Performance of any type can be measured by certain parameters... speed, endurance, agility, accuracy, and the ability to perform these functions under stress. This concept can be applied to many types of visual skills.
Visual speed can measure how quickly a patient can: focus their eyes to see clearly, converge their eyes to fuse the information into a single picture (eliminate double vision), and visual track by moving their eyes from place to place (either left to right, far to near or a combination of the two).
Visual endurance can affect how long a patient can stay on task and may affect their performance over time in reading, writing, or sports. Problems of visual endurance can cause a student to start out well but quickly get tired or "lose interest" when reading or writing.
Problems of visual agility may make the task of copying material from board to desk very difficult.
Problems of visual accuracy may affect a child’s ability to accurately judge visual location. These problems may affect a child’s ability to: write neatly, keep proper spacing between letters, words while writing, learn the alphabet, or recognize sequences of letters to spell words.
Problems with visual skills breaking down under stress can result in a student having difficulty studying in noisy conditions or being very poor at test taking.
Dr. Robert Pepper developed a test that was called the Pepper Concentration Profile to measure the breakdown of visual skills under stress.
Speed, endurance, agility, accuracy, and ability to do well under stress become increasing important in grade 4-College. They are often not as much an issue in grades K-3.
Treating these problems proactively, before they cause major learning problems, is vision therapy's goal in younger patients.