Download file doc, print it and Place at 3 meters away and record the smallest lines viewed with confidence (first left column). Run first with the right eye and then with the left one. If you do not even see the last line of 0.40, then halving the distance (1.5 meters) and refer to the right column. If you are not seen even the last line of 0.20, recorded as a result: 0.20 and contact your optometrist straight away. The test can be performed with the naked eye (without the help of corrections such as glasses or contact lenses) or with the correction in use. In the first case we speak of Natural Visual Acuity that if it doesn't reaches the value of 1.00 is indicative of reduced vision and you should contact your Optometrist as soon as possible. In the second case we speak of Visual Acuity with correction. Also in this case, if by your correction is not reached the value of 1.00 you must contact your Optometrist to improve the used correction.