FIRST METHOD OF TREATMENT OPTICAL CORRECTION
The mere determination of the degree of an imbalance, or even the
diagnosis of a patient’s trouble, is not sufficient. If relief is to be
secured, something more must be accomplished.
As previously stated, muscular imbalance may be corrected through
one of the four following rules or methods, each explained in their
relative order:
1—Optical Correction
2—Muscular Exercise
3—Use of Prism Lenses
4—Operative Methods
ESOPHORIA
To correct a case of muscular imbalance, where six degrees of esophoria
has been determined, the first rule of making the test for optical
correction with the Ski-optometer’s spherical and cylindrical lenses,
would be in the line of routine. The binocular test made with the
phorometer and combined use of the red Maddox rod would have determined
the six degrees of esophoria.
The reason for making the binocular muscle test before and after the
optical correction is because an imbalance is often aggravated or
benefited by the correcting lenses. The optical correction frequently
eliminates the need for further muscular treatment.
For example, we will assume that the optical correction tends to
decrease the degree of esophoria from six degrees to four degrees.
According to the previously mentioned rule for correcting cases
exceeding one degree in hyperphoria, three degrees in exophoria and
five degrees in esophoria, the condition would indicate that of being
“left alone.” Just what is taking place should be fully understood—its
cause as well as its effect.
[Illustration: Fig. 25—Comparative diagram showing how a decentered
lens before a centered eye has the same effect as a centered lens
before a decentered eye.]
When not otherwise specified, accurately centered lenses are of primary
importance. The pupil of the eye should be directly behind the center
of each lens (Fig. 25).
Figure “A” of the latter sketch illustrates a perfectly centered
lens—its center indicated by a cross, the circle representing an eye
directly behind it. Figure “B” illustrates a perfectly centered pupil
behind a prism, with its center designated by a cross. To ascertain
how the centered spherical lens takes the place of a prism, Figure “C”
should be compared with Figure “B”; this will show that the eye is
decentered, while the lens is centered. A further comparison will prove
that the results in Figures “B” and “C” are identical, the correcting
lenses having practically the same effect through the decentration
of the eye as if a prism were prescribed, nature supplying its own
decentration.
TREATMENT FOR CORRECTING ESOPHORIA IN CHILDREN
In case of esophoria, regardless of amount, slightly increased
spherical power is frequently prescribed for children. This will
naturally blur or fog the patient’s vision, but in their effort to
overcome the blur, accommodation is relaxed, usually tending to correct
the muscular defect.
In such cases, as a rule, a quarter diopter increased spherical
strength may frequently be added for each degree of esophoria as
determined before the optical correction was made. In a case of 6
degrees of esophoria, the refractionist may prescribe +1.50 diopter
spherical added to the optical correction, which, let us assume, is
+1.00 sph. = -1.00 cyl. ax. 180°, so that the treatment glasses would
be +2.50 sph. = -1.00 ax. 180° (See Procedure on Page 74).
At the end of each three months’ period, the patient should be
requested to return, when the binocular and the duction test should
again be made, comparing results with the work previously accomplished.
An improvement tending to build up the left weak externus will
possibly permit of a decrease of the excessive spherical power, so
that excessive spherical power is reduced until completely removed, in
all probability overcoming the muscular defect. Esophoria is almost
invariably a false condition and frequently is outgrown under this
treatment as the child advances in years. On the other hand, esophoria
uncared for in the child may tend to produce exophoria in the adult.
HOW OPTICAL CORRECTION TENDS TO DECREASE 6° ESOPHORIA IN A CHILD
[Illustration: Assume binocular muscle test made before optical
correction shows
6° Esophoria.
+1. Sph. = -1. Cyl. Ax. 180.]
Next, locate faulty muscle by making a duction test, which
shows how abduction of left eye is made to equal that of
right eye, change being made quarterly with treatment
lenses in accordance with following rule. Note as abduction
is increased, esophoria is reduced.
Rule—prescribe a quarter diopter increased sphere for each
degree of imbalance or 0.25 × 6 equals:
+1.50 added to optical correction.
1/1/19 (assumed date) prescribed treatment lenses equal:
+2.50 = -1. × 180°.
4/1/19 (3 months later) assuming abduction has increased from
2° to 3° showing difference of 5 Es. or 0.25 × 5. equals
+1.25 added to optical correction, prescribed treatment
lenses equal:
+2.25 = -1. × 180.
7/1/19 (3 months later), assuming abduction has increased
from 3° to 4° showing difference of 4° Es. or 0.25 × 4
equals +1.00 which added to optical correction would make
prescribed treatment lenses equal:
+2.00 = -1. × 180.
And so on, every three months treatment lenses are prescribed
until both right and left eye show 8° of abduction. In this
way the treatment lenses are reduced to original correction
of +1.00 = -100 × 180. This would have required six changes
of lenses, three months apart—thus consuming 18 months time.