Ophthalmoscope

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The ophthalmoscope, invented by Hermann von Helmholtz, is an instrument used to examine the eye. Its use is crucial in determining the health of the retina and the vitreous humor.

In 1915, Willam Noah Allyn and Frederick Welch invented the world's first hand-held direct illuminating ophthalmoscope^[1], precursor to the device now used by clinicians around the world. This refinement and updating of von Helmoltz's invention enabled ophthalmoscopy to become one of the most ubiqutous medical screening techniques in the world today. The company started as a result of this invention is Welch Allyn.

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).

There are numerous companies other than Welch Allyn that manufacture direct ophthalmoscopes, including Heine, Riester and Keeler.