Posterior segment spectral domain oct in the differential diagnosis of bilateral temporal optic neuropathy and its correlation with visual acuity

Purpose: To identify the underlying etiologies and to evaluate the differential diagnostic value of posterior segment spectral domain OCT measurements and their correlation with best-corrected visual acuity (BCVA) in a group of patients with OCT documented bilateral optic neuropathy limited to the temporal quadrants.

Methods: Retrospective study.

Results: We included 61 patients: 35 presented with presumed "classic" acquired mitochondrial optic neuropathy (MON) (18 nutritional, 11 toxic, 6 mixed toxic-nutritional) and 2 with suspected hereditary MON. Nine patients were identified as 'MON mimickers' (especially multiple sclerosis), and 4 were found to have a mixed mechanism, while 11 remained undiagnosed. Across all etiologies, the strongest positive relationship between BCVA and tested OCT parameters was with macular GCL (ganglion cell layer) and GCIPL (combined ganglion cell and inner plexiform layer) volumes rather than peripapillary retinal nerve fiber layer (RNFL) thicknesses (all statistically significant). There was an inverse relationship between BCVA and inner nuclear layer (INL) volumes, with significant differences for BCVA and all tested OCT parameters between eyes with and without INL microcystoid lesions. OCT (absolute values and intereye differences) was not helpful in distinguishing between presumed acquired mitochondrial disease and patients with multiple sclerosis without optic neuritis. However, significantly greater intereye differences in global RNFL and inner plexiform layer and GCIPL volumes were found in patients with a previous history of unilateral optic neuritis.

Conclusions: The strongest positive relationship with BCVA was found for macular GCL and GCIPL volumes. OCT could not differentiate between acquired mitochondrial disease and multiple sclerosis without optic neuritis.