We don’t know exactly why AMD occurs but there are some known risk factors: family history, Caucasian race and smoking
By Eva Briggs, MD
My mother-in-law recently asked me about macular degeneration. So I thought I’d look up something about this condition.
First of all, what is the macula? And what does it do?
The back of the eye, called the retina, is a layer of specialized nerve cells that convert light into electrical signal. Nerves transmit these signals to the brain for interpretation, enabling us to see. At the center of the retina is a round section called the macula, whose job is to interpret the fine details of objects in front of you. This allows you to decipher text, distinguish different faces, detect tiny movements and differentiate specific colors. When the macula is damaged or diseased, the eye can still detect light, but vision becomes blurry and lacking in detail.
Age-related macular degeneration (AMD) is an eye disease that damages the macula. It’s common and an important cause of vision loss for older adults. We don’t know exactly why AMD occurs but there are some known risk factors: family history, Caucasian race and smoking.
AMD comes in two types, dry and wet. Dry AMD, also called atrophic AMD, occurs when the macula thins with age. Wet AMD, also called neovascular AMD, is less common but often causes faster vision loss. This occurs when abnormal blood vessels grow in the back of the eye and damage the macula.
Dry AMD evolves in three stages: early, intermediate and late. In early dry AMD there are no symptoms. Intermediate dry AMD may remain asymptomatic or cause mild symptoms such as blurriness in the central vision or difficulty seeing when the light is low. In late AMD (both wet and dry), straight lines begin to look crooked or wavy. There may be an area of central blurriness which gradually enlarges or even blank spots.
Eye doctors can detect AMD during an eye exam that involves dilating the pupil. That’s one of many reasons for regular eye exams.
There is currently no treatment for early AMD. But there is a special vitamin supplement (AREDS-2) that may slow the progression of intermediate AMD. For wet AMD, treatment might include medication injection into the eye, or photodynamic therapy which consists of injections plus laser treatment.
Some people develop AMD in only one eye. There isn’t any cure for AMD. The low vision of late AMD isn’t fixed by glasses, contacts or surgery.
The good news is that there are various low vision devices and vision rehab services to help people with AMD remain active and independent. An organization called IALVS — International Academy of Low Vision Specialists — has an online directory of low vision specialists. One of my friends who is blind told me that her low vision specialist was the most helpful medical provider when she lost her vision due to a combination of diseases.
Eva Briggs is a retired medical doctor who practiced in Central New York for several decades. She lives in Marcellus.