Usually cataract refers to the opacity of crystal lens in eyes, which might be a little obvious. Sometimes we can tell whether a person have cataract or not depending on what their eyes look like. Eyes suffering from cataract usually are dull and cloudy. If the cataract is located on the dark colored part, then it is much more obvious. So it is not surprised that an optometrist can tell you have cataract. But instead of take his advice, I think you should go to visit your ophthalmologist to have an examination and get proper treatment. After all, cataract is the leading cause of blindness which can't be ignored. Don't use hands or unclean towel to rub your eyes. Take frequent breaks to relax eyes and muscles and change the vision focus every 1-2hours. Eye exercises are good for eye health. Arrange a healthy diet with food rich in protein, vitamin A, vitamin B, vitamin C and vitamin E. More fish as food could effectively slow down the development. Quit smoking which is very bad for eyes and overall health.