OCT shows retinal ganglion cell layer (GCL), inner plexiform layer, and peripapillary retinal nerve fiber layer (RNFL) thinning due to optic neuropathies. We hypothesize that with optic nerve head swelling in nonarteritic anterior ischemic optic neuropathy (NAION), GCL and inner plexiform loss occurs before RNFL loss detection.

Twenty-four patients with NAION participated in this prospective case-series study. Patients underwent spectral-domain OCT (Heidelberg Spectralis SD OCT; Heidelberg Engineering; Spectralis software version 5.3.2), measurement of retinal nerve fibre layer (RNFL) and combined GCL and inner-plexiform-layer (GCIPL) thickness, best-corrected visual acuity, and Humphrey visual field (SITA Standard 24–2). These measurements were recorded in the acute (within 10 days after the ischemic event), 1 month, 3 month, and 6 month after ischemia. Spearman’s coefficients were used to assess the relationship between GCIPL thickness and visual field defects.

Visual field mean deviations for the affected eyes were -17.5±9.0, -18.5±8.1, -20.7±7.7, -20.3±10.1 decibel at presentation, one month, 3 months, and 6 months after NAION, respectively. Mean average GCIPL value for the affected eyes was 79.6±10.1, 58.7±10.7, 48.5±6.0, and 50.3±8.3 μm and average GCIPL thickness in unaffected fellow eyes was 80.3±7.2, 78.5±7.5, 76.2±7.8, and 78.2±7.8 at presentation, one month, 3 months, and 6 months, respectively. Mean average RNFL thickness for NAION eyes was 226.2±79.9, 141.5±48.7, 65.0±18.9, and 54.7±20.1 µm at the similar time intervals. At 1 month, GCIPL but not RNFL thickness correlated with LogMAR acuity (r=-0.62, p<0.001) and visual field mean deviation (r=-0.79, p<0.001).

GCIPL thinning occurs prior to RFNL thinning in NAION, making it a better structural marker of early neuronal loss.