Background: To describe firstly three cases of Leber's hereditary optic neuropathy (LHON), one of which was preceded by contralateral branch retinal vein occlusion (BRVO) and the other two by contralateral retinal detachment plus one case of central retinal vein occlusion with full recovery and no LHON three years later in a 11778 mutation carrier. To describe secondly the comparison of visual field defects in R and L eyes in early LHON of one case. A novel mechanism is proposed to explain the almost inevitableprogression of LHON to involve both eyes. Methods: Clinical features of three Australian cases of LHON are reviewed. Results: In all three LHON cases retinal pathology (detachment or vein occlusion) was associated with decrease of vision in the affected eye 17, 13, and 0 months later. All three individuals subsequently developed LHON in the eye unaffected by the primary pathology 3, 6, and 8 months after the first eye lost vision from LHON. Conclusions: There is a high rate of progression to contralateral visual loss in LHON. This is significantly higher in comparison to glaucoma or agerelated macular degeneration. Apoptosis has been implicated as a likely mechanism of cell death in LHON. The almost inevitable involvement of the other eye within one year might suggest a direct retro-chiasmal spread of apoptosis between ganglion cells.