Evaluation of microvascular and structural changes in the macula and optic nerve head in patients with previous nonarteritic anterior ischaemic optic neuropathy

Purpose: This study aims to examine the structural features of the macula, choroid, optic nerve head and peripapillary retina of eyes with nonarteritic anterior ischemic optic neuropathy (NAION) and unaffected normal eyes by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) and to find out possible structural differences by comparing the obtained parameters between the groups and with healthy eyes. Materials and Methods: A total of 116 eyes, including 44 eyes of 36 patients with NAION, 27 unaffected eyes and 45 healthy eyes were included in the study. Age, gender, spherical equivalent and axial length values of the three groups were found to be similar (p>0,05 for all). The best corrected visual acuity (BCVA) and intraocular pressure (IOP) were recorded in all participants. Mean deviation (MD) and pattern standard deviation (PSD) were evaluated by visual field, subfoveal choroidal thickness by SD-OCT, vascular density (VD) and peripapillary retinal nerve fibre layer (pRNFL) thickness in the superficial capillary plexus (SCP), deep capillary plexus (DCP) and radial peripapillary capillary (RPC) plexus, central retinal thickness, foveal avascular zone (FAZ) area and perimeter and capillary density around the FAZ (FAZ FD) by OCTA. All parameters were compared between the groups. Furthermore, the relationship between pRNFL, MD, PSD and BCVA and the parameters measured in OCTA was researched. Results: Compared to healthy and unaffected eyes, BCVA, MD, PSD, all VD parameters in the SCP and RPC, all pRNFL parameters, all retinal thickness parameters (except for the central fovea), non-flow area in the SCP and FAZ FD values were lower in eyes with NAION (p<0,05 for all). Compared to healthy eyes, the MD, VD parameters (whole image, upper and lower hemi, parafoveal and temporal parafoveal VD) in SCP and temporal inferior pVD parameters in RPC were lower in unaffected eyes (p<0,05 for all). Furthermore, subfoveal choroidal thickness was lower in both eyes with NAION and unaffected normal eyes compared to healthy eyes, but statistical difference could only be demonstrated for eyes with NAION (p=0,514, p<0,05, respectively). Significant correlations were found between BCVA, MD and mean pRNFL and many parameters in eyes with NAION and unaffected eyes (p<0,05 for all). Conclusion: The OCTA revealed significant microvascular and structural changes in the macula, optic disc and peripapillary retina in eyes with NAION compared to healthy eyes. Moreover, the abnormal SCP and RPC VD parameters found in 'unaffected' normal eyes suggest that there may be vascular potential biomarkers associated with the development of NAION. However, our results need to be supported by more comprehensive and prospective studies.