Chapter XIIA CONDENSATION OF PREVIOUS CHAPTERSON THE PROCEDURE FOR MUSCLE TESTINGWITH THE SKI-OPTOMETER
Thepresent 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-optometerconstantly 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—
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 thefirstmethod of treatment. This requires a thorough reading ofChapter IXon Treatment for Correcting Esophoria in Children and a careful study of the formula. For synopsis seePage 74.
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°). Exerciseto 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).
EmployThird Method—Use of Prisms for Constant Wear to effect treatment.
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.
This work being of a technical nature, it is deemed best for the reader to study ChapterXIIIandXIV.