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4.1. Which prescription represents a Jackson cross cylinder?
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−2.00 +4.00 × 180
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−1.00 +3.00 × 90
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+2.00 +3.00 × 180
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+1.00 −1.00 × 90
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4.2. 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?
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keratoconus
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congenital cataract
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spherical aberration
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insufficient time for maximum cycloplegia
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4.3. What type of distortion is shown in Figure 4-38
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pincushion distortion
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barrel distortion
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image jump
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image displacement
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4.4. 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?
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+7.25 D
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+8.25 D
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+9.25 D
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+10.25 D
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4.5. Based on the type of spectacle lenses shown in Figure 4-39, what is the patient’s probable occupation?
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retired investment banker or stockbroker
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professional senior golfer
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airline pilot
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jewelry or watch-repair technician
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4.6. The Abbe number is a measure of what characteristic?
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spherical aberration
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chromatic aberration
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image displacement in plus lenses
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curvature of spectacle lenses
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4.7. 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?
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−7.25 D
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−8.25 D
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−9.25 D
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−10.25 D
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4.8. What is the primary reason that patients with presbyopia cannot tolerate significant anisometropia in bifocal lenses?
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asthenopia
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inability of the lens to accommodate and correct any hyperopic error
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reduced vertical fusion amplitude
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spherical aberration
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4.9. In bifocal lens design, image jump may be minimized by which step?
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placing the optical center of the segment as close as possible to the top of the segment
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placing the top of the segment as close as possible to the distance optical center
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using a smaller bifocal segment
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using a blended bifocal segment that has no visible line of separation
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lowering the bifocal segment by 3 mm
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4.10. An angle of 45° corresponds to how many prism diopters (∆)?
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45.0∆
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22.5∆
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90.0∆
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100.0∆
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4.11. Which statement applies to bifocal lenses that are prescribed for a patient with myopia?
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The practitioner should leave the choice of the segment type to the optician.
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A round-top segment is preferred because of its thin upper edge, which causes less prismatic effect.
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A flat-top segment is preferred because it lessens image jump.
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The 1-piece shape is indicated for adds greater than +2.00 D.
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A split bifocal should be used because patients with myopia do not accept bifocal lenses easily.
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4.12. An aphakic contact lens wearer (+13.00 soft contact lens in each eye) needs to switch to spectacles but finds that she experiences diplopia at near. What prismatic correction would you expect to correct her diplopia?
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base-up prism
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base-in prism
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oblique prism
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base-out prism
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4.13. A patient who has just been prescribed new progressive addition lenses returns with the complaint that he needs to tilt his chin up in order to see clearly at distance. What is the most likely source of the problem?
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add power that is too strong
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add power that is positioned too high
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undercorrected hyperopia or overcorrected myopia
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incorrect optical centers
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4.14. Following cataract surgery in the left eye, the patient has a refraction of right, −3.50 D; left, −0.50 D. You prescribe this with a +2.50 flat-top bifocal set 3 mm below the optical center of the lens. How much induced prism will there be when the patient is looking 4 mm below the top of the bifocal?
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1.2∆ base down in the right eye
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no induced prism
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0.9∆ base down in the right eye
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2.1∆ base down in the right eye