Differences between direct and indirect ophthalmoscopes

Ophthalmoscopy, also referred to as fundoscopy is a test that allows the eye doctor or the ophthalmologist to examine the retina, the optic discs, and the blood vessels of the region. Ophthalmoscopy is undertaken in a routine exam at a family practitioner’s clinic or by an ophthalmologist to diagnose a number of eye diseases. It may also be undertaken if you suffer from a disease that may affect the blood vessels of the eye (such as diabetes or hypertension). In fact, the retina is the only portion of the central nervous system that can be viewed from the exterior through an Ophthalmoscope. This makes it an invaluable tool when it comes to viewing the fundus (the back of the eye) and the vasculature of the eye.

Since it is an important primary care instrument, it is essential that we understand the difference between a direct and indirect ophthalmoscope before we buy these medical instruments online. An ophthalmoscope is believed to have been invented in 1847 by Charles Babbage. In about 1851, Hermann von Helmholtz revolutionized eye care by popularizing this medical device. For many decades the device used to look into the eye was a handheld, direct ophthalmoscope. The doctor holds the lens of this instrument over the pupil of the patient and looks through it by coming very close to the face of the patient. It looks like a flashlight and can magnify the interior of the eye about 15 times. It offers a smaller view of the eye (approximately 10° in diameter).

The indirect ophthalmoscope is a more recent invention and constitutes a light placed on a headband worn by the physician. In addition to the light, a handheld lens helps in the examination of the retina and the fundus of the eye. It provides an inverted image of the fundus. While the image is magnified about 2-5 times, the indirect ophthalmoscope offers a much wider view (about 35°) allowing both the central and peripheral retina to be seen clearly.

It is important to remember that a direct ophthalmoscope is generally used by family practitioners and general physicians. It does not need dilation of the pupil. Ophthalmologists and specialists, however, prefer to use indirect ophthalmologists. They also prefer to dilate the pupil before conducting ophthalmoscopy.

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