A student has difficulty in reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

Since the child cannot see the blackboard writing clearly, he is suffering from 'myopia' or 'short-sightedness' i.e. he can see closer things with naked eye but not distant things. Myopia can be corrected by using spectacles with concave lenses of appropriate power.