Types of MD
Dry MD
Dry MD is sometimes as referred to as atrophic. This form can be identified by yellowish deposits that look like debris in the retina. The debris material is actually called drusen. In a healthy eye, the drusen is carried away by the blood vessels in the retina. With dry MD, this process quits working properly. The exact cause of this disease has yet to be identified. It is felt that diets, genetics and the environmental could potentially be factors that contribute to the disease.
A person with dry MD may transition through three separate stages. At the onset the disease or the early stage, you can physically identify several small or a few medium sized drusen in the eye but there are no obvious symptoms or loss of vision. The intermediate stage can be identified by many medium drusen or one large drusen in the eye. A blurred or blind spot may begin to occur in the central field of vision. Objects may also appear distorted. A person will need more light or higher contrast in order to see properly. The final advanced stage is often referred to as “Geographic Atrophy”. At this stage, the photoreceptor cells in the macula that sense light begin to break down. The distortions of the person’s central vision become larger. Detailed vision is all but lost leaving patients with only their peripheral sight. There is currently no cure for dry MD, but experts believe that through stem cell research, one could be found with the next decade.
Wet MD
In the case of wet MD (also called exudative), blood vessels under the retina and macula mutate in a condition also called choroidal neovascularization (CNV). The blood vessels cause the macula to bulge. This is a result of blood or fluid leaking into the macula. The patient will see dark spots in the center of their field of vision, but the peripheral vision remains fine. Straight lines can appear wavy because of the unnatural bulging of the macula. Unlike dry MD that progresses slowly, wet MD can lead to rapid severe loss of vision. Patients that are in high risk for that disease need to have their vision checked often.
The two forms of CNV are classic and occult. The classic form is easy to define because of the obvious leaking blood vessels and it is usually the most aggressive. The occult form is harder to define because the leaking blood vessels are hidden underneath the fovea layer. This form tends to progress the slowest out of the two. Once a patient has CVN develop in one eye, they have an 87 percent chance of having it occur in the other eye within five years.
CNV does have some treatment options. The first treatments proven successful were laser treatments. Photocoagulation involves using a laser to cauterize the leaking vessels. Photodynamic Therapy is a process of injecting a light-sensitive drug into the patient’s veins and then using a laser to coagulate the leaking vessels. These laser treatments were only practical on certain types CNV and the issues often reoccur within a couple years requiring more treatment. Other types of treatments that are becoming popular include antiangiogenic drugs that prevent blood vessels from developing in the retina and surgical options such as removing the infected membrane or rotating the macula to healthy part of the retina.