Ophthalmoscope

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor-In-Chief: Aarti Narayan

Overview

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.

Indications

In patients with headaches, the finding of swollen optic discs, otherwise known as papilledema, on ophthalmoscopy is a key sign. This indicates increased intracranial pressure (ICP) which could be a result of hydrocephalus, benign intracranial hypertension (aka pseudotumor cerebri), or a brain tumor. Cupped optic discs are seen in glaucoma.

In patients with diabetes mellitus, regular ophthalmoscopic eye examinations every 6 months to every year is mandatory to screen for diabetic retinopathy. 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 be predictive of futurecerebrovascular accidents (strokes).

There are numerous companies other than Welch Allyn that manufacture direct ophthalmoscopes, including Heine, Riester and Keeler. Ophthalmoscopes are often sold with an otoscopes as a diagnostic set for physical exams.

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, brought forth 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, 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

• Direct ophthalmoscope
• Indirect ophthalmoscope

• Binocular indirect ophthalmoscope
• Monocular indirect ophthalmoscope

	Direct ophthalmoscopy	Indirect ophthalmoscopy
Image	Upright, virtual image, of approximately 15 times magnification	Inverted, reversed, direct image of 2-5 times magnification
Condensing lens	not too bright	bright, can be used in hazy media
Area in field of focus	About 2 disc diameters	About 8 disc diameters
Stereopsis	Absent	Present
Accessible fundus views	slightly beyond equator	up to the ora serata

Dilatation of pupils

Use of mydriatics allows better visualizing of the retina as the pupils constrict due to of light from the ophthalmoscope.

See also

• Charles Schepens
• Retinoscope
• Scanning laser ophthalmoscopy

External links

• Overview at bmjjournals.com
• A new digital hand held ophthalmoscope - sciencedaily.com -