to increased oxidative stress. Other studies have looked for inflammatory causes of damage. Thus far, the medical community is still not certain. Recent studies have begun to look at each layer individually. They found that decrease blood flow in the choriocapillaris precedes atrophy of the retinal pigment epithelium and the overlying photoreceptors. Since the choriocapillaris is a vascular layer, this may be used as an argument for why geographic atrophy could be a disease due to decreased blood flow. Wet AMD Neovascular or exudative AMD, the "wet" form of advanced AMD, causes vision loss due to abnormal blood vessel growth (choroidal neovascularization) in the choriocapillaris, through Bruch's membrane. It is usually, but not always, preceded by the dry form of AMD. The proliferation of abnormal blood vessels in the retina is stimulated by vascular endothelial growth factor (VEGF). Because these blood vessels are abnormal, these are also more fragile than typical blood vessels, which ultimately leads to blood and protein leakage below the macula. Bleeding, leaking, and scarring from these blood vessels eventually cause irreversible damage to the photoreceptors and rapid vision loss if left untreated. Diagnosis Diagnosis of age-related macular degeneration depends on signs in the macula, not necessarily vision. Early diagnosis of AMD can prevent further visual deterioration and potentially improve vision. Diagnosis of dry (or early stage) AMD may include the following clinical examinations as well as procedures and tests: The transition from dry to wet AMD can happen rapidly, and if it is left untreated can lead to legal blindness in as little as six months. To prevent this from occurring and to initiate preventive strategies earlier in the disease process, dark adaptation testing may be performed. A dark adaptometer can detect subclinical AMD at least three years earlier than it is clinically evident. There is a loss of contrast sensitivity, so that contours, shadows, and color vision are less vivid. The loss in contrast sensitivity can be quickly and easily measured by a contrast sensitivity test like Pelli Robson performed either at home or by an eye specialist. When viewing an Amsler grid, some straight lines appear wavy and some patches appear blank When viewing a Snellen chart, at least 2 lines decline In dry macular degeneration, which occurs in 85–90 percent of AMD cases, drusen spots can be seen in Fundus photography Using an electroretinogram, points in the macula with a weak or absent