SECOND METHOD OF TREATMENT—MUSCULAR EXERCISE
MADE WITH TWO ROTARY PRISMS AND RED MADDOX ROD
EXOPHORIA
If a case is one of exophoria of six degrees, where the second method
of treatment or muscular exercise is in line of routine, it is
essential to first determine through a duction test and the preparation
of the diagram exactly which one of the four muscles are faulty (Fig.
24).
Having determined, with the aid of the diagram, first, the existence of
6 degrees of exophoria; second, 18 degrees of adduction; third, a weak
left internus—the next procedure is to determine what degree of prism
will enable the patient to obtain single binocular vision, with both
eyes looking “straight.”
To determine this, place both of the Ski-optometer’s rotary prisms in
position with the handle of each pointing outward horizontally. The red
line or indicator of each prism should then be placed at 30° of the
outer scale (Fig. 26).
The red Maddox rod should be horizontally positioned before the eye,
the white line on indicator pointing to 180° of the scale (Fig.
27). The strength of the rotary prism before the right eye should
thereupon be reduced by rotating the prism indicator or red line toward
the upper zero (0) to a point where the patient first sees the red
streak—assuming that the red line appears at 42 degrees, that is 30
degrees before the left eye and 12 degrees before the right.
[Illustration: Fig. 26 (A and B)—First position of rotary prisms to
determine amount of prism exercise to be employed for building up the
weak muscle.]
The prism should then be still further reduced until the vertical
streak produced by the Maddox rod directly bisects the muscle testing
spot of light. Assuming that this point be thirty-eight degrees, which
is four degrees less, _single binocular vision is produced_.
[Illustration: Fig. 27—Position of red Maddox rod used in conjunction
with Fig. 26 for prism exercising.]
For example, sixty degrees of prism power (the combined power of the
two rotary prisms) will usually cause complete distortion. Therefore,
as outlined in Figure 28, the patient, seeing only out of the _right_
eye, will detect nothing but a white light. By gradually reducing the
strength of the prism before the right, which is the good eye, the
patient will eventually see a red streak off to the left. A continued
and gradual reduction to a point where the red streak bisects the white
light, will determine how much prism power is required for the patient
to obtain single binocular vision, thus establishing the same image at
the same time on each fovea or retina (Fig. 20).
This has taught the patient to do that which he has never before
accomplished. Therefore, after having been taught how to make the two
eyes work in relation to each other, the natural tendency thereafter
will be to strive for the same relationship of vision with both eyes.
The refractionist should then aim to reduce the excessive amount of
prism required to give binocular vision, which can be accomplished by
muscular exercise.
It must always be remembered before the refractionist is ready to
employ the muscular exercise or second method, that the degree of prism
required to give the patient single binocular vision must be determined
with the optical correction in place. The exercise must be practised
daily in routine, a daily record being essential.
AN ASSUMED CASE
We will assume a case where 42 degrees is required to enable the
patient to first see the red streak as produced by the Maddox rod to
the extreme left. Through a continued gradual reduction of 4 degrees
(or to 38 degrees), we next learn that the streak was carried over
until it bisected the white spot of light, giving single binocular
vision and producing a position of rest.
[Illustration: Fig. 28—Simplified chart showing the prism action
employed in developing a weak ocular muscle through alternating prism
exercise. Either side of 38° in excess of 4° causing diplopia.]
The patient has now established the limitation of the exercise, which
is four degrees, this limitation being determined by the difference
between the point where the streak was first seen to the extreme side
and where it bisected the spot. The same amount of four degrees should
then be used for the opposite side, thus reducing the prism strength to
34 degrees.
This again produces diplopia, because of the lesser amount of prism
power employed to give single binocular vision. The refractionist
should then return to 38 degrees, where single binocular vision had
originally been determined (Fig. 28), alternating back to 42, returning
to 38, over to 34, back to 38, and so on. This procedure should be
employed once a day just after meals for about five minutes, and
repeated ten times, constantly striving for a slight reduction of prism
power from day to day.
EFFECT OF MUSCULAR EXERCISE
This muscular treatment, or constructive exercising, should enable the
patient to overcome his amount of four degrees in either direction in
about a week. Hence in the case showing 38 degrees for single binocular
vision, results may be looked for in about nine weeks—four degrees
divided into 38 degrees. While the patient is undergoing the treatment,
which is nothing more than the strengthening of the interni muscles
or developing adduction, it is natural to believe that the amount of
imbalance is likewise being conquered. This, however, is readily
determined from time to time by making the binocular muscle test with
the phorometer and Maddox rod, as well as the duction chart test (Fig.
24), as previously outlined.
To fully appreciate the effect of this muscular treatment, the reader
need only hold his head in a stationary position, casting his eyes
several times from the extreme right to the extreme left, not failing
to note the apparent muscular strain. On the other hand, with the
aid of the Ski-optometer’s rotating prisms, the refractionist not
only has complete control of the patient’s muscles at all times, but
scientifically accomplishes muscular exercise without any tiresome
strain, overcoming all possible exertion.
After the case in question has been reduced to 30 degrees, having no
further use for the rotary prism, it may be removed from before the
right eye and the same exercising procedure continued as before with
the remaining left side rotary prism by reducing its power, until it is
likewise down to zero.
Having reduced both prisms to zero, each prism should again be placed
in position with zero graduations vertical and the prism indicator on
upper zero. Both prisms should then be turned simultaneously about
four degrees toward the nasal side of the patient, thus tending to
jointly force corresponding muscles of both eyes.
HOME TREATMENT FOR MUSCULAR EXERCISE—SQUARE PRISM SET USED IN
CONJUNCTION WITH THE SKI-OPTOMETER
Where a patient is unable to call each day for this muscular treatment
or exercise, the work will be greatly facilitated by employing a
specially designed set of square prisms ranging in strength from ½ to
20 degrees for home treatment. As in the case previously cited, it is
necessary to carefully instruct the patient that the interni muscles
_must_ be developed, hence prism base _out_ with apex in must be
employed. Attention should then be directed to a candle light, serving
as a muscle testing spot of light and stationed in a semi-dark room at
an approximate distance of twenty feet.
Having determined through the Ski-optometer the strength of the prism
required after each office treatment, its equivalent should then be
placed in a special square prism trial-frame which permits rotation of
the prism, although the patient is frequently taught to twirl the lens
before the eye. This exercise may be continued for about five minutes
each day.
The patient should also be instructed to call at the end of each week,
when the work may be checked by means of the Ski-optometer’s rotary
prisms, making the duction test as previously explained and outlined in
Fig. 24. It is then possible to determine whether or not satisfactory
results are being obtained. Otherwise the exercise should be abandoned.
Should the second method employed in the work of muscular imbalance not
prove effective, the third method requiring the use of prisms would be
next in routine.