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Pubmed for Handhelds

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  • Title: Spectacle correction for aphakia. The prismatic effect.
    Author: Fonda G.
    Journal: Surv Ophthalmol; 1981; 26(3):154-6. PubMed ID: 7336328.
    Abstract:
    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.
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