In my latest post I talked about doing a vision acuity test, so I thought it might be a good idea to explain how the test actually works. Most people have seen an eye chart in either their doctor's or their optometrist's office. It's a standard white chart with black letters in rows. From the top down, each row has more letters and the letters in the row are smaller than the letters in the row above them. Beside each row you see a score, the top one is usually 20/200, the next one is 20/100, and so on. The numerator refers to how far in feet the patient is when he or she is doing the test. The denominator refers to the farthest distance, in feet, that a person with normal vision, 20/20, can be and still be able to read that row.
During the test, the patient usually stands 20 feet away from the chart and reads aloud the smallest row of letters that he or she can. The score beside the letter represents their vision acuity. The patient usually does the test once with the left eye covered, once with the right eye covered, and then with both eyes uncovered.