To become a private pilot you do need to be able to pass a medical examination administered by a doctor who is authorized by the FAA, or Federal Aviation Authority.  There are three classes of medical examination, but private pilots only need a class three exam.  The others are for professional pilots, so don't worry about them at this point.  You will need to undertake these medical exams at various intervals after you have your PPL, the exact time between medicals depending on your age. There are very few serious medical conditions that will preclude you from flying; examples are bipolar disorder and coronary heart disease. But most common conditions which people worry about, such as short sight, are not a problem. Of course, medical conditions do become more common as people get older.  So in the end it is often medical issues that prevent older people from flying, or at least flying solo.