Vision Tests

Have You Wondered What All The Different Vision Tests Are For?

Vision tests check many different functions of the eye. The tests measure your ability to see details at near and far distances, check for gaps or defects in your field of vision, and evaluate your ability to see different colors.

Visual acuity tests are the most common tests used to evaluate eyesight. They measure the eye's ability to see details at near and far distances. The tests usually involve reading letters or looking at symbols of different sizes on an eye chart. Usually, each eye is tested by itself. And then both eyes may be tested together, with and without corrective lenses (if you wear them). Several types of visual acuity tests may be used.

Refraction is a test that measures the eyes' need for corrective lenses (refractive error). It is usually done after a visual acuity test. Refractive errors, such as nearsightedness or farsightedness, occur when light rays entering the eye can't focus exactly on the nerve layer (retina) at the back of the eye. This causes blurred vision. Refraction is done as a routine part of an eye examination for people who already wear glasses or contact lenses, but it will also be done if the results of the other visual acuity tests show that your eyesight is below normal and can be corrected by glasses.

Visual field tests are used to check for gaps in your side (peripheral) vision. Your complete visual field is the entire area seen when your gaze is fixed in one direction. The complete visual field is seen by both eyes at the same time, and it includes the central visual field-which detects the highest degree of detail-and the peripheral visual fields.

Color vision tests check your ability to distinguish colors. It is used to screen for color blindness in people with suspected retinal or optic nerve disease or who have a family history of color blindness. The color vision test is also used to screen applicants for jobs in fields where color perception is essential, such as law enforcement, the military, or electronics. Color vision tests only detect a problem-further testing is needed to identify what is causing the problem.

More information regarding these different tests to come . . . .

Glaucoma 201: Side Vision Loss

Why is Glaucoma such a devastating disease? Well, two reasons. The first, of course, is that it robs you of your vision. The second is that this "thief" steals your vision slowly and painlessly, and you may not even know you have glaucoma until it's too late!

Your peripheral, or side vision is the first part of your vision to be lost in glaucoma. This is one of the reasons it's so hard to know that you have the disease, because your central vision, the vision you read and drive with, is preserved until very late in the disease.

We measure your side vision with a test called a "Visual Field" or Perimetry test. Modern testing is computerized. You place your chin on a chin rest and look into a dim, white bowl. When you see a light come into view you press a button. The readout looks like this: 

   

In the early stages you might only lose a very small portion of your vision.

In very late stages much of your side vision is gone; it can be like looking through a tunnel.

Don't let glaucoma steal your vision!