Abstract
Purpose :
Endogenous flavoprotein fluorescence (FPF) imaging is an emerging functional assessment of optic neuropathies and retinopathies. An increase in FPF indicates oxidative stress in vivo due to increased blue light absorption and green light emission that reflect accumulation of oxidized flavoproteins. Mitochondrial stress is a key pathogenic mechanism for non-arteritic anterior ischemic optic neuropathy (NAION), the most common acute optic neuropathy in adults over 50 years of age. In this study, we performed FPF imaging in patients with unilateral and bilateral NAION and investigate whether metabolic stress correlates with severity of disease.
Methods :
We performed a retrospective case-control study of 28 chronic NAION eyes (21 patients, 57% bilateral) and 29 control eyes (19 patients) measuring papillary and macular FPF using OcuMet Beacon (OcuSciences, Inc.). FPF scans were performed using automatic focusing within a capture field spanning 13° in diameter. We quantified FPF using annular regions of interest of optic disc and macula using custom scripts and compared them with optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GCIPL) thickness.
Results :
Optic disc FPF from bilateral NAION patients had 66% higher FPF than that of controls (p=.027) and 11% higher than that of unilateral NAION (p=0.845). Hierarchical clustering revealed two distinct groups (NAION and control), where whole disc and sectoral FPF measurements in NAION were higher than control. There was no difference in disc FPF between unilateral NAION and controls (p=0.173), although there were significant differences in static perimetry mean deviation (MD) and OCT thickness. Spearman analysis revealed moderate negative correlations between optic disc FPF and OCT (RNFL AND GCIPL) thickness (r=-0.18 to -0.43), and static perimetry MD (r=-0.43, p<.001).
Conclusions :
In vivo imaging of optic disc FPF revealed evidence of elevated oxidative stress in unmyelinated retinal ganglion cell axons in patients with bilateral NAION compared to controls. This may reflect mitochondrial dysfunction and is consistent with selective vulnerability due to relatively lower levels of antioxidants, which increases risk of bilateral involvement. FPF is a promising novel functional biomarker to identify those at greater risk of developing more severe disease.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.