Refraction and muscular imbalance, as simplified through the use of the ski-optometer

by Daniel Woolf

Prisms

1st. Where a case cannot be reduced through use of first two methods, as for example in a case of 6° of exophoria, prescribe ¼ of amount of imbalance (¼ × 6 = 1½°) for each eye—base in—or esophoria base out, hyperphoria base up on eye affected.

2nd. Advise patient to call every three months and make duction test ([Fig. 24]). If no improvement in condition, after wearing prisms six months, operative means is suggested.

Assume a case is benefited, reduce prism power according to rule; ¼D prism for each degree of imbalance.