Have fun with strabismus!

Tips and Tricks

The Lang Pencil Test

Very easy: take a pencil in each hand. Hold them about 30 centimeters apart, and then move them towards eachother such that the tips touch. If you are unable to do this you don't have full stereopis. In all likelyhood random dot stereograms are no fun for you. Tip: when a non- strabismic person wants to do this, tell them they have to close one eye first. ;-)

Poor Men's Bagolini Striated Lenses Test

With an old pair of (sun)glasses and a bit of vaseline one can emulate the Bagolini Striated Lenses Test at low cost. Streak each lens with some grease and wipe it such it yields a striated pattern from down-left to upper-right on the left glass and from upper-left to down-right on the right glass (or the reverse of course).

You'll need that penlight again - penlights are mighty popular with MD's and those practicing kitchen science. Put the glasses on and look at the penlight. Do you see one or two lines of light crossing the penlight? Or is a piece of one of the lines missing in the middle?

This simple test indicates how much of the image of the nonpreferred eye is suppressed during vision under normal circumstances.

The Red Glass Test

Actually, green works just as well. It doens't have to be glass either - a transparent candy wrapper does the trick too. You'll also need a penlight. Look at the light from a distance of a couple of meters. Just one penlight there. Now hold the red glass in front of the eye you use the least (probably the one you know as the "lazy" one). Chances are you now see two lights - one white and one red.

If you see one pink light, you are either normal or the red filter is not dark enough.

This trick is based on the principle of retinal rivalry - the more different the images from the two eyes are, the less the brain is inclined to "superimpose" them, and the two eyes get 'dissociated'. Don't repeat this trick ten times a day or walk around with this red glass in front of one eye for hours, it confuses the heck out of your striate cortex, and you can end up with your eyes still dissociated after removal of the glass!
If you are among the crowd who sees two lights, you can be pretty sure red/green 3D stuff (with the silly looking red/green glasses) will be no fun for you. Stare at a penlight with the red/green glasses on. Looks like a thoroughly confused traffic light, right?