CASA VISION SCREENER

Is your vision better in the red, green or yellow?
Register today to find out which colour you see best in and what it means

The CASA VISION SCREENER is a self-testing vision chart, which has one size snellen letter 20/40, which corresponds to the minimum requirement for driving. 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.

Read about the history of our chart

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 myopic astigmatism, mixed astigmatism as well as some uncorrected ammetropia.
UNCORRECTED MYOPIA AND ASTIGMATISM ARE MANIFESTED USING THIS TEST.

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The CASA 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.

Changes in vision result from alterations in the refractive state of the eye due to either physiological or pathological variations.

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

A. Normal physiological progression of myopia.
B. Cataract formation.
C. Rise in blood sugar level with diabetes.

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

A. Normal physiological development of hyperopia
B. Presence of central serous retinopathy
C. "Wet" form of macular degeneration

III. 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.