Age-related macular degeneration
Age-related macular degeneration (ARMD) is the most common cause of irreversible blindness in North America and one million Canadians will have some form of ARMD.
The macula is the central part of the retina, the light-sensitive layer that lines the back of the eye, and serves to provide vision for fine detail and reading. Macular degeneration is a chronic disease that impact the macula, and in severe forms can reduce central vision through damage and thinning of the retina.
What causes macular degeneration?
Many factors are known to be associated with ARMD:
- Age. ARMD is most common in patients over 60.
- Family history and genetics. ARMD tends to run in families and several genes have been identified.
- Race. ARMD is more common in caucasians.
- Smoking significantly increases the risk of ARMD.
- Obesity and cardiovascular disease can increase the risk of developing ARMD.
What are the symptoms of macular degeneration?
Many patients with ARMD have early forms of the disease and maintain good vision. If the disease progresses and central vision becomes impacted, patients usually describe difficulty with reading fine print, sometimes noticing words missing on a page. Patients with ARMD may describe distortion, where a straight line will be twisted, or missing a section. Sometimes patients struggle with seeing central details, for example where they can recognize a person but cannot see all their facial features.
In the most severe stages, patients can lose their central vision and be unable to read or see details. Patients with ARMD usually retain good peripheral vision and sometimes can be trained by a low vision specialist to use specialized glasses and low vision aids to use their peripheral vision more effectively.
How is macular degeneration diagnosed?
ARMD can be diagnosed with a dilated eye examination. It usually starts with the development of small deposits under the retina called drusen. Patients with these deposits often have normal vision or only mild vision changes.
Dry macular degeneration:
In dry ARMD, drusen deposits can continue to accumulate under the retina. Patients with moderate or severe drusen deposits may benefit from specialized vitamin supplements available over-the-counter at the pharmacy called AREDS2.
At a later stage, dry ARMD can lead to thinning of the overlying retina. This progression tends to be slow, and the central vision becomes severely impacted only in advanced stages with loss of the overlying retina. Currently there are no effective treatments for dry ARMD.
Wet macular degeneration:
In wet ARMD, abnormal vessels grow in the layers below the retina and leak blood or fluid into and under the retina.
This progression usually happens suddenly, with secondary blurring or distortion of the central vision. Wet ARMD can lead to scarring and thinning of the overlying retina and permanent central vision loss, but an effective treatment can halt progression and often improve the vision.
How is macular degeneration treated?
Patients diagnosed with ARMD require regular examinations with their optometrist or ophthalmologist. Patients who develop wet ARMD are referred to an ophthalmologist for treatment with intravitreal injections of anti-VEGF medication. Anti-VEGF medications are antibody fragments designed to target and suppress vascular endothelial growth factor (VEGF), a protein that promotes blood vessels to grow and leak. This helps to prevent ongoing damage to the retina light receptors. The fluid under and within the retina should slowly resolve over the course of months and the vision will often improve and stabilize.
What can I do to reduce my risk of developing vision loss with ARMD?
Patients with early stages of ARMD should get yearly screening eye examinations with their optometrist. Smoking cessation/avoidance is essential and a diet of dark leafy greens, like kale, omega 3 and antioxidants is encouraged. UV protection from the sun with sunglasses/hats is a good idea. Currently there is no clear role for genetic testing in ARMD, but this may change as research helps guide evolving treatments.
Patients with moderate to severe forms of ARMD should be referred to an ophthalmologist for assessment and monitoring. Based on the severity of your diseases, they will decide how frequently you need to be seen.
Patients with new onset of wet ARMD need immediate referral to an ophthalmologist for evaluation and treatment.