pioneerpec: Ha! Ha! Let me explain.
A patient may be visiting a doctor for several different ailments during the course of his life. If he gets to see say a doctor of internal medicine, it could be for a high fever he has been suffering from for several days. Months later he may catch a bad cold and has a very sore throat. He consults the same doctor to get some antibiotics prescribed. Again later on after several months, his blood sugar level may have shot up and he consults the same doctor again for this new problem. As such, how can a doctor treat at one time several ailments when there is no symptoms of the disease. So far science has not progressed to that stage where one pill or shot in the arm could keep a person healthy for the whole year.
As for visiting the ophthalmologist, it is not that I suffer from any eye disease. I visit her around once a year to check my power as I wear glasses. That's all.
Hope things are clear now to you.