In medicine the ophthalmoscope was invented by Hermann von Helmholtz and is an instrument that is used to look into the human eye. Its use is crucial in determining the health of the retina and the vitreous body (corpus vitreum).

In patients with headaches, the finding of swollen optic discs, or papilledema, on ophthalmoscopy is a key sign, as this indicates raised intracranial pressure (ICP) which could be due to hydrocephalus, benign intracranial hypertension (aka pseudotumor cerebri) or brain tumor , amongst other conditions. Cupped optic discs are seen in glaucoma.

In patients with diabetes mellitus, regular ophthalmoscopic eye examinations (once every 6 months to 1 year) is mandatory to screen for diabetic retinopathy as visual loss due to diabetes can be prevented by retinal laser treatment if retinopathy is spotted early.

In arterial hypertension, hypertensive changes of the retina closely mimic those in the brain, and may predict cerebrovascular accidents (strokes).