Hereditary optic neuropathies

Abstract

Optical coherence tomography (OCT) has improved our understanding of hereditary optic neuropathies like Leber’s hereditary optic neuropathy (LHON) and dominant optic atrophy (DOA). These diseases differentially involve different zones of retinal nerve fibers that progress around the ONH as a wave. LHON carriers show a thickening of the peripapillary retinal nerve fiber layer (RNFL) in the temporal quadrant, due to a preferential involvement of the papillomacular bundle. Once visual loss occurs, the RNFL reveals an early swelling of the temporal fibers, whose thickness start decreasing soon because of atrophy. A simultaneous thickening takes place in the inferior RNFL sectors for the first 3 months, after which the fibers begin to thin. The superior and nasal sector are involved later. Once the optic nerve is atrophic, all RNFL quadrants are thinner. Analysis of the optic nerve head (ONH) reveals that larger optic discs are associated with a better prognosis. In DOA, the RNFL reveals diffuse atrophy in all quadrants. The RNFL thinning is more pronounced in the temporal and inferior quadrants and less evident in the superior and nasal ones. Analysis of the macular ganglion cells suggests an earlier involvement of the macular area.