What Causes Eyesight Problems In Children?

Sir, My 4 years son has been detected with an eye power of cylindrical 1. My doctor says, this eyesight will not go. I am wondered as how this eye sight problem occurred at this age. We generally have good intake of green vegetables and pulses in diet. My sons generally watch tv quite much, could this be the reason for the eye sight problem. My doctor says - not at all. I want to know about the probable reasons for his eyesight problem and the what to do now to improve his vision. Here this is to mention that I have a cylindrical 0.25+ eyesight while his father nas no eye sight problem.