Fonda G
Surv Ophthalmol. 1981 Nov-Dec;26(3):154-6. doi: 10.1016/0039-6257(81)90064-3.
Because spectacle lenses are fixed in position relative to the eyes, the visual axes during convergence pass nasal to the optical centers, and create a prismatic effect. The eye rotates less than 25 degrees before the head is turned; therefore for central vision, only an area of the lens about 13 mm wide is used. A reading addition of +6.00 D is probably the maximal power bifocal addition that can be prescribed for comfortable binocular vision in a high plus correction. The distance correction produces a base-out effect of at least 4 delta for each eye at the reading distance, even though the bifocal segments are adequately decentered.
由于眼镜片相对于眼睛的位置是固定的，在集合过程中视轴经过光学中心的鼻侧，从而产生棱镜效应。在头部转动之前眼睛转动小于25度；因此对于中心视力，仅使用镜片约13毫米宽的区域。+6.00D的阅读附加度数可能是在高度数矫正中为获得舒适双眼视觉而能开具的最大度数双焦点附加度数。即使双焦点部分已充分移心，在阅读距离时，远用矫正对每只眼睛至少产生4棱镜度的底向外效应。
