Optical Coherence Tomography Angiography of Acute Non-Arteritic Anterior Ischemic Optic Neuropathy

Abstract

nterior ischemic optic neuropathy (AION) is divided into arteritic anterior ischemic optic neuropathy (AAION) which accounts for 15% of cases and Non-arteritic anterior ischemic optic neuropathy (NAION) which accounts for 85% of cases. Non-arteritic anterior ischemic optic neuropathy (NAION) is an ischemic change involves the anterior 1 mm thickness of the optic nerve head (optic disc), it affects around 10 cases per 100,000 per year in the age group over 50 (Johnson et al., 1994). Usually the patient with NAION presents in the morning with acute painless diminution of vision with dyschromatopsia. On examination, we can detect relative afferent pupillary defect in the affected eye, segmental or diffuse disc edema surrounded with splinter hemorrhages and decreased C/D ratio in the other eye (IONDT, 1998). Optical coherence tomography (OCT) is a non-invasive interferometric imaging modality developed in 1991 to image the retina in cross section, it improves in its resolution from 15 um to 3 um. In 2016 FDA approved a new modality called optical coherence tomography angiography (OCTA) depends on detection of moving RBCs in the vessels to detect the blood vessels. Moreover, this technique differentiates vascular tissue at multiple retinal levels (in depth).