Combined optical coherence tomography and electroretinography (OCT+ERG) system for imaging neurovascular coupling in the human retina

SignificanceDuring their early stages of development, neurological and neurodegenerative diseases cause changes to the biological tissues morphology, physiology and metabolism at cellular level, and acute, transient changes in the local blood flow. Development of novel optical methods for quantitative imaging of such changes non-invasively and simultaneously would allow for probing of neurovascular coupling in neural tissues and therefore can have a profound effect on furthering our understanding of neurodegeneration. AimTo develop an optical imaging platform based on optical coherence tomography (OCT) for imaging and characterization of neurovascular coupling in the human retina with high spatial and temporal resolution. ApproachA fast, ultrahigh resolution OCT system was developed and combined with a clinical electroretinography (ERG) system for in-vivo, simultaneous structural, functional and vascular imaging of the human retina in response to visual stimulation. Novel image processing algorithms were developed to quantify visually-evoked physiological and blood flow changes from the OCT images and explore neurovascular coupling in the healthy human retina. ResultsVisual stimulation of the human retina with singe flashes (white light, 4ms duration) caused transient changes in the optical reflectivity and thickness (optical pathlength difference) of major retinal layers, as well as the blood flow in local retinal blood vessels. The time courses of the neuronal and blood flow changes were correlated, and their magnitude was dependent on the intensity of the visual stimulus. ConclusionsWe have developed an optical imaging modality for non-invasive probing of neurovascular coupling in the living human retina and demonstrated its utility and clinical potential in a pilot study on healthy subjects. This imaging platform could serve as a useful clinical research tool for investigation of potentially blinding retinal diseases, as well as neurodegenerative brain diseases that are expressed in the retina such as Alzheimers and Parkinsons.