The high pressure rips the tissue of the media apart along the laminated plane splitting the inner two-thirds and the outer one-third of the media apart. This can propagate along the length of the aorta for a variable distance forward or backward. Dissections that propagate towards the iliac bifurcation (with the flow of blood) are called anterograde dissections and those that propagate towards the aortic root (opposite of the flow of blood) are called retrograde dissections. The initial tear is usually within 100 mm of the aortic valve, so a retrograde dissection can easily compromise the pericardium leading to a hemopericardium. Anterograde dissections may propagate all the way to the iliac bifurcation of the aorta, rupture the aortic wall, or recanalize into the intravascular lumen leading to a double-barrel aorta. The double-barrel aorta relieves the pressure of blood flow and reduces the risk of rupture. Rupture leads to hemorrhaging into a body cavity, and prognosis depends on the area of rupture. Retroperitoneal and pericardial ruptures are both possible. The initiating event in aortic dissection is a tear in the intimal lining of the aorta. Due to the high pressures in the aorta, blood enters the media at the point of the tear. The force of the blood entering the media causes the tear to extend. It may extend proximally (closer to the heart) or distally (away from the heart) or both. The blood travels through the media, creating a false lumen (the true lumen is the normal conduit of blood in the aorta).
Causes of Metamorphopsia
Metamorphopsia can be a symptom of a number of eye disorders involving the retina or macula. Some of these conditions include the following:

Age-related macular degeneration
Epiretinal membrane and vitreomacular traction
Posterior vitreous detachment
Macular hole

Diagnosis
Tests used for diagnosis of Metamorphopsia mostly make use of subjective assessments of how a person views regular patterns. Many of these tests have a poor ability to accurately diagnose or identify a person with the disease (i.e.,poor sensitivity). The use of assessments such as a psychophysical test called preferential hyperacuity perimetry, which assesses a person’s ability to any misalignments of visual objects, may permit a more sensitive diagnosis of Metamorphopsia. Treatment and Prognosis
Metamorphopsia is a symptom of several common retinal and macular diseases, therefore treating the underlying disorder can improve symptoms. For people who have conditions such as Epiretinal membrane (ERM), Macular Holes and Retinal Detachment, decreased metamorphopsia is associated with an increase in visual acuity. Quantitative evaluation of metamorphopsia is an important step in understanding visual functions of individuals with macular disorders and is an essential tool for physicians in evaluating treatment results. Types
Dry (non-exudative, > 80%)—deposition of yellowish extracellular material in and between Bruchs membrane and retinal pigment epithelium (“drusen”) with gradual loss in vision.Wet (exudative, 10–15%)—rapid loss of vision due to bleeding secondary to choroidal neovascularization. Etymology
Gk, meta + morphe, form, opsis, sight

See also
Dysmorphopsia
Hallucination


== References ==