Bruch's membrane opening changes and lamina cribrosa displacement in non-arteritic anterior ischaemic optic neuropathy

Purpose To describe the morphological changes in the lamina cribrosa (LC) and prelaminar tissue (PT) from eyes with non-arteritic anterior ischaemic optic neuropathy (NAION) using enhanced depth imaging (EDI) optical coherence tomography (OCT), and to evaluate whether these changes correlate with retinal nerve fibre layer (RNFL) thickness and visual acuity (VA). Design/methods A prospective case-control study was performed, including 17 study eyes with NAION and 17 control, uninvolved eyes from 17 patients. Eyes underwent scanning with Spectralis-OCT at onset, 2 and 6 months after NAION. Bruch's membrane opening (BMO), anterior LC surface depth (LCD), LC thickness and PT thickness (PTT) were compared between study and control eyes. Correlation analysis was performed to evaluate the association between these parameters, RNFL thickness and VA. Results At presentation, average PT was 58.6% thicker in NAION eyes compared with healthy control eyes (p=0.001), followed by a significant thinning at 2 and 6 months (p=0.001). A significant LC forward displacement was observed at 2 and 6 months (p=0.001). BMO progressively shrunk at 2 and at 6 months (p<0.05). A significant correlation was found between PTT and RNFL thickness (rho(Spearman)=0.544, p=0.024) at onset, as well as between PTT and RNFL changes at 6 months (rho(Spearman)=0.545, p=0.036). BMO and RNFL changes were also correlated at 6 months (rho(Spearman)=0.750, p=0.001). Conclusions At onset, a significant PT thickening, backward LC movement and BMO enlargement occurred in NAION eyes compared with unaffected eyes, and these changes significantly reversed during follow-up. PTT and RNFL changes were significantly correlated.