A CONDENSATION OF PREVIOUS CHAPTERS ON THE PROCEDURE FOR MUSCLE TESTING
WITH THE SKI-OPTOMETER
The present chapter, intended for those desiring a synopsis or
condensed summary of muscular imbalance work, should prove of the
utmost assistance to the busy refractionist. Muscular imbalance work
can be successfully conducted if the following routine is studied and
memorized, with the Ski-optometer _constantly before the reader_.
The chapters containing the corresponding figures and diagrams or
illustrations will then be readily comprehended. It is also important
to carefully note the captions under each diagram.
1. Without any testing lenses before patient’s eyes, direct attention
to a 20-foot distant muscle testing spot of light (Fig. 9).
2. Place phorometer handle vertically (Fig. 16).
Place red Maddox rod vertically (Fig. 15). Patient should see a white
spot of light, and a red horizontal streak (Fig. 17).
Simply turn phorometer handle until horizontal streak bisects white
spot of light. Pointer then indicates amount of deviation on red
scale. Ignore cases less than 1° hyperphoria, whether right or left
designated by (R. H.—L. H.).
3. Place phorometer handle horizontally (Fig. 19).
Place red Maddox rod horizontally (Fig. 18). Patient should see a white
spot of light and a vertical red streak (Fig. 20).
Simply turn phorometer handle until red streak bisects spot of light.
Pointer indicates amount of deviation on white scale, whether esophoria
or exophoria designated by (Es—Ex).
4. Ignore all exophoria cases, less than 3°.
Ignore all esophoria cases, less than 5°—except in children, ignore
less than 3° of esophoria.
5. Always make the above or binocular muscle test—with phorometer
and red Maddox before optical correction or (test for spheres and
cylinders) and again after optical correction where case shows more
than 1-3-5 rule, to determine whether muscles are aggravated or
benefited.
6. In cases showing more than the 1-3-5 rule, shown in above No. 4,
make monocular duction test first with rotary prism before patient’s
right eye,—then with rotary prism before left eye to find faulty muscle
and determine which eye is affected.
7. To test adduction, prism base out is required. Rotary prism’s red
line or indicator should be rotated from zero outwardly. To test
abduction, base in is required. Indicator should be rotated inwardly
from zero (Fig. 22). Power of adduction as compared with abduction, is
normally 3 to 1—usually rated 24 to 8.
8. To test superduction, base down is required. Rotary prism’s line or
indicator should be rotated downward from zero. To test subduction,
base up is required. Indicator should be rotated upward from zero.
Power of superduction as compared with subduction, is normally
equal—usually rated 2 for each (Fig. 23).
9. Direct patient’s attention to largest letter on distant chart,
usually letter “E,” rotating red line indicator of rotary prism
outlined in above No. 7 and No. 8, until diplopia is first procured.
10. The use of a duction chart on a record card, quickly designates
pull for each of four muscles (Fig. 24), illustrating an assumed case
of—
1st—6D of Exophoria.
2nd—18° adduction (which must be developed to 24°).
3rd—Patient has a left weak internus.
11. Employ First Method—Optical Correction—to effect treatment.
12. Assuming a case of a child with 6° of esophoria—8° of right
abduction and 2° left abduction indicating a left weak externus,
prescribe a quarter diopter increased plus spherical power for
each degree of imbalance, thus adding +1.50D spherical to optical
correction. This is the _first_ method of treatment. This requires a
thorough reading of Chapter IX on Treatment for Correcting Esophoria in
Children and a careful study of the formula. For synopsis see Page 74.
FOUR METHODS OF TREATING AN IMBALANCE CASE WHEN THE PRECEDING ONE FAILS
1st—Optical correction;
2nd—Muscular exercise or treatment;
75% ARE CURABLE WITH FIRST AND SECOND METHODS.
3rd—Prisms;
5% ARE CURABLE WITH THIRD METHOD.
4th—Operation;
20% ARE CURABLE WITH FOURTH METHOD.
13. When first method of treatment fails, EMPLOY SECOND METHOD—Muscular
Exercise—to effect treatment.
1st—Find degree of prism patient will accept to produce single
binocular vision with optical correction on, placing both rotary prisms
in position, handles horizontal, red line on 30° of temporal scale of
each, giving total value to 60° (Fig. 26a and b).
2nd—Also place red Maddox rod before patient’s eye (rods horizontal)
(Fig. 18), calling patient’s attention to usual muscle testing spot of
light.
3rd—Reduce prism before good eye until red streak appears, noting
degree (which we assume shows 42° the combined total value of both
prisms) slowly continue to decrease prism until streak bisects spot.
Assume this shows total of 38°. Either side of 38° in excess of 4° (38
to 42) produces diplopia. Prisms must only be rotated from 38° to 42°
back to 38° over to 34°—back to 38° over to 42°—back again to 38° and
so on—exercise to be continued daily ten times for five minutes (Fig.
28).
4th—At end of each week, duction test should again be made. Duction
chart should show a tendency to reduce exophoria by a gradual building
up of adduction, approximately one week is usually sufficient to teach
patient to hold streak within the spot (between 38° and 42°). Exercise
to be continued until both prisms are worked down to zero. Exercise
tends to teach patient how to establish same image on each fovea or
retina at same time.
5th—If patient is unable to call daily for treatment, employ home
treatment. (Read “Home Treatment for Muscular Exercising,” Page 82).
Employ THIRD METHOD—Use of Prisms for Constant Wear to effect treatment.
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.
CYCLOPHORIA
This work being of a technical nature, it is deemed best for the reader
to study Chapter XIII and XIV.