The objectives of loose prism jumps are to improve the accuracy and speed of saccadic eye movements. The procedure is always performed monocularly.

While the patient views a target monocularly, a prism is placed before the fixating eye. Because the prism displaces the image of the fixation object off the fovea, a saccade will be necessary to regain foveal fixation. The objectives are for the patient to be able to quickly and accurately regain fixation. In addition, an important goal is for the patient to be sensitive to very small amounts of prism. As discussed earlier, the goal of the therapy with saccades is to move from large, gross saccadic movements to small, fine movements. The procedure should therefore begin with a large magnitude prism, with a gradual reduction in the magnitude of the prism until the patient successfully works with 0.5 Δ. Another important variable is the size of the fixation object. Begin with larger targets (20/60) and decrease the target size until the patient can work with 20/20-size print with 0.5 Δ.

When the therapist works with the patient, the placement of the base of the prism should be varied each time (base-up, base-down, right, left, and any combination). Thus, the required direction of the saccadic eye movement will not be known in advance.

Discontinue this therapy technique when the patient is able to make an accurate rapid saccade using 0.5 Δ and a 20/20 target at both a distance and near-working distance.

The objectives of the Hart chart for saccadic therapy are to increase the speed and accuracy of saccadic fixation.

Place the Hart chart about 5 to 10 ft from the patient. Occlude the patient’s left eye with an eye patch and instruct the patient to call out the first letter in column 1 and then the first letter in column 10, the second letter from the top in column 1 and the second letter from the top in column 10, the third letter from the top in column 1 and the third letter from the top in column 10, and so forth. Continue until the patient has called out all letters from columns 1 and 10. As the patient calls out the letters, write down the responses and, when the task is completed, have the patient check his or her accuracy. Requiring the patient to check for errors is, in itself, another saccadic therapy technique. Now the patient will have to make saccades from far to near to check for errors.

Once the patient is able to complete this task in about 15 seconds without any errors, you can increase the level of difficulty in several ways. Ask the patient to continue calling out letters in the other columns. Specifically, after completing columns 1 and 10, have the patient call out columns 2 and 9, 3 and 8, 4 and 7, and 5 and 6. The inner columns are more difficult because they are surrounded by other targets (Video 8.2).

An even greater level of difficulty (Video 8.3) can be achieved by requiring saccades from the top of one column to the bottom of another. Instead of a left-to-right and right-to-left saccade, the patient will have to make an oblique saccade. For example, ask the patient to call out the top letter in column 1 and then the bottom letter in column 10, the second letter from the top in column 1 and the second letter from the bottom in column 10. Continue this pattern through the entire chart.

Many other variations to increase the level of difficulty are possible, including the use of multiple Hart charts and split Hart charts, incorporating the click of a metronome, and requiring the patient to maintain balance on a balance board while he or she is engaged in the task.

The objectives of letter and symbol tracking are to increase the speed and accuracy of saccadic fixation. These procedures are generally used with children.

Figures 8.1 and 8.2 illustrate the two workbooks. Both are designed to improve saccadic accuracy and speed. To permit the repeated use of the workbooks, we suggest that you cover the page being used with a plastic sheet and secure the plastic with a paper clip. We use overhead transparency sheets for this purpose.

As can be seen from Figure 8.1, each page of letter tracking has two or more paragraphs of what appear to be random letters. Occlude one of the patient’s eyes and tell the patient to begin at the upper right and scan from left to right to find the first letter “a” and to make a line through that letter. Ask the patient to then find the very first “b,” cross it out, and continue through the entire paragraph, finding the letters of the alphabet in order. The goal is to complete this task as quickly as possible. The therapist should time the therapy procedure. The patient’s accuracy can also be evaluated. If the patient is scanning for the very first letter “d,” for instance, and inadvertently misses it and finds a “d” later in the paragraph, he or she will be unable to find the entire alphabet sequence in the paragraph. The workbook has five different sizes of letters, creating another level of difficulty. We suggest that after the child finds and marks a specific letter, the pen be lifted off the page so that the patient will have to use saccades to find the next letter.

If the child experiences difficulty with this task, symbol tracking (Fig. 8.2) can be used. Children in the first grade will sometimes have difficulty because of a lack of familiarity with the alphabet. This can cause great frustration and make the therapy technique very unpleasant for the child. In such cases, use symbol tracking,
which utilizes large pictures, symbols, numbers, and fewer letters. The task is therefore considerably easier and is very useful with younger children or those with very severe ocular motility disorders.

Discontinue this technique when the performance in each eye is approximately equal and when the patient can successfully complete the paragraphs in about 1 minute.

The objectives of this technique are to improve the accuracy and speed of pursuit eye movements.