Levitra (vardenafil) is a prescription anti-impotence drug that has already helped millions of men to improve their erection and be able to perform sexually. You are not supposed to consume grapefruit juice or any grapefruit products while on Levitra, so it's a good idea to discuss with your health care provider your diet while you are taking this medicine. Vision loss is one of the rare and serious side effects you may experience when taking this medicine. While it is not known for sure if simply taking Levitra can cause this reaction, or it can be attributed to the fact some people have a number of risk factors, such as pre-existing eye problems etc., you need to contact your health care provider immediately if you suspect you may be having this symptom.