Ophthalmoscope: Difference between revisions

Revision as of 19:27, 29 May 2012

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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.

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.

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

Direct ophthalmoscope
Indirect ophthalmoscope

Binocular indirect ophthalmoscope
Monocular indirect ophthalmoscope

	Direct ophthalmology	Indirect ophthalmology
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	upto the ora serata