Diagnosis: Dry (Nonexudative ) versus Wet (Exudative) ARMD

Before delving into the finer details, let's look at couple of simple things. Dry ARMD is not the same as dry eyes, i.e. the tearing of dry eyes is in the front of the eye and has nothing to do with 'leakage' in the back part of the eye. Second, using the term wet ARMD is not sophisticated - there is exudation or leakage under the retina, hence the term Exudative ARMD.

We're going to talk about Dry ARMD first and save the discussion on Exudative ARMD to the next blog. Dry ARMD may be mild, moderate or severe. The most important concept is that mild is mild and severe is severe and moderate can be on the way to becoming severe. You can see the progression on the OCT and photographs of the macula - this process takes years - be sure to look at 3-5 years of images. The Heidelberg OCT has the advantage of tracking the progress which makes the disease process easier to see.

Mild Dry ARMD consist of drusen or yellowish deposits under the retina. There are unfortunately many types of drusen and that discussion is a bit too complicated for this blog entry. Drusen are the hallmark of ARMD, i.e. a typical finding. Mild Dry ARMD is not usually associated with vision loss, however, if the druse (singular for drusen) is present in the center of the macula (foveal), i.e. subfoveal, then there might be some mild vision loss, either as a scotoma or blind spot or distortion or metamorphopsia. There is no need to treat at this point, however your eye doctor will start watching you more carefully, perhaps more often than yearly. Moderate ARMD usually involves enlargement and increased numbers of drusen and early visual disturbance can be present. This usually signals an increased risk of progression into severe Dry ARMD.

Severe Dry ARMD is typically associated with a phenomenon called Geographic Atrophy or GA for short. This phenomenon involves the destruction of the Retinal Pigment Epithelial layer and the adjacent retina. This destruction usually presents in a pattern that resembles a map, hence the term geographic atrophy. We'll talk more about the treatments in a future post but the most important concept is that the GA can be extrafoveal (outside the fovea) or subfoveal (beneath the fovea). With the former there is usually a mild amount of vision loss. In the latter, significant and permanent loss of reading vision, i.e. central vision, is present. Therefore the treatment hopes to limit the likely progression of an extrafoveal location to a subfoveal location. This treatment can not reverse the damage done by the GA.

The last comment is one I hear all the time."Dry ARMD is better than Exudative ARMD". That's not necessarily true as severe Dry ARMD is much worse than Mild Exudative ARMD. Neither one is better, however, Dry ARMD progresses slowly and Exudative ARMD progresses quickly, however, they both progress.