Choroidal Thickness in Nonarteritic Anterior Ischaemic Optic Neuropathy: A Study with Optical Coherence Tomography

Abstract

Nonarteritic anterior ischemic optic neuropathy (NA-AION) is the most common nonglaucomatous optic neuropathy in adults over 50 years of age. It is usually related to cardiovascular risk factors. The primary objective of this study was to evaluate choroidal thickness in patients with chronic NA-AION, and the secondary objective was to evaluate macular thickness in these patients. This cross-sectional study compared two groups: group 1 included 20 eyes of 20 patients with chronic NA-AION, and group 2 included 31 eyes of 31 healthy controls. In both groups, the choroidal thickness was measured using the enhanced depth imaging program of Heidelberg Spectralis Õ optical coherence tomography (Heidelberg Engineering, Heidelberg, Germany). The macular thickness was also measured using the automatic software of the same device. The mean follow-up time after NA-AION in group 1 was 57.17 ± 26.92 months. The mean choroidal thickness of the posterior pole was 244.38 ± 61.03 mm in group 1 and 214.18 ± 65.97 mm in group 2 (p = 0.004). The mean macular thickness was higher in group 2. Macular thickness is reduced in eyes that had an episode of NA-AION, whereas choroidal thickness is generally higher in these eyes when compared with normal eyes. The increase in choroidal thickness may be due to a local dysfunction in vascular autoregulatory mechanisms, which may predispose to ischemic phenomena.

Evaluation of Choroidal Thickness in Non-arteritic Anterior Ischaemic Optic Neuropathy at the Acute and Chronic Stages

“…It has been reported that choroidal changes may be involved in retinal and optic nerve diseases such as chronic NAION because the choroid plays a vital role in supplying oxygen and nutrition to the outer layers of the retina, or RPE, and to the pre-laminar portion of the ONH. 2,17 However, one study has investigated this relationship between NAION and CT in patients who have acute NAION. 19 Our study results demonstrate that the groups of patients with acute and chronic NAION have no significant difference in terms of CTs compared with the control group and the internal control generated from the unaffected eyes of these NAION patients with unilateral disease.…”

“…However, taking OCT measurements at one selected point and comparing them with each other is not the most precise method for determining CTs, since these measurements, which are performed manually, may be affected by local irregularities of the choroid-scleral boundary. 17,21,22 Therefore, to reduce the risk of mistakes caused by this, we used three horizontal sections for the CT measurements, which were evaluated on these sections at three points, and used the average of these three measurements for comparisons. Also, the development of automatic software for CT measurements will, in the future, help to improve the accuracy of these measurements.…”

“…However, Dias-Santos et al have reported that the mean CT is significantly higher in patients with chronic NAION as a marker of the local dysfunction of the vascular auto-regulation mechanisms. 17 These authors have also hypothesised that dysfunction of the vascular auto-regulation might be present before an ischaemic attack, and that this can make a person more vulnerable to experiencing an ischaemic event. However, our results have not supported this hypothesis, since there are no changes in the CTs of patients with acute NAION and no differences in the CTs in the contralateral eyes of patients who had both acute and chronic NAION in our study.…”

“…However, our results have not supported this hypothesis, since there are no changes in the CTs of patients with acute NAION and no differences in the CTs in the contralateral eyes of patients who had both acute and chronic NAION in our study. Dias-Santos et al have also reported that the macular tissue, which is decreased in patients with chronic NAION, might be associated with the increase in CT. 17 They have hypothesised that the decrease in macular thickness reduces the metabolic activity of the decreased retinal tissue, and since this could interfere with the choroidal vascular auto-regulation in that area, CT increases in patients with chronic NAION. However, it is not clear whether the choroid has appreciable vascular autoregulation.…”

“…They were also measured at the centre (foveal meridian) and at 1500 μm in the nasal and temporal directions. 17 Each horizontal section included three CT measurements for a total of nine CT measurements acquired from each eye. Three were located at 1500 μm nasal to the foveal meridian at these three horizontal sections.…”