Systemic health conditions such as diabetes or high blood pressure (hypertension) can also cause retinal problems. Diabetic retinopathy can be classified as Proliferative (PDR) or Non-Proliferative (NPDR). When the retinal blood vessels develop small leaks it is called NPDR. These leaks can seep fluid or blood under the macula (called macular edema), resulting in blurred central vision. Retinal blood vessels can also become obstructed and the part of the retina being nourished by these vessels will no longer work properly. These areas then foster new blood-vessel growth called neovascularization. These new blood vessels are abnormal and leak, causing bleeding and scar tissue to form, thus resulting in severe vision loss or blindness. PDR is the type of retinopathy characterized by the growth of these abnormal retinal vessels (neovascularization). Your eye doctor may request photographs of your eyes to better determine the degree of your retinopathy. This could be a simple color photo of the retina (back of your eye), or a dye test called fluorescein angiography. With fluorescein angiography, a small amount of fluorescent dye is injected into your arm and tracked through your retinal vessels with a special camera and filters. Another form of photography may involve technology that shows a cross section of your macula, to measure the amount of edema or swelling present. This is called Optical Coherent Tomography(OCT). Laser treatment is often used in treatment of both types of diabetic retinopathy, although PDR may often require additional surgery call vitrectomy to remove blood and scar tissue from the eye. Also being used in the treatment of macular edema are medications injected directly into the eye, known as Anti-VEGF Medications (i.e. Avastin or Lucentis). The retinal vessels can also be affected by high blood pressure (hypertensive retinopathy). Prolonged elevated pressure in these small vessels can result in damage that causes leakage and swelling in the retina. Blood clots can form in the small retinal vessels, sometimes causing permanent vision loss. Depending upon the location and type of vessel occluded, laser or intravitreal injection may be recommended.