Early axonal damage detection by ganglion cell complex analysis with optical coherence tomography in nonarteritic anterior ischaemic optic neuropathy.

Abstract

To investigate the ability of ganglion cell complex (GCC) analysis by optical coherence tomography (OCT) to detect early axonal damage in nonarteritic anterior ischaemic optic neuropathy (NAION), and to assess the relationship of GCC measurements with visual field defects and function parameters. Twenty-two patients with NAION participated in this retrospective case-series study. Patients underwent spectral-domain OCT measurement of retinal nerve fibre layer (RNFL) and GCC average and minimum thicknesses, best-corrected visual acuity, Ishihara test and Humphrey visual field (SITA Standard 24-2). These measurements were recorded in the acute (2-6 weeks after the ischaemic episode) and chronic (≥6 months later) phases. Spearman's coefficients were used to assess the relationship between GCC thickness and visual field defects. In the acute phase, none of the patients showed atrophy of the optic disc, while early damage was observed in the GCC average and minimum thickness in 54.54 % and 77.27 % of patients. At 6 months, the rate of patients with RNFL below normal limits increased to 90 % in the RNFL, and 92.85 % and 100 % in the GCC average and minimum GCC respectively. Spearman's coefficients indicated significant relationships of GCC in the acute phase with visual field index and mean deviation in both acute and chronic phases. A significant correlation was also found with location of the defects. GCC thickness measurement by OCT is capable of detecting early axonal damage in NAION eyes in the acute phase that cannot be detected by RNFL. GCC defects are significantly correlated with visual field globally and the defect location.