Macular edema is swelling in the macula (the center of the retina) with an alteration in the normal structure with fluid areas, exudates or even hemorrhages. The very center of the macula is called the fovea where the most precise vision occurs. This swelling invariably will affect the fovea and be seen as a central blur by the patient.
In patients with diabetes, there may be fatty materials (lipids) or blood cells that leak from the underlying small blood vessels. It is easy to understand how this can disrupt vision. Patients with adult onset diabetes ironically can develop macular edema in less time than can younger patients and those on insulin therapy. Good blood sugar control will reduce the chances of this disturbing form of diabetic retinopathy.
Macular edema can be diagnosed to some degree by the usual eye examination. However, the use of intravenous fluorescein injection will give the precise origin of the blood vessel leakages into the macular. Also, new laser scanning techniques such as the OCT, ocular computerized tomography, can provide a very accurate structural picture. When the condition becomes noticeable there are two different forms of treatment. The tried and true form of therapy has been focal laser therapy. Direct focal therapy is aimed at closing off the offending blood vessel. Grid focal therapy places the laser spots in a geometrical square pattern, which is somewhat more effective. Neither therapy is a guarantee that all leakage will be contained but it will definitely be reduced.
In the last five years, there have been many advances in the treatment of macular diseases, primarily wet macular degeneration. This involves direct injection of compounds into the eye that inhibit new blood vessel growth and leakage, or steroids, which reduce swelling and inflammation directly. The use of intravitreal drugs such as Avastin, Lucentis, and the steroid, Kenalog have been very effective in early cases of macular edema.
Laser and injection therapy provide the benefit of preserving vision. The side effect is small areas of microscopic vision loss such as not being able to tell a six from an eight on a crossword puzzle. There should be no loss of color vision or visual acuity when therapy is successful.