Imaging the optic nerve with optical coherence tomography

Abstract

Optical coherence tomography (OCT) is a non-invasive imaging technology, which may be used to generate in vivo quantitative and qualitative measures of retinal structure. In terms of quantitative metrics, peripapillary retinal nerve fiber layer (pRNFL) thickness provides an indirect evaluation of axonal integrity within the optic nerve. Ganglion layer measures derived from macular scans indirectly reflect retinal ganglion cell status. Notably, ganglion layer indices are platform dependent and may include macular ganglion cell inner plexiform layer (mGCIPL), ganglion cell layer (GCL), and ganglion cell complex (GCC) analyses of thickness or volume. Interpreted together, pRNFL thickness and ganglion layer values can be used to diagnose optic neuropathies, monitor disease progression, and gauge response to therapeutic interventions for neuro-ophthalmic conditions. Qualitative assessments of the optic nerve head, using cross-sectional transverse axial, en face, and circular OCT imaging, may help distinguish papilledema from pseudopapilloedema, and identify outer retinal pathology. Innovations in OCT protocols and approaches including enhanced depth imaging (EDI), swept source (SS) techniques, and angiography (OCTA) may offer future insights regarding the potential pathogenesis of different optic neuropathies. Finally, recent developments in artificial intelligence (AI) utilizing OCT images may overcome longstanding challenges, which have plagued non-vision specialists who often struggle to perform reliable ophthalmoscopy. In this review, we aim to discuss the benefits and pitfalls of OCT, consider the practical applications of this technology in the assessment of optic neuropathies, and highlight scientific discoveries in the realm of optic nerve imaging that will ultimately change how neuro-ophthalmologists care for patients.