Retinal OCT / fundus imaging

Optical coherence tomography (OCT) of the retina generates micrometre-resolution cross-sectional images of retinal layers, enabling quantification of macular thickness, retinal nerve fibre layer (RNFL) thickness and ganglion cell layer volume, while fundus photography documents the retinal vasculature and optic disc. Because the retina shares embryological origin and vascular supply architecture with the brain, retinal parameters serve as proxies for central nervous system and systemic vascular health: RNFL thinning is an established marker of glaucoma and has been associated with Alzheimer's disease, multiple sclerosis and Parkinson's disease. Deep-learning algorithms trained on fundus images can estimate cardiovascular risk factors — including age, sex, blood pressure and HbA1c — directly from the image, and emerging 'retinal age gap' AI clocks predict mortality and morbidity beyond chronological age in large population studies. OCT angiography (OCTA) extends the examination to capillary-level flow mapping without dye injection, enabling assessment of foveal avascular zone geometry as a vascular health marker.