Hyperopia ( Farsightedness )
People with hyperopia need to make a greater effort than normal to focus. With hyperopia the effort needed to focus may cause the eyes to turn in resulting in crossed eyes and sometimes a "lazy eye" may develop.
A child with hyperopia might get more tired when reading or writing or may suffer headaches when copying from the blackboard. They may experience blurry vision at times, more often when doing close work.
With age, the focusing mechanism of the eye becomes less flexible requiring reading glasses earlier than is normal in middle age.
Even the cause is not confirmed, early detection with proper prescription can stop screwing eye happens.