is included with your course materials.
To complete the course, you are required to submit five assignments, one at the end of each lesson. These assignments enable your instructor to assess your mastery of the material in the lessons. You can mail, fax, or email your assignments to your instructor. If mailing them, use the enclosed labels. The enclosed contact card lists your instructor’s fax number and email address. Students who are eligible to mail materials as Free Matter for the Blind may do so provided the materials are in large print or on cassette or computer disk. The minimum size for large print is 14-point type.
Now, if you are ready to learn about AMD, proceed to Lesson 1: Recognizing AMD.
Overview1
Lesson 1: Recognizing AMD
What does it mean to have AMD? What might put a person at risk for developing AMD? This lesson describes how a healthy eye works, how AMD affects the eye and vision, and some risk factors. Recognizing AMD will enable you to take an active role in the rehabilitation process.
Objectives
After completing this lesson, you will be able to
a.describe how a healthy retina works
b.describe the progression of AMD
c.discuss the risk factors for developing AMD
Key Terms
The following terms appear in this lesson. Familiarize yourself with their meanings so you can use them in your course work.
AMD or ARMD:stands for age-related macular degeneration
Bruch’s
membrane:the layer that separates the retinal pigment epithelium (RPE) from the choroid (blood vessel layer)
choroid:a layer that contains blood vessels behind the retina
cones:photoreceptor cells that enable detailed, sharp, central vision, and color vision
cornea:the transparent part of the front of the eyeball that admits light into the interior
drusen:round, yellow-white deposits, typically found in the macula of an eye that has macular degeneration
exudate:fluid that passes through vessels’ walls into tissues
fovea:the center of the macula, densely packed with cones
hyperopia:farsightedness; vision is better for distant objects than for near ones
iris:a thin circle of membrane in the front of the eye that gives the eye its color
lens
(of the eye):transparent, elastic tissue that helps bring rays of light to focus on the retina
macula:the center of the retina, which contains mostly cones and is responsible for clear central vision
presbyopia:aging of the eyes, which results in the loss of ability to focus near objects
pupil:a small opening in the center of the iris that allows light to pass into the eye
retina:the lining of the back of the eye that receives the visual image and transmits the information to the brain for interpretation
retinal pigment
epithelium:a supporting layer of cells under the retina that delivers oxygen to and receives waste products from the cones and rods
rods:photoreceptors that are responsible for perceiving light and dark as well as for detecting movement and large general shapes; rods are used mostly in peripheral vision; they do not provide color
The Healthy Retina
This section describes some parts of the eye that are related to the disease known as AMD. It is not, however, a thorough presentation of the physiology and anatomy of the human eye. Such a description is beyond the scope of this course. For more information about the human eye, refer to the Resource List and the Hadley Course Catalog.
A healthy eye “sees” when rays of light enter through the cornea at the front of the eye, pass through the pupil and the lens, and fall onto the retina, which lines the inside back surface of the eyeball. The image on the retina is then changed into electrical information that is sent via the optic nerve to the brain, where it is interpreted. Seeing is actually an interpretation of light stimulation. The following diagram is a simplified drawing of the human eye.
The retina contains rods and cones, whose purpose is to convert the information into electrical pulses for transmission to the brain. They are photoreceptor cells, which are special types of nerve cells. The word photoreceptor means “light receiving.”
Rods outnumber cones by about 20 to 1. The rods are sensitive enough to detect very small amounts of light. Therefore, they enable people to see in dim lighting and to detect movement. The rods are not very sensitive to color because they absorb only a small amount of light. Rods are located mostly in the sides of the retina, so they enable people to see things in their peripheral, or side, vision.
The cones are concentrated in a central part of the retina called the macula.The cones are very sensitive to color, and they are responsible for the ability to see sharp, detailed images. The fovea is an area the size of a pinhead in the very center of the macula. This part is densely packed with cones. The fovea is therefore responsible for the sharpest vision. In a healthy eye, the rods and cones enable a person to see in both dim and bright light. Together they are responsible for the ability to perceive both general shapes and sharp, colored detail.
All the cells of the body need nourishment and produce waste. The photoreceptor cells are no exception. The part that delivers oxygen to and receives waste from the rods and cones is called the retinal pigment epithelium(RPE). A layer called the choroidcontains the blood vessels that transport the nutrients and remove the waste. Between the choroid and the RPE is a layer called Bruch’s membrane. It chemically separates and protects the delicate layers of the RPE and the photoreceptor cells. The following diagram illustrates some of the layers found in the retina.
Section Review
Review the information in this sectionby answering the following questions. A suggested response follows each item.
1.How does a healthy eye “see”?
Light enters through the cornea, passes through the pupil and lens, and falls onto the retina. The image on the retina is then changed into electrical information that is sent by way of the optic nerve to the brain, where it is interpreted.
2.What are rods and cones?
These are special nerve cells called photoreceptor cells. They convert light information into electrical pulses for transmission to the brain.
3.Which cells are responsible for vision in low light, peripheral vision, and motion detection?
The rods are the photoreceptor cells responsible for vision in low light, peripheral vision, and motion detection.
4.Which cells are responsible for detailed and color vision?
The cones are the photoreceptor cells responsible for detailed and color vision.
5.What is the fovea?
The fovea is a very tiny area in the center of the macula. It is very densely packed with cones and is therefore responsible for the sharpest vision.
6.What is the purpose of the RPE?
The RPE delivers oxygen to and receives waste products from the rods and cones.
7.Which part of the eye nourishes the photoreceptor cells?
The RPE provides oxygen to the photoreceptor cells.
The Progression of AMD
The ways that people with AMD first discover something is wrong with their vision are varied. Some people report that the first indication was quite subtle: the need for more light. For others, vision became blurred or straight lines appeared wavy from one day to the next. For example, they may say that the edges of buildings or the line down the center of a highway looked distorted. Whether gradual or sudden, subtle or acute, these discoveries are usually surprising and shocking to the person, since the change in vision is painless and totally unexpected.
If you or someone you know has AMD, the following may be among the evident symptoms:
The level of lighting constantly seems too low.
Unclear or missing spots appear in the central vision.
Glare problems become evident.
Straight lines appear wavy.
Unnoticed items get knocked over or spilled.
Also, if any of the following tasks become difficult, it may indicate that the disease is developing:
reading and other close tasks, especially in unfamiliar places and where “stronger” eyeglasses do not help
recognizing faces and watching TV
seeing in the dark—for example, when driving at night
finding articles, even in familiar environments
judging the edges of stairs and curbs
Often the disease develops in only one eye. A situation may occur in which vision through the good eye is blocked. This can happen, for example, when a person is sitting behind another person or an obstructing pillar in a theater or concert hall. Then a blurred image appears, or the center of the image seems to be blank.
Many people think that those with AMD will eventually lose all their vision. Remember that the affected part of the eye is the macula, the part of the retina responsible for detailed, central vision. The rods in the side, or peripheral, parts of the retina continue to enable the person to see and detect movement. People with AMD do not lose all their vision from this disease. Remember also that a person may have the disease in only one eye. In that case, the other eye would compensate, and the person may not notice any visual impairment unless the sight in the unaffected eye was blocked.
This section defines AMD’s two forms, wet and dry, to describe the way AMD most often progresses.
The Dry Form of AMD
AMD diagnosed as the dry form is so named because it does not involve fluid leakage. With age, people often begin to have deposits called drusen on the retina. Small at first, so-called hard drusen are not necessarily a cause for concern and do not interfere with vision. Sometimes, however, these small, yellow spots of drusen begin to enlarge and change shape. The larger drusen are referred to as soft and are usually considered early indicators of the disease or that the disease may be progressing. Remember that drusen are not visible except to a doctor looking through special instruments.
What makes drusen form and grow? First, for reasons that are not completely understood, some of the cones in the macula begin to die. Most experts agree that the failure begins when the RPE and Bruch’s membrane, which service the photoreceptors, do not work properly. The nerve cells become incapacitated if oxygen is not supplied and waste is not removed. Over time, more of the macula may begin to degenerate and die. Consequently, these areas of degeneration result in small central areas of distorted vision.
Another early indicator of AMD is called hyperpigmentation. In this case, spots of dark color appear on the retina. Also, for unknown reasons, pigment cells sometimes form clumps in the retina. Some researchers believe the clumping is a healing response that does more harm than good, but this is not proven clinically.
Still another sign of dry AMD is called pigment epithelial detachment (PED). Drusen become very large, forming a small blister on the retina, causing this small area of retina to become detached.
The dry form can develop very slowly over many years. Sometimes small drusen form without any further development, and no visual changes occur.
The Wet Form of AMD
AMD diagnosed as the wet form is so named because it involves new blood vessel formation and fluid leakage. Ten to twenty percent of dry form AMD cases develop into the wet form. The wet form becomes evident when new blood vessels in the choroid under the retina begin to grow. These new vessels do not grow normally; they develop like a web or like the branches of a tree into the RPE under the retina. Their walls are weak and can leak blood products called exudates. In healthy eyes, Bruch’s membrane prevents such an intrusion into the retina, but for unknown reasons a breakdown can occur in the system. The progression from dry to wet form AMD can happen suddenly. The progression can happen very fast, even over a matter of hours or days.
The medical term for this process of abnormal blood vessel growth is choroidal neovascularization (CNV). Neo means new and vascular means vessels; so the term means “new vessels from the choroid.” Another term used for the wet form is subretinalneovascularization (SRNV). Subretinal means “under the retina”; so the term means “new vessels from under the retina.” Another term you may hear doctors and other health professionals use is exudative maculardegeneration.Exudative means seeping,which describes the way the abnormal blood vessels leak.
In advanced cases of the wet form, the eye tries to repair the damage caused by the leakages. This results in disc-shaped scars that cover progressively larger portions of the macula. The condition is therefore called disciform degeneration, but many professionals use the simpler terms late stage or extensive degeneration to describe the wet form with scar formation.
People with the dry form will already have lost the use of some cones, but the flooding, or transudation, that takes place in the wet form drowns or suffocates many more and can happen much more quickly. A person whose AMD has developed from the dry to the wet form will become aware that his or her vision has deteriorated dramatically. No matter how advanced the disease becomes, however, remember that AMD affects the macula, not the entire retina. People with AMD keep their peripheral vision, unless they suffer from another eye dysfunction.
Section Review
Review the information in this sectionby answering the following questions. A suggested response follows each item.
1.List the possible symptoms of AMD.
- The level of lighting constantly seems too low.
- Unclear or missing spots appear in the central vision.
- Glare problems become evident.
- Straight lines appear wavy.
- Unnoticed items get knocked over or spilled.
Also difficulty with the following:
- reading and other close tasks, especially in unfamiliar places and where “stronger” eyeglasses do not help
- recognizing faces and watching TV
- seeing in the dark—for example, when driving at night
- finding articles, even in familiar environments
- judging the edges of stairs and curbs
2.Can a person with AMD lose all vision? Why or why not?