Analysis of Fundus Photography and Fluorescein Angiography in Chinese patients with different stages of non-arteritic anterior inschemic optic neuropathy

ABSTRACT Purpose: The aim of this study was to characterize the different stages of nonarteritic anterior inschemic optic neuropathy (NAION) features by Fundus Photography (FP) and Fluorescein Aniography (FA) in a Chinese Population. Methods: The retrospective observation study included 30 patients (36 eyes) with acute phase, 20 patients (27 eyes) with subacute phase and 30 patients (52 eyes) with chronic phase. Macular, optic nerve and disc were investigated by FP and FA. Categorical variables were evaluated by Fisher’s exact test. Results: Macular edema, papilloedema, disc hemorrhage and exudation from FP were more common in the acute and subacute stage groups than chronic stage group with optic atrophy in contrast (all p<0.01). Compared to chronic stage, acute and subacute stages were more likely to appear macular fluorescence accumulation and peripapillary choroid filling delay (all p<0.01). However, chronic stage tended to have retinal artery filling delay and disc filling defects in the early phase from FA (all p<0.01). Conclusion: The data showed that NAION had different fundus performances at different clinical stages. They may help to record the disease progression for accurate diagnosis and treatment.

degree of ischemia in the optic-nerve head could be a new way to understand the pathogenesis of NAION for further diagnosis and treatment.
Fundus Photography (FP) and Fluorescein Aniography (FA) have become more common in the evaluation and management of patients with optic neuropathies, such as NAION.
Although disc edema and peripapillary hemorrhages by FP could be suggestive in the diagnosis of NAION, it may be insignificant in cases without definite features 5

Methods
Our study is a retrospective observational study reviewing hospitalized patients who were diagnosed with NAION in the Neuro-Ophthalmology Department of Chinese People's Liberation Army General Hospital (PLAGH). The institutional ethics committee in PLAGH approved this study. Helsinki Declaration was performed in adherence with the tenets. All subjects written were informed consent.

Patients
Patients were recruited between December 2012 and December 2018. We performed full ophthalmologic examinations including systematic neuro-ophthalmologic history collection, best-corrected visual acuity, slit-lamp examination, pupillary reaction, visual field inspection, electrophysiological examination and other fundus examinations. The diagnosis of NAION was defined clinically: (1) painless rapid loss of visual acuity, (2) relative afferent pupillary defect, (3) characteristic visual field defect, (4) apparent nerve changes in the fundus. Patients were excluded with any following conditions: (1) arteritic anterior ischemic optic neuropathy (AION), (2) other diseases that cause optic neuropathy, such as toxic and traumatic optic neuropathy, (3) history of other ocular diseases, such as glaucoma and retinal diseases, (4) systemic diseases, such as tumor and epilepsy, (5) severe turbidity of refractive media and difficulty in cooperation with FA examination.

FP and FA examination
FP and FA examination was performed using a digital fundus camera (Kowa Nonmyd 7, Japan; HRA spectralis, Heidelberg engineering, Germany) according to the standard protocols. In the FP, macular edema, optic atrophy, papilloedema, disc hemorrhage and exudation were compared among different clinical stages of NAION. The non-affected eye was investigated as well. In the FA, we recorded the whole process of optic disc fluorescence filling, and performed comprehensive imaging recording of binocular optic nerve and retina. The macular fluorescence accumulation, peripapillary choroid filling delay, disc filling defects and retinal artery filling delay were focused during the whole process.

Statistical Analyses
All statistical analyses were performed using Graph Pad Prism Software (GraphPad Software Inc., USA). Categorical variables were evaluated by Fisher's exact test. P<0.05 was considered statistically significant.

Clinical Characteristics
Final analyses enrolled 80 patients (32 men and 48 women) including 113 eyes. The mean age of this study is 64.26±8.12(40-80 years). According to the onset time, this study was divided into three groups: acute stage group (<1 month), subacute stage group (1-6 months) and chronic stage group(>6 months). Acute stage group contains 30 patients with 6 patients (20.00%) experienced bilateral involvement (Table 1). Among 20 patients in the subacute stage group, 7 patients (35.00%) were bilateral NAION, which did not differ from the acute stage group (P=0.33). The chronic stage group (30 patients) had 22 patients (73.33%) who suffering the bilateral NAION, which was significantly higher compared with the acute and subacute stage groups (P<0.01).   The current FA research of NAION mainly focus on optic nerve head in acute stage. We summarized the related researches in acute stage of NAION among old patients, which was consistent with our research 5,10,18 (Table 4). There was a decreasing trend in macular fluorescence accumulation among these three groups, though acute and subacute stage groups having no significant difference (P=0.3654). These data could be statistically significant with more cases involved. In the acute stage of NAION, the optic disc is not   None.

Funding
No funding was received by neither of authors.

Availability of data and materials
Not applicable, same reasoning.