Ophthalmoscope

The ophthalmoscope is an instrument used to examine the eye. Its use is crucial in determining the health of the retina and the vitreous humor.

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. Ophthalmoscopes are often sold with otoscopes as a diagnostic set.

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History

Although originally invented by Charles Babbage in 1847, it was not until it was independently reinvented by Hermann von Helmholtz in 1851 that its usefulness was recognized.

While training in France, Andreas Anagnostakis, MD, an ophthalmologist from Greece, came up with the idea of making the instrument hand-held by adding a concave mirror. Liebreich created a model for Anagnostakis, which he used in his practice and subsequently when presented at the first Ophthalmological Conference in Brussels in 1857, the instrument became very popular among ophthalmologists.

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 Helmholtz's invention enabled ophthalmoscopy to become one of the most ubiquitous medical screening techniques in the world today. The company started as a result of this invention is Welch Allyn.

Types

There are two major types of ophtalmoscopes, direct and indirect.

Direct ophthalmoscope

It is an instrument about the size of a small flashlight with several lenses that can magnify up to about 15 times. This type of ophthalmoscope is most commonly used during a routine physical examination ^[2]

Indirect ophthalmoscope

An indirect ophthalmoscope constitutes a light attached to a headband, in addition to a small handheld lens. It provides a wider view of the inside of the eye. Furthermore, it allows a better view of the fundus of the eye, even if the lens is clouded by cataracts ^[2].

An indirect ophthalmoscope can be either monocular and binocular.

References

See also

• Charles Schepens
• Retinoscope
• Scanning laser ophthalmoscopy