Illinois Vision Certification Practice Test

The Snellen system standardized the size of letters or symbols for persons of normal visual acuity to correctly identify that symbol at varying what?

1. Brightness, Distances

2. Size, Distances

3. Shape, Angles

4. Color, Speeds

The correct answer is: Size, Distances

The Snellen system is a widely used method for measuring visual acuity, which is a standard for vision testing. It establishes a framework where letters or symbols are presented in a specific size that can be accurately identified by individuals with normal vision at various distances. The fundamental aspect of this system revolves around the relationship between the size of the letters or symbols and the distance from which they are viewed. The chart is designed in such a way that each line corresponds to a specific size of letters, and as one moves further away, a person with normal visual acuity should still be able to identify the symbols clearly. This creates a scalable measure of visual performance that adjusts based on distance while maintaining the adequacy of size for optimal evaluation of vision. Thus, the correct choice emphasizes the importance of both letter size and the distance at which they are viewed when determining visual acuity through the Snellen system.