The Many Visual Problems of Macular Degeneration
Richard L. Windsor, O.D., F.A.A.O.
Laura K. Windsor, O.D. F.A.A.O.
The Low Vision Centers of Indiana
(Originally Published in Vision Enhancement Magazine)
Patients are diagnosed daily with macular degeneration, but few patients are adequately counseled on how their vision will be affected. Vision loss from macular degeneration is much more than just a loss of visual acuity. It is important that we counsel these patients on the variety of visual problems they will encounter.
Decrease of Visual Acuity: “The sharpness of my vision is decreasing!” The macula is the center of our vision and when functioning properly provides our sharpest vision. In macular degeneration, this area is damaged and visual acuity of 20/20 is no longer possible. The surrounding retina can be used, but it is not as sensitive as the macula.
Visual Distortion: “I see wavy words, and the letters vary in size and look like they are distorted like in a funhouse mirror.” Damage to the retina may result in distortion and wavy vision due to the stretching and distortion to the retinal layers. Imagine you are projecting slides onto a screen when someone wrinkles the screen.
Come and Go Vision: “Now I see it. Now I don’t.” Macular Degeneration patients develop small areas of vision loss or blindness. They may see an object when it falls on the peripheral retina. Then as they attempt to look straight at the object, the image falls inside the blind spot and it disappears. During reading, parts of the words may fall inside the blind spots, causing parts of the word to suddenly disappearing.
Eccentric Viewing: “ I can see you better if I don’t look at you.” Patients must look away or turn their head to see well. This is called eccentric fixation, and it is a simple way to place the image on the peripheral retina, which is not damaged by the degeneration. Family and friends may mistakenly think the patient is not looking at them.
Photostress: “When I come in out of the sun, I don’t see well. Things look dark.” Photostress is a term used to describe beaching out of the chemicals in the rods and cones. These chemicals are created to react to light and thus create vision. Outside in bright sun, the light exposure uses up the chemicals. Unfortunately, the damaged retina may be unable to rapidly produce new chemicals and vision may seem to decrease or dark spots may appear. This is the same process we all experience when someone takes a flash picture of us, and we see a dark afterimage for a short period. Unfortunately, in macular degeneration the spot or decrease in vision may last much longer.
Photophobia: “Bright lights seem to bother me!” General light sensitivity may increase in patients with macular degeneration. Some patients are unable to tolerate bright lights in their home. Due to this photophobia, patients usually begin wearing sunglasses to help cope with the bright lights. When scars form in the retina they serve as reflectors to scatter light back off the retina causing further intolerance to bright lights.
Better Vision at Night: “I see much better at night!” The majority of the rod cells are located in the peripheral retina and are thus unaffected by macular degeneration. Rod cells function in lower levels of light allowing the patient to have better vision.
Color Vision: “I no longer see colors as well!” The macula has the highest concentration of cones, the cells that provide color vision. Thus with the degeneration of the macula, it results in damage to the cone color cells. Patient still see colors but color perception may become more and more impaired in advanced macular degeneration.
The Paradox of Peripheral Vision Sensitivity: “I see a tiny speck of paper on the floor, but I can’t see to recognize faces.” The peripheral retina is very sensitive to small objects and relative motion. With the central retina damaged, the patient may not be able to see faces straight ahead while seeing stars, lint on a shoulder or speck of paper on the floor, because they are picked up in the peripheral retina or side vision. If they try to look straight at the object, it may disappear just as words or other objects do. Family members often mistake this ability as an indication that the patient can see better than he or she claims.
Visual Hallucinations / Charles Bonnet Syndrome: “I see things that I know are not there! Am I crazy?” Visual hallucinations may occur in any patients with severe vision loss. Patients are often afraid to mention them for fear someone will think they are crazy. These arein the vast majority of cases not psychotic hallucinations, but are related to the brain misinterpreting the distorted image. This condition is known as Charles Bonnet Syndrome, and has been reported in the literature for over 200 years. Bonnet, Swiss naturalist, first described this as he observed in his grandfather.
Depth Perception: “My depth perception seems impaired!” Depth perception is a very fragile visual function. Any decrease in vision may disrupt ocular depth perception. Two full functioning eyes are required for ocular depth perception. Threading a needle and other skills that require depth perception may become difficult.
Good Days and Bad Days: “Some days I just don’t see well.” Patient often describe have some days when their vision is worse. This may be caused by light conditions, general health fluctuations and/or fluid changes in the retina.
I hope this list will help those suffering from macular degeneration and those working with ARMD patients to better understand the complex set of vision problems associated with macular degeneration.
You may reach Dr. Windsor at email@example.com or (765) 348-2020 at the Low Vision Centers of Indiana. You may reach Dr. Laura Windsor at (765) 348-2020 or email at firstname.lastname@example.org.