Skip to content

C.A.S.A. Vision Screeners

Self-Testing Vision Screeners

The C.A.S.A. Vision Screener is a self-testing, tri-colored eye chart designed to detect changes in vision. The distance vision test is comprised of one size Snellen letter size of 20/40, which corresponds to the minimum requirement for driving. The near vision test is comprised of Snellen letters varying from 20/200 to 20/20.

The background colors employed on this chart are green, red and yellow, which are the diagnostic colors involved in chromatic aberration of the eye. The chart has a surface of specified reflectivity so as to best manifest chromatic aberration.

The test is based on the chromatic aberration of the eye, whereby green, red and yellow light are refracted differently in the eye.

The relative clarity in one color with respect to the others relays information as to the visual state of the observer, hence, lending diagnostic value to the test; better vision in the red = myopic tendency, with or without astigmatism; better vision in the green = hyperopic tendency, with or without astigmatism; better vision in the yellow can indicate uncorrected simple hyperopic or simple myopic astigmatism, and mixed astigmatism.

The C.A.S.A. Vision Screener has a Canadian and American copyright along with a copyright protection in 172 more countries including UK.

Instructions

Disclaimers

  • The C.A.S.A. Vision Screener serves to detect changes in vision due to physiological (ie. Age related) or pathological (ie. Hyperglycemia) reasons. Color vision deficiency does not affect the results of this test.
  • Seeing clearly in every color does not mean that the vision is normal. Certain visual anomalies may still exist. Blurry vision may also be associated with other ocular diseases.
  • This visual screening technique does not replace a full eye exam. C.A.S.A. Vision recommends yearly eye examinations at the eye doctor.
  • C.A.S.A. Vision Inc., its members and affiliates assume no liability for any advice, diagnosis or other information or services that you obtain on this website.

C.A.S.A. Vision Screeners for distance and near vision tests along with the Amsler grid, test instructions and clinical applications are available only in a copyright printed testing format.

Distance
Vision Test

If you wear distance glasses (or contact lenses), be sure to have them on when taking the test. Use only the most recent prescription. This vision screening procedure can be done on a daily basis.

  1. Stand 10 feet (3 meters) from the Distance Vision Test eye chart. The test distance can vary by 10% – that is test between 9 – 11 feet.
  2. Look at the letters (words) in each colored section, using one eye at a time (covering the other eye with your hand).
  3. Focusing on the clarity of the letters (words) in each color, note whether there are differences in your ability to see in the 3 sections of colour.

Results

  • If the letters (words) are blurry in one color or more, your vision may not be safe for driving. Contact your optometrist or ophthalmologist immediately.
  • If the letters (words) are clearer in the green section, or blurry in the red section, and you have previously been diagnosed with Dry Macular Degeneration (AMD) in the past, contact your optometrist or ophthalmologist immediately.

Better vision
in RED

An observer would report better vision in the red, as a result of any of the following conditions:

  • Normal physiological progression of myopia.
  • Cataract formation.
  • Rise in blood sugar level with diabetes.

SEEING CLEARER IN THE RED MAY INDICATE A MYOPIC SHIFT WITH OR WITHOUT ASTIGMATISM.

Better vision
in GREEN

An observer would report better vision in the green, as a result of any of the following conditions:

  • Normal physiological development of hyperopia
  • Presence of central serous retinopathy
  • “Wet” form of macular degeneration

SEEING CLEARER IN THE GREEN MAY INDICATE A HYPEROPIC SHIFT WITH OR WITHOUT ASTIGMATISM.

Better vision
in YELLOW

An observer would report best vision in the yellow… mixed astigmatism:
A pure astigmat, who develops hyperopia, would result in seeing better in the yellow than the red or the green.

SEEING CLEARER IN THE YELLOW MAY INDICATE A MIXED ASTIGMATIC SHIFT.

Near
Vision Test

If you wear near prescription glasses, be sure to have them on when taking the test. Use only the most recent prescription. This vision screening procedure can be done on a daily basis.

  1. Place yourself 16 inches (40 cm) from the Near Vision Test eye chart.
  2. Look at the letters in each colored section, using one eye at a time (covering the other eye with your hand).
  3. Focusing on the clarity of the letters in each color, note whether there are differences in your ability to see in the 3 sections of colour.

Results

  • If the letters are blurry in one color or more, contact your optometrist or ophthalmologist immediately.
  • If the letters are clearer in the green section, or blurry in the red section, and you have previously been diagnosed with Dry Macular Degeneration (AMD) in the past, contact your optometrist or ophthalmologist immediately.
  • The undercorrected or uncorrected presbyopic patient will see the letters on the green background clearer.
  • Certain hyperopic patients may also see the letters on the green background clearer.
  • The overcorrected presbyopic patient will see the letters on the red background clearer (like certain overcorrected hyperopic patients).
  • Certain myopic patients, due to an overaction of accommodation for a near target, may see the letters on the red background clearer.
  • The uncorrected astigmatic patient will see the letters on the yellow background clearer.

Amsler Grid

Use your near prescription glasses that you would normally wear for reading. Use only the most recent prescription. This vision screening procedure can be done on a daily basis. 

  1. Place yourself 16 inches (40 cm) from the Amsler Grid.
  2. Using one eye at a time, look at the center dot and observe the lines of all the squares within the grid.

C.A.S.A. Vision Screeners for distance and near vision tests along with the Amsler grid, test instructions and clinical applications are available only in a copyright printed testing format.

Results

If the lines are wavy, crooked or distorted and if there are empty areas in the grid, contact your optometrist or ophthalmologist immediately.