The Ganglion Cell Layer: the most useful part of the OCT exam for neuro-ophthalmologists?

A 25 year old man presents with painless central loss of vision in his right eye to 6/60 over a week. Left vision at 6/6 , He was. Otherwise well though admits to stress. He smoked 7.5 gm of tobacco and four standard drinks a day. Clinical , slit lamp and fundus exam normal apart from noted to have slightly swollen hyperaemic discs with a possible Drance haemorrhage on the left. No afferent pupil defect. Frequency doubled perimetry showed central scotoma right eye and some scattered defects peripherally on the left. CT brain and venogram was normal as was subsequent ant MRI scan . Standard serology was ordered and was negative. A presumptive diagnosis of optic neuritis was made and he received a course of IV methylprednisolone over 3 days without improvement. A Goldman perimetry was ordered to exclude functional vision loss and found to be normal. Humphrey Perimetry showed bilateral central scotoma. OCT scan of discs and macula were within normal limits but ganglion cell layer was markedly pathological. Mitoc ndrial DNA (mDNA) screening indicated homoplasmic 1178 G>A defect indicating Lebers Hereditary Optic Neuropathy.