Generic Levitra, active ingredient Levitra, relaxes muscles within the penis allowing increased blood flow into the base cavities of the penis, which is necessary to achieve and maintain an erection.Levitra will boost your sexual performance by allowing the erection to be maintained all throughout intercourse. A small number of patients have lost eyesight in one eye after taking Levitra. This type of vision loss is called non-arteritic anterior ischemic optic neuropathy (NAION).NAION causes a sudden loss of eyesight because blood flow is blocked to the optic nerve.