BESB: GLOSSARY OF MEDICAL TERMS

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Glossary of Medical Terms

 

Acuity or Visual Acuity – describes the “sharpness” of what someone sees.  People with a good or high acuity, which may be stated as 20/20, see very well.  Someone who has a poor or low acuity sees images as blurry.   Poor acuity may also be called low vision or if very poor be called legal blindness; the numbers used to represent acuity in the legal blindness range can be 20/200, 20/400; or even 10/200.

 

To simulate different visual acuities try looking through different types of material.  First take a piece of plastic wrap and look through it.  Next try a piece of glass with a thin coat of Vaseline on it.  This will give you an idea of poor visual acuities.

 

Accommodation  the natural ability of the eye to change the shape of the lens to view objects both far and near.

 

Amblyopia  the loss of central vision in an eye after a medical condition has left the brain unable to perceive vision in the central area of the eye.

 

A.M.D.   the abbreviation for Age-Related Macular Degeneration.

 

Amsler Grid a  “low-tech” device used to test the function of the macula.  The Ansler Grid is a pattern which looks like a piece of graph paper with a large dot in the center.  When looking at the dot a person with a healthy macula should be able to see the entire grid with all lines straight and intact.  When a condition is present which effects the function of the macula, portions of the grid may appear missing or the lines appear fragmented or perhaps wavy.

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C.F.  Counts Fingers.”

 

Diopter  the unit of measurement used to describe the power of corrective lenses.

 

Diplopia  double vision.

 

Enucleation  the surgical or traumatic removal of the eye.

 

Evisceration of the eye – removal of all parts of the eye except for the sclera shell where eye muscles attach.

  {fields of sight}

Field or Visual Field – defines the quantity of vision.  For example, this can be compared to looking at a television picture.  When there is a television seen on and a person is the subject of the picture, you see just the person and all of the scene is restricted to what the camera shows.  If you were in the room speaking to the person, when you look at the person, you can see many areas around the person through what is known as peripheral vision.

Flashes When the vitreous (clear fluid, which is jelly-like and fills the middle portion of the eye) rubs or pulls on the retina, it creates an illusion of flashing lights

 

Floaters tiny clumps of  eye debris” inside the vitreous, the clear jelly-like fluid inside the eye.  Because floaters are solid, they cast a shadow on the retina (seeing portion of the eye), which causes a person to see a spot.  Floaters can have different shapes:  dots, circles, lines, or clouds, or they may be cobweb-like.

 

H.M. – hand motion.

 

Hypermetropia – farsighted.

 

Legal Blindness – defined in two ways.  The first way to define legal blindness is by visual acuity or how well someone can see.  If a person has a visual acuity of 20/20 then the vision is “perfect” in terms of visual acuity.  If the visual acuity is 20/200 or less in the better eye with corrective lenses, the person is considered to be legally blind.  The second way a person can be considered to be legally blind is by the quantity a person can see.  A normal eye can see a volume which is equal to 140 degrees.  Someone who sees 20 degrees or less in the better eye is considered to be legally blind based upon the quantity they see.

 

Low Vision – defined as insufficient and imperfect vision despite the use of corrective aids.  A person is considered to have low vision based solely on visual acuity, or how well he can see.  The person who can see only 20/70 in the better eye with corrective lenses is considered to have low vision.

 

L.P. – light perception.

Macula The retina is the “seeing portion of the eye.”   The retina functions much like a camera in {eye diagram} that it captures an image, turns the image into an electrical signal, which is sent to the brain for interpretation.  The retina has two parts: the peripheral retina and the macula.  Imagine the retina as a circle with a bull’s-eye at the center; this represents the macula which is very small.  The large area, which surrounds the macula, is known as the peripheral retina and makes up 95% of the retina.

 

In order to see fine detail, you need to look straight ahead, so that the macula can capture the fine details of an image.  Even though the macula makes up only a small part of the retina, it is one hundred times more sensitive to detail than the peripheral retina.   The macula allows you to see tiny detail, read newspaper print, and drive a car safely.

 

If you look at the word Connecticut” as shown in italicized letters you are looking at it with your macula. If you keep your eye fixed on the word Connecticut,” you are aware of the other words on the page because of your peripheral vision, but you won’t be able to read any of the other words well. If you can read them clearly, it is because you moved your eye and are looking at those words instead of at the word Connecticut.”

 

Magnification the increase in the size of an image which is being viewed. The power of a magnifying lens is measured in diopters or in “X” which is the number of times an image is enlarged.

 

Myopia – nearsightedness.

Nystagmus describes the rapid “Oscillation” or “wobbling” of the eyes.  Most frequently, the eyes move in a horizontal or left-to-right motion. Sometimes the movement is in the vertical plane, which is when the eyes move up and down.

 

O.D. – right eye.

 

O.S. – left eye.

 

OU – both eyes.

 

Peripheral vision gives you the whole picture or the “fields” that you see.  If you do not have good peripheral vision then you may see only what you are looking at directly.  To simulate a low visual field, look through a toilet paper tube, a paper towel tube, and finally through a piece of uncooked ziti.  This will give you an idea of what visual fields are.

 

Photophobia – sensitivity to light.

 

Presbyopia – the loss of accommodation (the ability to focus) on and near object viewing   This process is age related and begins around the age of forty.

 

Retina - The retina is the “seeing portion of the eye.”  The retina functions much like a camera because it captures an image and turns the image into an electrical signal which is sent to the brain for interpretation.  The retina has two parts: the peripheral retina and the macula.  Imagine the retina as a circle with a bull’s-eye at the center; this represents the macula, which is very small.  The large area, which surrounds the macula, is known as the peripheral retina and makes up 95% of the retina.

 

The peripheral retina gives us side vision, which is called ”peripheral” vision.   When we see something out of the corner of our eye, we use the peripheral vision.  This side vision does not allow us to see detail so it can’t be used to read effectively, perform tasks which require good, detailed vision, or drive a car safely.

 

Scotomas  blind spots within the normal field of vision.

 

Strasbismus – misalignment of the eyes.

 

Tunnel vision – the central portion of the vision which remains after the loss of peripheral vision.





Content Last Modified on 2/1/2007 4:00:29 PM