Ganglion cell analysis at acute episode of nonarteritic anterior ischemic optic neuropathy to predict irreversible damage. A prospective study.

PURPOSE: To assess the capability of ganglion cell-inner plexiform layer (GCIPL) thickness analysis by optical coherence tomography (OCT) to detect early neuronal loss in nonarteritic anterior ischemic optic neuropathy (NAION). METHODS: Sixteen patients with unilateral NAION participated in this prospective study. Complete ophthalmologic evaluation including visual acuity, visual field (VF) test, and spectral domain optical coherence tomography (SD-OCT) of peripapillary retinal nerve fiber layer (pRNFL) and GCIPL thickness were performed in the acute phase (within 1 week: 2.7 ± 2.1 days) and at 2 weeks, 1 month, 3 and 6 months after diagnosis. The mean time elapsed from acute episode to irreversible damage detection by GCIPL and pRNFL analysis was registered. Correlations between the GCIPL thinning and functional parameters such as best-corrected visual acuity (BCVA) and visual field indices [mean deviation (MD) and visual field index (VFI)] in acute and chronic phase were also analyzed. RESULTS: NAION eyes showed a significant thinning of the mean GCIPLminimum (min) compared to the unaffected eyes as early as 2.2 days after symptoms onset (p = 0.017) and at each follow-up visit. (p ≤ 0.003). The mean GCIPL average (av) was also thinner in NAION eyes compared to uninvolved eyes at 1 (p = 0.003), 3 (p = 0.002) and 6 months (p < 0.001). At the acute phase, 100 % of NAION eyes showed significant pRNFL thickening, while abnormal thinning was evident in GCIPLav, GCIPLmin, and GCIPL deviation map analysis in 31.3, 56.3, and 62.5 % of NAION eyes. The abnormal thinning rates increased to 43.8, 75, and 81.3 % at 2 weeks and to 62.5, 100, and 100 % at 1 month, respectively. At 2 weeks, GCIPLmin thickness significantly correlated with both acute and chronic BCVA, MD, and VFI. Furthermore, the mean superior and inferior GCIPL thicknesses at 2 weeks associated with corresponding mean inferior and superior hemifield MD at 6 months. CONCLUSIONS: GCIPL analysis by SD-OCT can be considered as a useful biomarker to establish ganglion cell damage. GCIPL min and GCIPL deviation map are abnormally thinner in 56.3 % and 62.5 % of eyes at presentation, respectively. Therefore, both parameters are abnormally thinned in more than 50 % of eyes at presentation. At 2 weeks, GCIPL min thickness significantly correlated with chronic BCVA, MD and VFI; therefore, GCIPL min thickness can predict final visual dysfunction.