blindness can be cured!
You heard it here first. The human eye is capable of detecting whether linearly polarized light is polarized in the parallel or the perpendicular direction. Your brain simply erases the characteristic pattern that your eye produces when looking at such light. But you can train yourself to see the pattern:
The pattern is yellow, and bow-tie shaped. Some people report seeing a similarly shaped blue bow-tie at a right angle to the yellow. It is about an inch across. And appears at the center of your visual field.
If you have a pair of polarized sunglasses, you can teach yourself to see the brushes by staring at a linearly polarized source of light and rotating the glass at a rate of about 90 degrees/sec (to compensate for the rate at which your brain erases the pattern). Linearly polarized sources of light are a little hard to come by if you don't work in a laboratory, but a blue portion of sky at a right angle to the sunrise or sunset is linearly polarized and will allow this to work.