The condition ‘crossed eyes’ is perhaps better known by its medical names ‘squint’ or ‘strabismus’. It occurs when the eyes are not coordinated. When one eye is looking at something, the other eye is looking in a different direction, either turned in towards the nose or looking out.
The Light Reflex Test
You can do this simple diagnostic test if you suspect a squint. Get the person to look straight ahead into the distance and shine a light from a penlight torch into the eyes at an arm’s length away. Observe the reflections of the light beam off the corneas. If both light reflexes are seen at or close to the center of the pupils, there is no squint. However, if any one of the reflections is seen off the center of the pupil, a squint is present.
Note : This test is not sensitive in picking up small angle squints. If in doubt, a professional eye examination should be done.
The Four Dot Test
You will need to source for red and green cellophane papers. For each colour, cut an 8cm diameter circular patch and tape the red over the right and green over the left eye. Look at the four illuminated dots on the screen from a distance of 10 ft. If FOUR BRIGHT DOTS are seen, no squint is present.
If two bright red dots are seen, the right eye is the fixating eye and the left eye, the squinting eye. If three bright green dots are seen, the left eye is the fixating eye and the right eye is the squinting eye.