The development of<unk>  can be broken down into proliferative and non-proliferative types. Both types cause disease by altering the normal blood flow to the retina through different mechanisms. The retina is supplied by small vessel branches from the central retinal artery. Proliferative<unk>  refers to damage caused by abnormal blood vessel growth. Normally, angiogenesis is a natural part of tissue growth and formation. When there is an unusually high or fast rate of angiogenesis, there is an overgrowth of blood vessels called neovascularization. In the non-proliferative type, abnormal blood flow to the retina occurs due to direct damage or compromise of the blood vessels themselves. Many causes of<unk>  may cause both proliferative and non-proliferative types, though some causes are more associated one type. Non-proliferative<unk>  Non-proliferative<unk>  is often caused by direct damage or remodeling of the small blood vessels supplying the retina. Many common causes of non-proliferative damage include hypertensive<unk> ,<unk>  of prematurity, radiation<unk> , solar<unk> , sickle cell<unk> , and anemic<unk>  (including secondary to vitamin B12 deficiency). There are three main mechanisms of damage in non-proliferative<unk> : blood vessel damage or remodeling, direct retinal damage, or occlusion of the blood vessels. The first mechanism is indirect damage by altering the blood vessels that supply the retina. In the case of hypertension, high pressures in the system cause the walls of the artery to thicken, which effectively reduces the amount of blood flow to the retina. This reduction in flow causes tissue ischemia leading to damage. Atherosclerosis, or hardening and narrowing of blood vessels, also reduces flow to the retina. The second mechanism is direct damage to the retina usually caused by free radicals that causes oxidative damage to the retina itself. Radiation, solar<unk> , and<unk>  of prematurity fall under this category. The third common mechanism is occlusion of blood flow. This can be caused by either physically blocking the vessels of the retinal artery branches or causing the arteries to narrow. Again, the result is reduced blood flow to the retina causing tissue damage. Sickle cell disease compromises blood flow by causing blood to sludge, or thicken and flow slowly, through the retinal arteries. Other disorders that cause hyperviscosity syndrome may also cause blood sludging. Lastly, clots or central artery thrombosis directly blocks flow to the retina causing the cells to die. Proliferative<unk>  Proliferative<unk>  during exam Proliferative<unk>  is the result of aberrant blood flow to the retina due to blood vessel overgrowth, or neovascularization. These pathologically overgrown blood vessels are often fragile, weak, and ineffective at perfusing the retinal tissues. These weak, fragile vessels are also often leaky, allowing fluids, protein, and other debris to leach out into the retina. They are also prone to hemorrhage due to their poor strength. This makes proliferative types of<unk>  more risky since vessel hemorrhaging often leads to vision loss and blindness. Many of the causes mentioned in non-proliferative<unk>  may also cause proliferative<unk>  at later stages. Angiogenesis and neovascularization tend to be a later manifestation of non-proliferative<unk> . Many types of non-proliferative<unk> es result in tissue ischemia or direct retinal damage. The body responds by trying to increase blood flow to damaged retinal tissues. Diabetes mellitus, which causes diabetic<unk> , is the most common cause of proliferative<unk>  in the world. Other causes Genetic mutations are rare causes of certain<unk> es and are usually X-linked including NDP family of genes causing Norrie disease, FEVR, and Coats disease among others. There is emerging evidence that there may be a genetic predisposition in patients who develop<unk>  of prematurity and diabetic<unk> . Trauma, especially to the head, and several diseases may cause Purtscher's<unk> .
Retinopathy
Maculopathy
Optic neuropathy
Peripheral neuropathy
Color blindness
Arthropathy
Retinal degeneration 
Ocular hypertension