Abstract

Diabetic retinopathy (DR) is a chronic progressive sight-threatening disease of the retinal microvasculature associated with prolonged high elevated blood sugar levels (hyperglycemia) as well as other linked conditions such as hypertension. DR can be asymptomatic for long periods and as the disease progresses, patients can experience mild sight impairments. However, late stages of the disease can lead to severe sight- threatening conditions and potential blindness, if untreated. Vision loss can occur secondary to either leak in the center of the retina (macula)—leading to diabetic macular edema—or due to the development of new vessels that can bleed inside the eye. DR can manifest in forms of blurred and/or fluctuating vision, dark spots fluctuating during saccades, empty vision areas, and reduced vision. From a clinical perspective, DR can be classified as a nonproliferative stage (NPDR) or as a more ad- vanced proliferative stage (PDR). In NPDR, damages occur in the inner retinal blood vessels, which leak of fluids onto the retina, resulting in edema and swelling [1]. In this scenario, Frank [2] defines lesions as the major sign of retinopathy, and clusters them as microaneurysms (MAs), hemorrhages (HMs), hard and soft exudates (EXs), intraretinal microvascular abnormalities (IRMA), and venous beading (VB). NPDR can be graded as mild, moderate, or severe. Mild NPDR occurs with at least one MA. Moderate NPDR occurs with scattered retinal deep dot and blot HMs, and/or cotton wool spots CWS (soft exudates) and IRMAs but not as extensive as severe NPDR. The diagnosis of severe NPDR is based on the 4:2:1 rule of the ETDRS [2a]. Furthermore, IRMA can be present in each quadrant. With respect to PDR, abnormal development and angiogenesis of new vessels are the main representative character- istics of the disease: new blood vessels can grow in different areas of retinal surface or at the surface of the optic disc. The former are defined as New Vessels Elsewhere (NVE), the latter as New Vessels on Disc (NVD). These abnormal new vessels can easily bleed and are considered as the major leading cause of DR-related blindness.