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.