Chapter XSECOND METHOD OF TREATMENT—MUSCULAR EXERCISE

Made With Two Rotary Prismsand Red Maddox Rod

If acase 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.

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 testingspot of light. Assuming that this point be thirty-eight degrees, which is four degrees less,single binocular vision is produced.

Fig. 27—Position of red Maddox rod used in conjunction withFig. 26for 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 inFigure 28, the patient, seeing only out of therighteye, 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 thesame 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.

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 overuntil it bisected the white spot of light, giving single binocular vision and producing a position of rest.

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 shouldthen 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.

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 readilydetermined 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 fourdegrees toward the nasal side of the patient, thus tending to jointly force corresponding muscles of both eyes.

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 musclesmustbe developed, hence prism baseoutwith 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 inFig. 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.

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