Eye care professionals use standardized charts with letters, numbers or symbols in different sizes to test your distance vision as compared to other people. A classic example of an eye chart is the Snellen chart, developed by Dutch ophthalmologist, Dr. Hermann Snellen, in the 1860s. Nowadays, this chart is the most commonly used in ophthalmology and optics. There are many variations of this particular eye chart, but in general they show 11 rows of capital letters. The top row contains one letter, usually a big ”E”. The other rows contain letters that are progressively smaller.
During a traditional eye exam, the eye care professional asks you to read out the smallest line of letters that you’re still able to distinguish from a distance. The smaller the letters you can read accurately, the better your visual acuity is.
In the first part of the easee test, we use the Snellen E chart. In this test, the size and orientation of the letter E changes. By determining the smallest size that you are able to accurately report the direction that the letter E is facing, the system is able to measure your visual acuity.