520 L $$aIn the CNS, myelination of axons is essential for the rapid conduction of impulses down the nerve. In demyelinated or failing axons however, conduction is less efficient and requires more energy. The principal function of mitochondria is to provide energy for the axon but in doing so they generate most of the intra-axonal reactive oxygen species (ROS). Therefore and increased energy requirement will promote an increased production of ROS which could lead to significant damage to essential DNA, proteins and lipids and could eventually damage the axon. This thesis investigates the mitochondrial involvement in axonal pathology in the CNS diseases, multiple sclerosis (MS), autosomal dominant optic atrophy (ADOA) and tosomal dominant optic atrophy with cataract (ADOAC).