. Refraction and muscular imbalance, as simplified through the use of the ski-optometer. e, whilethe patients attention should be directed, W\\hboth eyes open, to the largest letter on thedistant test chart; or if preferable, the Greekcross in the Woolf opthalmic chimney may beused. Either one, however, should be locatedon a plane with the patients head. As a guidefor the operator, it might be well to rememberthat when the handle of the rotary prism is ina horizontal position, the lateral or horizontalmuscles are being tested. On the other hand,when the handle is in a vertical position, thever
. Refraction and muscular imbalance, as simplified through the use of the ski-optometer. e, whilethe patients attention should be directed, W\\hboth eyes open, to the largest letter on thedistant test chart; or if preferable, the Greekcross in the Woolf opthalmic chimney may beused. Either one, however, should be locatedon a plane with the patients head. As a guidefor the operator, it might be well to rememberthat when the handle of the rotary prism is ina horizontal position, the lateral or horizontalmuscles are being tested. On the other hand,when the handle is in a vertical position, thevertical muscles are undergoing the test. Adduction Adduction, or relative convergence, is thepower of the internal muscles to turn the eyesinward; prism power base out and apex m,is employed. To test adduction of the patients right eye,the rotary prism should be placed in positionbefore the right eye, the red line or prism in-dicator being registered at zero upon theprism upper scale. The two cyphers (0)should be placed in a vertical position with [59] Refraction and Muscular Imbalance. Fig. 22—To test adduction, base out is required. Rotaryprisms line or indicator should be rotated from zero out-wardly. To test abduction, base in is required. Indi-cator should be rotated inwardly from zero. the handle pointed horizontally (Fig. 21).The rotary prism should then be rotated sothat its red line or indicator is rotated out-ward from zero until the large letter—pre-ferably the largest letter, which is usually E—on the distance test-type or the Greek crosspreviously referred to, first appears to doublein the horizontal plane. The readingon the scale of measurements should ac-cordingly be noted. This test should be re-peated several times, constantly striving forthe highest prism power that the patient willaccept without producing diplopia. Theprism equivalent thus obtained will indicate [60] Refraction and Muscular Imbalance the right adduction and should be so re-corded, as desi
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