Concepts of Optics Quiz. 8. Spherical lenses focus along a single point; cylindrical lenses focus along a.

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1 Concepts of Optics Quiz 1. Prisms bend light from (apex/base) to (apex/base). 2. Prisms displace images in the direction of the (apex/base). 3. A (plus/minus) lens is convex. 4. A (plus/minus) lens diverges rays of light. 5. A (plus/minus) lens minifies the face behind it. 6. Focal power is given in what units? 7. Focal length is given in what units? 8. Spherical lenses focus along a single point; cylindrical lenses focus along a 9. How do you transpose from plus to minus cylinder forms? 10. The spherical equivalent of a spherocylinder lens is determined by the equation _ 11. A standard single vision lens ready to be edged is called a 12. A lens with only one surface ground is called a _ 13. The base curve of a spherical or minus cylinder lens is its curve. 14. The base curve of a plus cylinder lens is its curve. 15. The assumed average vertex distance is. 16. What is Prentice s Rule? 17. In a plus lens, the base of a prism and the direction of decentration are the 18. In a minus lens, the base of a prism and the direction of decentration are the 19. On the right eye, a prism whose base is pointed in a nasal direction would be called base 20. On the left eye, a prism whose base is pointed in a temporal direction would be called base 21. One prism diopter means a ray of light is displaced over a distance of 22. An Abbe value quantifies (longitudinal/lateral) _

2 23. A lens has a central region of high power called the inside a region of little to no power called the 24. The distance from the top of a segment to the bottom of a segment is called 25. Is seg height measured from the top of the segment to the bottom of the frame at the center of the segment or the bottom of the frame at its lowest point? 26. The total inset is a combination of and 27. What is image jump? 28. The and the together make up the fitting cross. 29. For every diopter of prism, the fitting cross should move in the (same/opposite) direction as the prism. 30. A difference in power between eyes is called The difference between image sizes seen by such eyes is called The difference between prismatic effects seen by such eyes is called 31. When an anisometropic wearer switches to multifocals, beware of Some need this issue corrected using 32. The location of the wearer s pupil on the lens is called the (optical center/major reference point). 33. When a wearer has no prescribed prism, the optical center and major reference point of their lenses is (the same/different). 34. When a wearer has prescribed prism, the optical center and major reference point of their lenses is (the same/different). 35. A PD measurement of R32/L35 mm is called (monocular/binocular); a PD measurement of 66 mm is called (monocular/binocular). 36. A lens has a convex front surface and a concave back surface. 37. % cylinder power is in effect at the specified axis, while % cylinder power is in effect 90 degrees from the specified axis. 38. Axis is a notation of (power/position). 39. A blended bifocal will have a segment embedded within it. 40. A flat top segment is named by 41. A segment that looks like a flat-top but has a curve to its top edge is called or 42. A ribbon B seg is (taller/shorter) than a ribbon R seg.

3 43. A segment that takes up the entire bottom portion of a lens is called or 44. A plumber or other presbyope who does detail work above their eyeline might use a multi-segment lens called a 45. A lens that is primarily a reading lens, but has a round distance segment near the top of the lens, is called a 46. A higher Abbe value means there is (more/less) chromatic aberration. 47. Measuring PDs should be done with the dispenser sitting cm or inches from the wearer. 48. Every degrees of pantoscopic tilt will effectively move the optical center of the lens (up/down) one millimeter, but will slightly (increase/decrease) the lens spherical power and its cylinder power along the (90/180) degree axis. 49. Possible reasons a multifocal wearer might need a lower-than-usual seg height include: posture that carries the head unusually far (back/down), height that is very (tall/short), and an occupation that is more (indoor and office oriented/outdoor and distance oriented). 50. The fitting cross for children in progressives should be (2/4) mm (higher/lower) than normal; the seg line of bifocals should (bisect the child s pupils/be fit normally). 51. OD stands for and indicates the (right/left) eye. 52. OS stands for and indicates the (right/left) eye. 53. stands for and indicates both eyes. 54. Reducing vertex distance (decreases/increases) the effective power of a plus lens, and (decreases/increases) the effective power of a minus lens. 55. The angle at which a prism refracts light is equal to the angle of its 56. Prism by decentration creates a (thicker/thinner) lens than ground-in prism. 57. Plus lenses cause (magnification/minification) with a (pincushion/barrel) effect while minus lenses cause (magnification/minification) with a (pincushion/barrel) effect. 58. The power and prism changes caused by pantoscopic tilt are (easier/harder) to deal with than those caused by wrap. 59. Wrap will slightly (increase/decrease) a lens pair s spherical power and cylinder power along the (90/180) degree axis, and will induce prisms that are the (same/opposite) base in the right and left eyes. 60. It is impossible to create prism by decentration with lenses, but they are thinner than similar spherical lenses. 61. Intermediate vision is defined as vision at to inches.

4 62. To find the optical center of a flat-top bifocal, subtract (the seg drop/the seg width/one-half the seg width) from the (seg depth/seg width/seg height). 63. Image jump will always be base 64. Most people with anisometropia tolerate, the difference in prismatic effects between differently-powered lenses, better in the (vertical/horizontal) dimension than the (vertical/horizontal). 65. A lens is ordered for an un-seeing eye and the prescription may be used for cosmetic effects. 66. A lens is prescribed at a 12 mm vertex distance. Will the lens effectie power be stronger or weaker if a frame is chosen with 15 mm vertex distance? 67. Name two ways of describing a base-down prism using the degree system. 68. A left-lens prism whose base faces a wearer s left temple would be described as oriented degrees. 69. A right-lens prism whose base faces a wearer s right temple would be described as oriented degrees. 70. A right-lens prism whose base faces the wearer s nose would be described as oriented degrees.

5 Concepts of Optics Answers 1. apex, base 2. apex 3. plus 4. minus 5. minus 6. diopters, D 7. meters 8. meridian 9. Algebraically add the sphere plus the cylinder to find the new sphere; change the sign of the cylinder; change the axis by 90 degrees 10. Sph + Cyl/2 11. lens blank or finished lens 12. semifinished lens 13. front 14. weakest front mm 16. Prism diopters = centimeters of decentration * absolute value of lens power 17. same 18. opposite 19. in 20. out cm, 1 m 22. longitudinal, chromatic aberration 23. lenticular, aperture, carrier 24. seg depth 25. the bottom of the frame at its lowest point 26. seg inset, distance decentration 27. The displacement of an image when a wearer s gaze crosses the bifocal line as a prismatic effect is induced. 28. PD and pupil height , opposite 30. anisometropia, aniseikonia, anisophoria 31. vertical imbalance; slab off or bicentric grind 32. MRP 33. the same 34. different 35. monocular, binocular 36. meniscus 37. zero, position 39. round 40. its width at the top of its segment in millimeters 41. curve-top or PanOptik 42. shorter

6 43. Franklin or Executive 44. double-d 45. Rede-Rite or minus-add upcurve 46. less , two, down, increase, back, tall, outdoor or distance oriented 50. 4, higher, bisect the child s pupils 51. right 52. left 53. OU, oculus uterque 54. decreases, increases 55. apex 56. thicker 57. magnification, pincushion, minification, barrel 58. harder 59. increase, 90, opposite 60. aspheric , one-half the seg width, the seg height 63. base down 64. anisophoria, horizontal, vertical 65. balance 66. weaker degrees, 90 degrees base down