astigmatism wheel

[cezar]

How do you perform this exercise in terms of "imaging" on line to be blacker than the other, or those that are indeed grey to be black? Do you just do it in your mind and then go with shifting on the wheel or do you have to imagine - with you eyes open - that the line get more black -> but if that's the way how to do it, because it is like creating sth out of nothing in your sight, not only in your memory, when the eyes are closed...