Purpose: To extend ranges of accurate visual localization
Apparatus: About five feet of white elastic string, button or bead to fit string, shirt cardboard with black concentric rings, 12- to 16-inch length of broomstick.
1. Stand 48″ from concentric ring target with elastic string attached to target center and to bridge of glasses. Patient is to look at center of target.
2. Alternately cover and uncover each eye until patient learns that the right eye sees the left string and the left eye sees the right string. When two strings are reported, say, “Close tour eyes, and when you open them, look at the center of the bull’s-eye target.” If patient does not consistently see two strings when doing this, have him rotate his head. Repeat five to six times.
3. If both strings stay there (neither one disappears) have patient look at the center of target and report accurately what happens to the strings. The angle between them may fluctuate, or they may cross at different points. But have him concentrate and the strings will eventually cross at the center of the rings. Patient tries to continue to see it this way while opening and closing eyes five to six times. Repeat while gradually (an inch or two at a time) moving closer to the target (up to six inches).
4. Place bead on string. Bull’s-eye target at 48″, bead at 16″. Patient is to look at target on wall, but is to notice the presence of a bead on each string while the two strings meet at the target. When accomplished, have him look at the bead. He must see two strings crossing at ONE bead, and leading to TWO bull’s-eye targets. Now he is to close and open eyes while endeavoring to see the pattern as describe. Repeat five to six times. Now quickly change focus from bead to target. Be sure of proper crossing of string before closing eyes. Repeat as before up to six inches.
5. Devise a method of rotating the concentric ring target. For example, tack it to a 12- to 16-inch length of broomstick. The home assistant can rotate the target by turning the broomstick handle in his hands. Attach the string to the concentric ring target eccentrically with the bead attached between target and glasses. Patient should look at target and see two strings meeting at the target and also see two beads. Follow target in rotation. Note whether the two strings continue to meet at the target at all points in the rotational field. If there is a problem, discontinue rotations and repeat Step #3 in the part of the field where the difficulty is noted. Next, look at bead, making sure that strings cross at the bed and that there is awareness of two bull’s-eye targets. Now rotate the disc again, but look at the bead, making sure that the strings cross at the bead in all portions of the rotational field while still noting two targets. Place bead successively closer until patient can achieve as close as 4″ from his eye.
Aspects to be Emphasized:
1. Accurate crossing of strings at point of fixation.
2. Control of crossing point in all areas and during movement.