Using Red and Green: In Black and White – Part Four

And Then There Was Light 

As we’ve traveled the path through red and green activities, we’ve covered different color backgrounds, a few different activity options, and how to think through setting the conditions to help your patient achieve the desired result. Introducing light to the equation can seem to complicate matters, at least on the surface, but by applying the knowledge we’ve already gained (red +  green = black), it really becomes easier to work through.

worthOne of the most common applications of red and green light is the Worth 4 Dot test, which is shown below.  Please note the black background.  The Worth 4 Dot is done in most VT offices during the doctor’s examination and is used to test for suppression at varying distances.  To conduct the test, the patient is asked to wear the red/green filters (glasses), and is asked to report how the light appears.

If the red eye is suppressing, the patient is only capable of reporting what is visible through the green filter, which would be the two green dots plus the one white dot, totaling three. Since red and green make black, the red dot would be invisible to this patient. If the green eye is suppressed, the red eye will see one red dot plus the one white dot,  and the green dots will seem to have disappeared.


Anytime a patient is shown red or green light through red/green filters, we can expect a filter to filter response, meaning the colors will correspond. In simpler terms, red will see red and green will see green. The background color and target are always to be considered, but if we can remember the simple idea that red and green, when combined, make black, we can calculate out our desired result. In the Worth 4 Dot test, because of the background, colors may seem to disappear. Against a white background, the same activity may result in the patient reporting one of the colors there are working with ‘has turned black’ rather than disappearing, as show below.

Red Overlay

In this picture, which was taken through a red filter, the green bars appear black. How do you think it would look if the underlying chart were black?


Green Overlay

In this picture, which was taken through a green filter, the red bars appear black. How do you think it would look if the underlying chart were black?

If anything we’ve covered thus far is confusing or seems complicated, please locate some filters in your office and walk through it.  Try things filter to filter, and then filter to target, and then with a flashlight and see what ideas work for you.  Maybe even try taking things one step further and ask your doctor to walk you through it! We all learn best through experience!

Stay Tuned for Part Five: Fifty Shades of Green…and Red


Posted on January 15, 2015, in From My Perspective... and tagged , , , , , , , . Bookmark the permalink. Leave a comment.

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