How Do You Read A Snellen Eye Chart (Optics)?
Have you ever wondered how on earth the doctor can tell the quality of your vision, or have you ever just been curious as to know how to determine visual acuity based on the Snellen Eye Chart. Below are some steps that can teach you how. In order to understand the way visual acuity is determined, first one must understand what is called the Snellen Eye Chart. The chart starts with a large letter at the top, and as one follows the chart to the bottom, the letters decrease in size. The letters are called optotypes. Next, beside each row of letters on the left side are numbers that are similar to 20/40. These numbers are what the doctor and their techs use to measure visual acuity. The top number is how far away you are sitting from the chart, or how far way the chart is from you by a reflection. This top number is 20 as it represents 20 feet. The bottom number, or second number, is the distance that this particular letter can be seen by a person that has normal vision that isn’t impaired
