Visual acuity” is a measurement of the clarity of a person’s vision in comparison with the average person’s vision. Lower visual acuity indicates that a person will not see details clearly from the same distance as other people. It does not necessarily indicate how the person will use their vision at close range. Some people use their vision very well despite having lowered visual acuity. Some use it very poorly despite having good visual acuity. Many things influence the ways in which a person uses vision.
Visual acuity is represented using a top and bottom number, 20/20 in the U.S. system or 6/6 in the European system. The top number (usually a 6 or a 20) represents the measuring distance. The bottom number represents how far away a normally sighted person could be and see the object which the child can see. In a person with normal vision, the two numbers will be the same. For instance, 6/60 means that what your child can see at 6 feet you can see at 60 feet. This is, of course, assuming that your vision is 6/6 (20/20 in US terms).
Some people who are extremely near-sighted have their acuity measured in even smaller terms. If a person reads the big E on the chart at the same distance as the average person, their visual acuity is measured at 20/200 or 6/60. If the person needs to bring the chart closer to see the big E, the visual acuity is measured differently depending on the distance from the big E.
If the person is unable to read, it can be recorded as hand-motion (HM), count-fingers (CF)
12 months is probably very early to have these estimates done. Even if they are done, they are not always very accurate, I don’t think. As your child grows older and can tell you more and do more things, it will become apparent what he does and doesn’t see, and even the acuity may be misleading depending on which parts of the retina are torn, detached, scarred, etc. It’s very important to rely on what you observe as well as, if not more than, the numbers.