In addition to evaluating whether you have nearsightedness, farsightedness or astigmatism, your eye doctor will check your eyes for eye diseases and other problems that could lead to vision loss. Here are some examples of the conditions that your eye doctor will be looking for: 

• Amblyopia. This occurs when the eyes are misaligned or when one eye has a much different prescription than the other. The brain will "shut off" the image from the turned or blurry eye. If left untreated, amblyopia can stunt the visual development of the affected eye, resulting in permanent vision impairment.
• Strabismus. Strabismus is defined as crossed or turned eyes. Your eye doctor will check your eyes' alignment to be sure that they are working together. Strabismus causes problems with depth perception and can lead to amblyopia.
• Eye diseases. Many eye diseases, such as glaucoma and diabetic eye disease, have no obvious symptoms in their early stages. Your eye doctor will check the health of your eyes inside and out for signs of early problems. In most cases, early detection and treatment of eye diseases can help reduce your risk for permanent vision loss.
• Other diseases. Your eye doctor can detect early signs of some systemic conditions and diseases by looking at your eye's blood vessels, retina and so forth. They may be able to tell you if you are developing high blood pressure, high cholesterol or other problems. For example, diabetes can cause leaks or bleeding inside the eye, which can lead to vision loss. It's estimated that one-third of Americans who have diabetes don't know it; your eye doctor may detect the disease before your primary care physician does, especially if you're overdue for a physical.