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.