How is Visual Acuity Measured ?
Visual acuity is the measure of the sensitivity of the visual system. It is expressed in Snellen notation, expressed as a fraction, where the numerator indicates the test distance and the denominator denotes the distance at which the letter read by the patient subtends 5 minutes of arc. Normal vision is expressed as 20/20 or 6/6. An acuity of 20/60 means that the patient was tested at 20feet but could only see letters that a person with normal vision could read at 60feet