Macular degeneration only affects central vision, and although it is the leading cause of legal blindness, it rarely causes total blindness. In other words, even patients with very advanced stages of the disease are able to navigate.
Early Macular Degeneration
People with early macular degeneration are asymptomatic. In later stages they may be aware of some distorsion, however in most people macular degeneration does not become vision impairing. In dry macular degeneration the findings are yellow deposits called drusen and some pigmentary changes in the macula. Many patients over the age of 50 have some drusen. At this stage there is no evidence that vitamin supplements are beneficial.
Intermediate Macular Degeneration
This is a stage where drusens are larger with usually some pigmentary changes. At this stage there is evidence that taking vitamin supplements (as per AREDS trial) there is risk reduction to advanced macular degeneration by 20-25%.
Dry Age-Related Macular Degeneration
Dry macular degeneration is a term used when there are various degrees of changes from early drusen, retinal pigment epithelial changes to more advanced atrophic changes. When there are atrophic changes (known as geographic atrophy), the function from that area of retina is lost and it manifests as a gap or mist in the central vision.
At present, although dry macular degeneration is an area of intense research as it constitutes 80-85% of age related macular degeneration, there is no effective treatment for it other than managing the risk factors and vitamin supplements. Fortunately, most people with dry macular degeneration do not progress to more advanced geographic atrophy or the wet form of macular degeneration.
If you have dry macular degeneration, and notice any sudden changes to your vision then you should tell your ophthalmologist immediately. Regular self-monitoring using the Amsler Grid is useful in picking up changes to wet macular degeneration. Patients with dry macular degeneration can develop wet macular degeneration, for which effective treatment is available if instituted in a timely manner.
Wet Age-Related Macular Degeneration
In this form of the disease, there is growth and leakage from new abnormal blood vessels under the retina and is known as choroidal neovascularization (CNV). There is weakening of the intervening layers between the retina and choroid and these new blood vessels form in response to impaired retinal nutrient supply, inflammation and the slowed transport of waste products which accumulate under the retina over many years.
When the new blood vessels leak blood or fluid under or into the retina, it causes the retina to become uneven, and results in objects or straight lines becoming distorted, wavy or blurry. Often, people become aware of a blurred patch in their central or reading vision.
Regular testing with an Amsler Grid can be helpful in detecting problems early, as newer treatments with anti-VEGF injections can stop significant damage before scarring sets in. The final stage of macular degeneration is scarring, in which there is irreparable damage to the photoreceptors and at this stage these injections are not effective.
