Terminology of Eye-Related Diagnostic Procedures

Terminology of Eye-Related Diagnostic Procedures
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  • 0:00 Snellen Chart
  • 0:40 Ophthalmoscopy, Drops,…
  • 2:00 Fluorescein Tests
  • 3:15 Refraction & Visual…
  • 4:30 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
How do we diagnose problems with the eye? What problems are there to diagnose? This lesson goes over vision and some of the diagnostic procedures of the eyes.

Snellen Chart

The most famous eye test in the world is probably the Snellen Chart, a chart that's used to test a person's visual acuity. If you've never heard of the term, then you've certainly seen the chart. It's commonly the one that has the really big E at the very top. The one the doctor asks you to read out loud. If you've got perfect (20/20) vision without corrective lenses, you technically should be able to see the big E at 200 feet away and the 20/20 line at 20 feet away.

That's just one diagnostic procedure related to the eyes, however. Let's go over some other ones, many of which I'm positive you remember being performed on you during a routine exam. Now you'll know what they're called!

Ophthalmoscopy, Drops & Tonometry

Think back to the last time you went to the eye doctor. They performed an examination of the eye, particularly the back of the eyeball, with an instrument called an ophthalmoscope, a procedure called ophthalmoscopy or funduscopy, where 'ophthalm(o)-' refers to the eye, '-scopy' refers to the examination of something and 'fundus' is a word for the back part of the interior of the eyeball. A variation of this is something called slit-lamp ophthalmoscopy, where a narrow beam of light is focused in such a way that it also allows for detailed examination of the front parts of the eye.

Almost certainly, you received eye drops that made your eyes dilate so the doctor could see inside the eye a bit better. These drops are technically called mydriatic drops, medicated drops that produce dilation of the pupil, something called mydriasis. The pupil is the black hole in the middle of your colorful iris.

And you likely remember a puff of air or another machine with a blue light being placed very close to your eye. That may have been unnerving, but it was necessary. What the doc was doing was measuring the pressure inside of your eye. This pressure, called intraocular pressure, is ascertained via tonometry, a measurement of the pressure inside the eye. 'Tono-' means 'pressure' and '-metry' means 'measurement.'

Fluorescein Tests

The blue neon light on those tonometry machines is actually wicked cool in my opinion. But your eye can fluoresce a nice yellow-green color even without the need for this machine. If you've ever had fluorescein staining performed on your eye, you know what I mean. Fluorescein staining is the application of a fluorescent dye onto the eye in order to visualize foreign bodies in the eye, or corneal abrasions or ulcerations. Meaning, we're looking for little superficial cuts or deep sores in the cornea, respectively.

Don't get this confused with fluorescein angiography, which is the visualization of chorioretinal vasculature after the injection of a fluorescein contrast medium. That's a mouthful! So let's simplify it. In this procedure, a specialized fluorescein dye (the contrast medium) is injected into the person. It travels to the blood vessels at the back of the eye. A camera then takes pictures of this dye moving through these blood vessels in order to see if there are any problems with blood flow in the retina or choroid, two layers at the back of the eye. By the way, angiography is broken down like this: 'angio-' means 'blood vessels' in this case, and '-graphy' means some sort of recording.

Refraction & Visual Field Tests

Those of you with good eyesight are unlikely to have had fluorescein angiography performed. However, there are two other tests you likely had performed during a routine examination, even if your vision was just fine. They are called the refraction test and visual field test.

The refraction test is a test that determines the eye's refractive error in order to figure out the best possible corrective lenses necessary for a patient's use. This is the test where your eye doctor switched lenses while you looked through a device at an eye chart and asked you which lens made your vision better and which one made it worse. The unit of measurement of the refractive power of a lens is called a diopter. Another lesson covers the refractive errors of the eye, and I encourage you to watch it to learn more about this.

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