. Refraction and how to refract : including sections on optics, retinoscopy, the fitting of spectacles and eye-glasses, 274 REFRACTION AND HOW TO REFRACT. however, more expensive than the cement form ; but, likethe Frankhn, it often looks clumsy or heavy on accountof the frame. Perfection or Morck bifocal must besignified in writing the prescription. 3. Cement Bifocals (see Figs. 165 and 166).—This isthe most common form of bifocal and the least expensivein its original cost, as also when making changes in thenear correction. This bifocal is made by cementing a seg-. FiG. 165. Fig. 166.
. Refraction and how to refract : including sections on optics, retinoscopy, the fitting of spectacles and eye-glasses, 274 REFRACTION AND HOW TO REFRACT. however, more expensive than the cement form ; but, likethe Frankhn, it often looks clumsy or heavy on accountof the frame. Perfection or Morck bifocal must besignified in writing the prescription. 3. Cement Bifocals (see Figs. 165 and 166).—This isthe most common form of bifocal and the least expensivein its original cost, as also when making changes in thenear correction. This bifocal is made by cementing a seg-. FiG. 165. Fig. 166. Fig. 167.
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