BRIEF REVIEW ON TYPES OF OPTIC ATROPHY 1 PRIMARY OPTIC ATROPHY 2 POST NEURITIC OPTIC ATROPHY 3 TEMPORAL PALLOR DUE TO OPTIC ATROPHY 4 CONCECUTIVE OPTIC ATROPHY 5 ISCEMIC OPTIC NEUROPATHY 6 TRAUMATIC OPTIC ATROPHY 7 TOXIC OPTIC ATROPHY 8 DUE TO DRUGS