Choroidal Thickness in Nonarteritic Anterior Ischemic Optic Neuropathy: a Study with Optical Coherence Tomography

Abstract

Purpose: Nonarteritic anterior ischemic optic neuropathy (NA-AION) is the most common nonglaucomatous optic neuropathy in adults over 50 years of age. It is frequently related to cardiovascular risk factors; however, its pathogenesis is not fully understood. The primary objective of this study was to evaluate choroidal thickness in patients with chronic NA-AION and the secondary objective was to evaluate the macular thickness in these patients.

Methods: This cross-sectional study compared two groups: group 1 included 25 eyes of 20 patients with chronic NA-AION and group 2 included 44 eyes of 31 healthy controls. In both groups, the choroidal thickness was measured in nine points of the posterior pole, using the enhanced depth imaging program of Heidelberg Spectralis® optical coherence tomography (Heidelberg Engineering, Heidelberg, Germany). The macular thickness was also measured using the automatic software of the same device. All the measurements were performed between 2 p.m. and 4 p.m.

Results: The mean follow-up time after NA-AION in group 1 was 58.60 ± 25.97 months. There were no statistically significant differences between the two groups regarding age or spherical equivalent (p > 0.05). The mean choroidal thickness of the posterior pole was 247.84 ± 58.93 µm in group 1 and 218.66 ± 67.59 µm in group 2 (p = 0.002). The mean macular thickness was 264.05 ± 30.45 µm in group 1 and 278.51 ± 26.81 µm in group 2 (p = 0.030).

Conclusions: Macular thickness is reduced in eyes that have had an episode of NA-AION, which is consistent with the findings of previous studies. However, this is the first study to document an increase in choroidal thickness in these eyes compared with normal controls. This fact may help elucidate the pathogenic mechanism of NA-AION. The increase in choroidal thickness may be related to a local dysfunction in vascular autoregulatory mechanisms, which may predispose to ischemic phenomena during periods of relative hypoperfusion. Future prospective studies should measure choroidal thickness in high risk individuals and in the healthy eye of patients who have had an episode of NA-AION in order to evaluate the role of this anatomic characteristic in predicting new NA-AION events.

Keywords: 612 neuro-ophthalmology: diagnosis • 452 choroid • 629 optic nerve