Before revision: The Landolt C consists of a ring that has a gap, thus looking similar to the letter C. The gap can be at various positions (usually left, right, bottom, top , and the 45° positions in between) , and the task of the tested person is to decide on which side the gap is.
After revision: The Landolt C consists of a ring that has a gap thus looking similar to the letter C. The gap can be at various positions (usually left right, bottom, top , and the 45° positions in between) , and the task of the tested person is to decide on which side the gap is.