A Snellen eye chart is an eye chart that is used by eye care professionals or optometrist to measure visual acuity. The Snellen eye chart is developed by the Dutch ophthalmologist Herman Snellen in 1862. In this eye chart, there are rows of letters. Each row of letters are smaller in size than that above them. The eye doctor ask you to read the letters on each line to determine your prescription of your glasses.
The Snellen Eye Chart is developed and named after the Dutch ophthalmologist---Herman Snellen in 1862. It is an eye test tool that the eye care professionals use to measure visual acuity. It is printed within 11 lines of block letters, such as E. For example, the first line has only one and largest letter E, and the second line has two smaller E than that of the first line, and the following line has one more E with smaller size. The person who covers one of his/her eyes, and reads the specified letter that the eye professional gives. The smaller line can be read by the person, the more visual acuity in that eye.