Pathophysiology
Clinical meaning
The ophthalmoscopic examination (fundoscopy) provides direct visualization of the retinal vasculature, optic disc, and macula โ the only site in the body where arterioles, venules, and neural tissue can be observed non-invasively. The retina is a multilayered neurosensory tissue lining the posterior globe, containing photoreceptors (rods and cones) that convert light into neural signals transmitted via the optic nerve to the visual cortex. The optic disc is where retinal ganglion cell axons converge to form the optic nerve; it normally appears pink-orange with sharp, well-defined margins and a central cup (physiologic cup-to-disc ratio <0.5). The retinal vasculature consists of the central retinal artery (a branch of the ophthalmic artery) and central retinal vein, which branch across the retinal surface with arterioles appearing thinner, brighter red with a light reflex, and venules appearing wider and darker. The normal arteriole-to-venule ratio is approximately 2:3. Pathological changes visible on fundoscopy reflect systemic disease: chronic hypertension causes arteriolar narrowing, arteriovenous (AV) nicking (where stiffened arterioles compress underlying venules), flame-shaped hemorrhages, cotton-wool spots (retinal nerve fiber layer infarcts), and in severe cases papilledema. Diabetic retinopathy...