That's slightly more than the amount of caffeine in one standard cup of coffee -- though even an 8-ounce tall cup of super-charged Starbucks brew, will take you over that amount. But that 200-milligram mark is a bit arbitrary.
PVD may result from a narrowing of the blood vessels that carry blood to the legs and arms. The most common cause is atherosclerosis. Click Image to Enlarge. Other causes of PVD may include injury to the arms or legs, abnormal muscles or ligaments, or infection.VD is often found in people with problems with the arteries that supply blood to the heart (coronary artery disease). That is because atherosclerosis, which causes coronary artery disease, affects arteries throughout the body. Atherosclerosis is the buildup of plaque on the walls of the arteries.
1 If a headache follows the flashes, it is called a migraine headache.. If these flashes or lines of light occur without a headache, it is called an ophthalmic migraine, or a migraine without a headache.  Posterior vitreous detachment - Posterior vitreous detachment (PVD) is a common condition usually caused by aging. The vitreous, which lies against the retina, is the jelly-like substance that fills the center of the eye. Made mostly of water, the vitreous fluid gives the eye its shape. As we get older, the composition of the vitreous changes, and becomes less firm. This change sometimes causes the vitreous to pull on the retina. If the force of the pulling becomes strong enough, the vitreous may actually separate from the retina. When this occurs, we see flashes of light or stars. Most of the time a PVD is annoying but harmless. However, about 5% of the time, a PVD can cause a retinal tear or detachment.