Math of Optics Quiz. 6. A lens has power x090 and will use minus cylinder form. What curves will beground if the base curve is +5.00?

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1 Math of Optics Quiz 1. A lens has focal length 20 cm behind the lens. What is its power? 2. A lens has power diopters. What is its focal length? 3. A lens has front power and back powers of at 90 degrees and at 180 degrees. What form is the lens and what is its nominal power? 4. A lens has front power at 90 degrees and at 180 degrees; its back power is What form is the lens and what is its nominal power? 5. Transpose this prescription: x A lens has power x090 and will use minus cylinder form. What curves will beground if the base curve is +5.00? 7. A prism displaces light 9 cm when the light source is 300 cm from the prism. What is the prism s power? 8. A lens is decentered 3 mm toward the wearer s nose. What prism effect is induced? 9. A patient wears lenses and has a PD of 60 mm. If lenses are incorrectly made with a PD of 64 mm, what prism effect is induced? 10. A patient wears lenses which are decentered 3 mm out and 4 mm up. What prism effect is induced? 11. On the left eye, a patient wears a PL x090 lens decentered 5 mm up and 2 mm out. What prism is induced?

2 12. A patient wears x090 lenses decentered 7 mm out and 2 mm up. What prismatic effects are induced? 13. A patient has prescription OD x180, OS x180, ADD What prescription should you order for reading glasses? 14. A patient has prescription OD x170, OS x170, ADD What prescription should you order for computer/reading bifocals? 15. How much image jump does a mm round segment create? 16. How much image jump does a flat-top seg (width 25 mm, depth 17.5 mm) create? 17. A prescription reads OD x180 3 BU, OS x180 3ΔBD. The measured pupil height is 27 mm in both eyes. What fitting cross heights should be ordered? 18. A prescription reads OD x180 5ΔBI, OS x180 5ΔBI. The measured PDs are R29.5 mm, L 30 mm. What fitting cross PDs should be ordered? 19. A wearer looks 4mm below the edge of 22mm round bifocals at power. How much vertical prism is induced? 20. A wearer looks 4 mm below the seg line of bifocals where the OC is on the seg line and the seg power is How much vertical prism is induced? 21. How much slab off prism on which lens would correct vertical imbalance at 10 mm below the distance OC of prescription OD +2.75, OS -2.75? 22. The wearer s PD is 62 mm. The chosen frame has an A measurement of 48 mm and a DBL of 20 mm. What decentration is required?

3 23. A progressive lens is ordered with prescription OD x070, OS x110, ADD The wearer s monocular PDs are R33mm/L31mm, and OC heights are R25/L23. The frame has measurements A 50mm, B 40 mm, and DBL 20 mm. How much horizontal decentration and MRP raise or drop is needed for each lens? 24. Light rays pass through a lens and converge at a point 50 cm behind the lens. What is the lens power? 25. A lens has what prismatic effect 8 mm below the optical center? 26. A PD is mistakenly ordered as 70 mm when it should be 66 mm. What prism would be found if the distance prescription is OU ? 27. Transpose the following prescription to minus cylinder form: x Using the prescription x045, what is the power of the lens at the 90 th meridian? 29. Using the prescription x090, what is the power of the lens at the 180 th meridian? 30. According to the Vogel formula, what is the best base curve for a lens? 31. The spherical equivalent of a x090 lens is. 32. A lens with prescription x045 has what power at the 90 th meridian? 33. If a +10 lens is moved 5 mm nearer the eye, it will be (stronger/weaker) by about (.25D/.5D).

4 34. A lens has power x180 and will be ground in plus cylinder form. What curves will this lens have if the base curve is +6.00? 35. How much slab off prism in which lens will correct the vertical imbalance induced for a patient with prescription OD -5.75, OS -1.25, ADD who reads at a distance 5 mm below the seg line of a 50 mm tall frame with a seg height at 20 mm? 36. How much slab off prism in which lens will correct the vertical imbalance for a patient with prescription OD x045, OS x045, ADD +1.00, who has a distance OC at 20 mm and reads at a distance 1 mm below the seg line of a seg with height at 16 mm? 37. A progressive lens is ordered with prescription OU x070 ADD The patient s monocular PDs are R33mm/L31mm and their near PDs are R31/L29.5. The frame has measurements A50, B40, DBL20. How much distance decentration, seg inset, and total inset is needed for each lens?

5 Math of Optics Answers D cm (40 cm in front of the lens) 3. minus cylinder form, PL x plus cylinder form, x x Front curve remains +5.00, back curves at 90 degrees, at 180 degrees base in 9. 1 base in base in, 2.4 base down base out base out, 0.6 base up 13. OD x180, OS x OD x170, OS x170, ADD base down base down mm for the right eye, 28 mm for the left mm for the right eye, 31.5 mm for the left base down base up base up on the left lens mm inward 23. For the right eye: 2 mm inward decentration, 5 mm MRP raise. For the left eye: 4 mm inward decentration, 3 mm MRP raise D base up base in for each eye x PL (0.00D) 33. weaker,.5d 34. Back curve is -5.00, front curves at 90 degrees, at 180 degrees base up on right lens base up on left lens 37. Right distance decentration 2 mm, seg inset 2 mm, total inset 4 mm; left distance decentration 4 mm, seg inset 1.5 mm, total inset 5.5 mm