Opthalmoscopes: Seeing The Light!
Author: Gary Gordon

Ophthalmoscopes enable physicians to examine the interior of
the eye. An ophthalmoscope works by directing a tiny beam of
light through the pupil, where a physician can then examine the
lens, retina, optic nerve, optic disc, blood vessels, and macula
for ocular health. Opthalmoscopes can detect abnormalities and
pathological changes that signal disease.

The original ophthalmoscope was invented in 1847 by an English
mathematician, Charles Babbage. Babbage gave his opthalmoscope
to a physician for testing, but it was laid aside and quickly
forgotten. Unaware of Babbage's invention, a German
physician-scientist named Hermann von Helmholtz (1821-1894)
developed his own version of the ophthalmoscope in 1850.
Helmholtz immediately realized and communicated the importance
of his new invention and is therefore often credited as the sole
inventor. Helmhotz demonstrated the principle of his
ophthalmoscope by using a crude device made of cardboard, glue,
and microscope glass. By means of this ophthalmoscope, Helmholtz
was able to place the eye of the observer in the path of the
rays of light entering and leaving the patient's eye, allowing
the patient's retina to be seen.

Helmholtz eventually found that looking through the retina into
the back of the eye only produced a red reflex. Subsequently, he
attached a condenser lens to obtain an inverted image. This
image was then magnified five times. He called this mirror and
condenser lens combination an indirect ophthalmoscope. It was
used regularly for eye examinations until 1920. Helmholtz also
invented the ophthalmometer, which was used to measure the
curvature of the eye. He also studied color blindness,
physiological acoustics, the speed of nervous impulses, and
wrote the classic Handbook of Physiological Optics.

Allvar Gullstrand, a Swedish ophthalmologist who studied
physiological optics, developed another version of the
ophthalmoscope. His innovation was a slit lamp used with a
microscope, enabling physicians to locate foreign bodies in the
eye.

The modern ophthalmoscope is a hand-held instrument containing
a small battery-powered lamp that directs a beam of light into
the patient's eye by way of a mirrored prism. The observer looks
through a tiny hole in the prism and the instrument, which can
be focused by a series of revolving lenses, magnifying the
image. The lens focuses the image to give an approximation of
the spectacle lenses needed to correct a patient's vision. A
recent innovation in this technology is used in eye surgery,
whereupon it can project a laser beam to correct a detached
retina. Another innovation, called the binocular ophthalmoscope,
is used in clinical research, producing images the eye that can
be magnified 15 times.

Ophthalmoscopy is invaluable in many fields of medicine,
including:

• Cardiology
• Diabetes
• Hematology
• Medical Genetics
• Neurology
• Neurosurgery
• Rheumatology
• Family Medicine
• Pediatrics
• Internal Medicine
• Geriatrics

For patients suffering from chronic headaches, the finding of
swollen optic discs, or papilledma, is a key sign that indicates
raised intracranial pressure (ICP) which may be due to
hydrocephalus, benign intracranial hypertension, or a brain
tumor, among other conditions.

For patients with diabetes mellitus, regular ophthalmoscopic
eye exams are mandatory to screen for diabetic retinopathy.
Vision 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 strokes.


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