amount to give a modest additional base-in effect to help patients with convergence insufficiency.
Chapter Exercises
Questions
3.1.Which of the following represents a Jackson cross cylinder?
a.–2.00 +4.00 × 180
b.–1.00 +3.00 × 90
c.+2.00 +3.00 × 180
d.+1.00 –1.00 × 90
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3.2.When performing cycloplegic retinoscopy on an anxious 7-year-old boy, you notice that the central reflex shows with movement while the peripheral reflex shows against movement. What is the most likely cause?
a.keratoconus
b.congenital cataract
c.spherical aberration
d.insufficient time for maximum cycloplegia
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3.3.What type of distortion is shown in Figure 3-38?
a.pincushion distortion
b.barrel distortion
c.image jump
d.image displacement
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3.4. A patient with +9.00 D spectacle lenses (vertex distance is 12 mm) requires a new spectacle frame because of recent nasal surgery. The vertex distance of the new frame is required to be 22 mm to avoid any nasal discomfort. What power is required for the new spectacles?
a.+7.25 D
b.+8.25 D
c.+9.25 D
d.+10.25 D
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3.5. On the basis of the type of spectacle lenses shown in Figure 3-39, what is the patient’s probable occupation?
a.retired investment banker or stockbroker
b.professional senior golfer
c.airline pilot
d.jewelry or watch-repair technician
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3.6.The Abbe number is a measure of
a.spherical aberration
b.chromatic aberration
c.image displacement in plus lenses
d.curvature of spectacle lenses
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3.7.Your refraction determines that a –8.00 D lens in a trial frame with a vertex distance of 10 mm from the patient’s cornea provides 20/15 visual acuity. What is the minus-power lens needed if the patient requires a vertex distance of 14 mm to use her favorite existing spectacle frame?
a.–7.25 D
b.–8.25 D
c.–9.25 D
d.–10.25 D
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3.8. The primary reason that patients with presbyopia cannot tolerate significant anisometropia in bifocal lenses is
a.asthenopia
b.inability of the lens to accommodate and correct any hyperopic error
c.reduced vertical fusion amplitude
d.spherical aberration
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3.9.In bifocal lens design, image jump may be minimized by
a.placing the optical center of the segment as close as possible to the top of the segment
b.placing the top of the segment as close as possible to the distance optical center
c.using a smaller bifocal segment
d.using a blended bifocal segment that has no visible line of separation
e.lowering the bifocal segment by 3 mm