Толщина перипапиллярного слоя нервных волокон сетчатки и ганглиозного клеточного комплекса макулы у пациентов с хронической неартериитной передней ишемической оптической нейропатией

     Nonarteritic anterior ischemic optic neuropathy (NAION) is a common vascular disease in elderly patients presenting with unilateral, painless, sudden vision loss with optic disc edema [1-3]. NAION is caused by acute ischemic damage of the anterior region of the optic nerve due to reduced perfusion of short posterior ciliary arteries and afterwards it leads to apoptosis of retinal ganglion cells (RGCs) and optic nerve atrophy [4]. One might be able to indirectly document the loss of RGC by measuring the macular ganglion cell complex (mGCC) and the peri-papillary retinal nerve fiber layer (pRNFL) [5]. Spectral domain optical coherence tomography (SD-OCT) imaging is a useful device used in neuro-ophthalmological diseases [6]. Previously, a correlation between macular thickness and visual field (VF) loss [7], the thinning of the GC and inner plexiform layer (IPL) and the pRNFL [5].

    Purpose

    To investigate pRNFL and mGCC in patients with chronic phase of NAION that was analyzed by SD-OCT.

    Material and methods

    The patients who were diagnosed as chronic phase of NAION between January 2013 and May 2015 were reviewed retrospectively. The chronic phase of NAION was defined as having at least six months duration of the NAION symptom from onset.

    We obtained SD-OCT (Spectralis; Heidelberg Engineering, Heidelberg, Germany) measurements for each eye. We then quantified the thickness of the following layers: (1) pRNFL (nasal, superonasal, superotemporal, temporal, inferotemporal, and inferonasal, as well as global RNFL thickness), (2) mGCC; GC layer+IPL+macular RNFL (mRNFL), and central macular thickness (CMT). (Figure 1).

    Results and discussion

    A total of 25 patients (16 male and 9 female) with chronic phase of NAION were eligible for the study. Furthermore, the control group consisted of 50 subjects (26 male and 24 female) (Table).

     The pRNFL and mGCC thickness in eyes with chronic phase of NAION were significantly thinner in all quadrants compared to those of healthy control subjects and unaffected fellow eyes. The CMT of the eyes with chronic phase of NAION was similar to those of healthy control subjects (Table 1).

    RGCs comprise of three layers in the retina: the mRNFL (GC axons), the GC layer (GC bodies), and the IPL (GC dendrites). All three layers are defined as the GCC [5]. As the RGCs die as a result of diseases such as NAION, the GCC becomes thinner.

    Histopathology of NAION involves ischemic edema, cavernous degeneration and atrophy of the axons in the optic nerve as well as apoptosis of RGCs observed [4, 8, 9]. It appears that ischemic injury to the axons results in secondary metabolic damage to RGCs culminating in their death.

    Segmentation of macular OCT scans enables the in vivo quantification of the integrity of retinal neuronal layers. Furthermore it analyzes the neuronal integrity since it can demonstrate the thinning of mGCC and pRNFL in chronic optic nerve damage, particularly in NAION [10, 11].

    Previous studies demonstrated that chronic NAION causes a decrease in pRNFL thickness [12, 13]. In our study, it decreased in all quadrants of the eyes with chronic phase of NAION (Figure 2). Our findings were consistent with literature.

    In addition, the association between chronic phase of NAION and mGCC loss was reported in literature [5, 14]. Our study results demonstrate that the group of patients with chronic phase of NAION had significantly thinner mGCC thicknesses than the unaffected fellow eye and the control group (Figure 3). We found that the mGCC losses in patients with chronic phase of NAION were in accordance with literature [14, 15].

    Conclusion. We demonstrated that mGCC and pRNFL thickness measured by SD-OCT is capable of detecting axonal damage in chronic phase of NAION eyes.