Tina has 20/40 vision in her right eye, and 20/20 vision in her left eye. what does each of these measurements mean?

The findings 20/40 vision in the right eye implies that when Tina is standing at a distance of 20 feet away from the eye chart, she will be able to read with her right eye what a person with normal vision can read from a distance of 40 feet away from the eye chart. Also, Tina has got 20/20 vision in the left eye, this implies that when Tina stands 20 feet from the eye chart, she will be able to read with her left eye what a person with normal vision can read from 20 feet away with the left eye. In conclusion this implies that Tina has normal vision in her left eye but a decreased vision in her right eye.