Research on human ergonomics has determined that the optimal visual distance for reading and other close work is the Harmon Distance or “Elbow Distance”. This distance is measured by placing a closed fist under the chin and resting the elbow on a table. The point at the end of the elbow represents the closest distance a person should be from their near work.
Children working at a distance nearer than this distance are likely experiencing unnecessary visual strain, or if they do this habitually, might be expressing hidden eye muscle trouble.
A comfortable working distance minimizes eye strain from focusing, and provides an optimal scanning size for most textbooks and worksheet. Motor activities are best executed with optimal positioning of the eyes, the work surface, and the hands. Finally, the Harmon Distance also encourages good posture which is critical for long work sessions.
The reader can get an understanding of what some smaller children face in school by holding a newspaper 9-10 inches in front of the face and trying to read from it for an extended period.