Healthy lifestyle. Heredity plays a role but you can eat a healthy diet, visit your ophthalmologist regularly, and protect your eyes when working with tools and machinery.
Good eye health. Nutritional medicine understands that the eye is the most metabolically active organ in the body, producing the most free radicals. To help keep eyes healthy then, decreasing the sugar intake and eating a low glycemic diet are key (this helps decrease the free radicals) and diets high in lutein, zeoxanthines and omega 3 can help.
Depends. If your are between 17-25 and study all the time, reading glasses are actually good to use. This age if you have a genetic tendency are more likely to become near sighted with a lot of reading. For everyone get checked for diabetes, eye exam periodically, teach your children not to eat dirt (some parasites there cause blindness). Wear eye protection when appropriate (working with wood, metal).