CH 5 Ophthalmic Lenses

• What three characteristics must be considered in the design of an ophthalmic lens?

  1) Thickness

  2) Chromatic Aberration

  3) Weight
• A manufacturing standard established by the American National Standards Institute (ANSI) for glass lenses is:

  
  

  a) The lens must be scratch resistant

  
  

  b) The lens must have a refractive index of 1.5230

  
  

  c) The lens must be heat or chemically tempered

  
  

  d) Patients must be told that glass lenses are heavy and uncomfortable

  c) The lens must be heat or chemically tempered
• What are some advantages of CR-39 lenses over glass lenses?

  1) CR-39 lenses are lighter

  2) They do not fog as easily

  3) Tinting is more uniform and can be manipulated

  4) Produce less glare and internal reflections

  5) Improve visual performances
• What are some advantages of glass lenses over CR-39 lenses?

  1) Glass lenses do not scratch as easily

  2) They are thinner because the index of refraction is higher

  3) They do not warp as easily as CR-39 lenses
• Why is polycarbonate a good choice of lens material for children and monocular patients?

  
  

  a) Polycarbonate is more impact-resistant than crown glass and CR-39

  
  

  b) Polycarbonate is 10% thinner than crown glass and 15% thinner than CR-39

  
  

  c) Polycarbonate is the most scratch-resistant lens material

  
  

  d) Polycarbonate filters 99% of UV rays naturally

  a) Polycarbonate is more impact-resistant than crown glass and CR-39
• What is the material used to make high-index plastic lenses?

  
  

  a) CR-39

  
  

  b) Polyurethane

  
  

  c) Polycarbonate

  
  

  d) Abbé

  b) Polyurethane
• What four factors must be considered in order to dispense the thinnest lens possible?

  1) Frame size

  2) Lens Material

  3) Aspheric design

  4) Center thickness
• What is the ANSI standard for drop-ball testing in dress eyewear?

  Lenses designed for dress eyewear must withstand the impact of a 5/8 inch steel ball dropped from a height of 50 inches.
• What is the ANSI standard for drop-ball testing for industrial safety lenses?

  Lenses designed for safety wear must withstand the impact of a 1 inch steel ball dropped from a height of 50 inches.
• What other standard, in addition to drop-ball testing, applies to industrial safety lenses?

  Safety lenses must have a minimum thickness of 3.0mm.
• True or False: "Polycarbonate, high-index plastic and CR-39 lenses do not have to routinely tested in the lab by the drop-ball test."


  True
• What are two methods of treating glass lenses for impact resistance?

  1) Heat tampering

  2) Chemical tampering
• What type of PD (pupillary distance) is measured when fitting progressive additional lenses (PAL)?

  Monocular
• When dispensing a pair of progressive additional lenses (PAL), the manufacturer's markings

  
  

  a) Should be cleaned off so the patient can test for clarity

  
  

  b) Need to be left on to verify the type of lens ordered

  
  

  c) Will help the dispenser make the final frame adjustments

  
  

  d) Will show the patient how the lenses should be used

  c) Will help the dispenser make the final frame adjustments
• What is an identifying factor of an executive or Franklin bifocal?

  
  

  a) A large ridge that runs across the entire width of the lens.

  
  

  b) They are available in both glass and plastic.

  
  

  c) It has a very nice cosmetic appeal.

  
  

  d) They fit more securely in the frame eyewear than other lens styles.

  a) A large ridge that runs across the entire width of the lens.
• What is the most likely intermediate power if the near power is +3.00?

  
  

  a) +3.00

  
  

  b) +2.00

  
  

  c) +1.00

  
  

  d) +1.50

  d) +1.50
• A nurse states she has to tilt her head back to read the small number on the IV bag with her current Bifocals (BIF). This is causing her neck to hurt. Which of the following lens designs should be discussed with her?

  
  

  a) Progressive lens

  
  

  b) E/D style occupational lens

  
  

  c) Double-segment bifocal lens

  
  

  d) Franklin bifocals


  c) Double-segment bifocal lens
• Which of the following patients would require a balance lens?

  
  

  a) A patient with a prosthetic eye

  
  

  b) A patient who has had cataract surgery on both eyes without a lens implant

  
  

  c) A patient who is blind in one eye from advanced Glaucoma

  
  

  d) Both A & C

  d) Both A & C
• Which of the following patients might require a Fresnel Press-On Lens?

  
  

  a) A patient who is blind in one eye from Glaucoma

  
  

  b) An aphakic patient who has had surgery on one eye only

  
  

  c) A patient who has very high myopia in both eyes

  
  

  d) Both B & C

  b) An aphakic patient who has had surgery on one eye only
• What are three circumstances in which a paraoptometric would specify a base curve when ordering a lens from an optical lab?

  1) The lens powers are very different for each eye

  2) High-Diopter power corrections

  3) Prescriptions for patients who have a sensitivity to base curve changes
• What are two benefits of antireflective coating?

  Antireflective coatings increase the amount of light entering the eye. They eliminate ghost images and light reflections in the lens.
• Which of the following tint grades would be used for a patient who is extremely light sensitive?

  
  

  a) #1

  
  

  b) #2

  
  

  c) #3

  
  

  d) None of the above

  c) #3
• Which tint is commonly known as "blue blocker"?

  
  

  a) Pink

  
  

  b) Brown

  
  

  c) Yellow

  
  

  d) Gray

  b) Brown
• Which of the following would cause a photochromatic lens to darken?

  
  

  a) UV Light

  
  

  b) Warm Temperature

  
  

  c) Infrared (IR) Light

  
  

  d) Both A & C

  a) UV Light
• True or False: "Photochromatic lenses are only available in glass."

  False
• What type of glass is used in the manufacture of ophthalmic lenses?

  
  

  a) Flint

  
  

  b) Crown

  
  

  c) Window pane

  
  

  d) Barium

  b) Barium
• Standard ophthalmic plastic lenses are made from a material called:

  
  

  a) CR-29

  
  

  b) CR-39

  
  

  c) CR-49

  
  

  d) CR-59

  b) CR-39
• Plastic lenses transmit _______________ light _______________ glass.

  
  

  a) The same amount of; as

  
  

  b) Twice the amount of; as

  
  

  c) Slightly more; than

  
  

  d) Slightly less; than

  c) Slightly more; than
• The index of refraction for a polycarbonate lens is:

  
  

  a) 1

  
  

  b) 1.33

  
  

  c) 1.52

  
  

  d) 1.586

  d) 1.586
• Polycarbonate materials filters out _____________ of ultraviolet rays.

  
  

  a) 100

  
  

  b) 99

  
  

  c) 97

  
  

  d) 95

  b) 99
• Which lens material can produce the thinnest, most distortion-free lenses?

  
  

  a) High-index plastic

  
  

  b) Polycarbonate

  
  

  c) CR-29

  
  

  d) CR-39

  a) High-index plastic
• When attempting to dispense the thinnest lens possible, which of the following will reduce the bulge and magnification of plus lenses?

  
  

  a) Larger frame size

  
  

  b) Lower index lens material

  
  

  c) Aspheric design

  
  

  d) Center thickness

  c) Aspheric design
• During chemical tempering of glass lenses for impact resistance, the lenses are left in a hot chemical bath for ________________ hours.

  
  

  a) 11-13

  
  

  b) 13-15

  
  

  c) 15-17

  
  

  d) 17-19

  c) 15-17
• What is compromised when the surface of a glass lens is scratched?

  
  

  a) Lens power

  
  

  b) Index of refraction

  
  

  c) Light transmission

  
  

  d) Impact resistance

  d) Impact resistance
• What is the minimum thickness allowed in the average industrial safety lens?

  
  

  a) 3.0mm

  
  

  b) 2.0mm

  
  

  c) 1.5mm

  
  

  d) 1.0mm

  a) 3.0mm
• A ________________ lens is used to correct a combination of myopia or hyperopia with astigmatism.

  
  

  a) Plano

  
  

  b) Planocylindrical

  
  

  c) Spherocylindrical

  
  

  d) Spherical

  c) Spherocylindrical
• The hard design progressive addition multifocal lenses are recommended for ______________ patients.

  
  

  a) Myopic

  
  

  b) Hyperopic

  
  

  c) Amblyopic

  
  

  d) Emmetropic

  b) Hyperopic
• The Abbé value of Trivex™ is:

  
  

  a) 39-42

  
  

  b) 40-42

  
  

  c) 33-35

  
  

  d) 43-45

  d) 43-45
• For a Progressive addition lens to work properly, the minimum fitting height should ________________________________.

  
  

  a) Be measured at 24mm, for all Progressive types

  
  

  b) Be known before taking the measurement, as each manufacturer may have different fitting heights

  
  

  c) Always match the patient's pupil height

  
  

  d) None of the above

  b) Be known before taking the measurement, as each manufacturer may have different fitting heights.
• What is another name that full-width bifocal lenses may be called?

  
  

  a) Straight-top

  
  

  b) Executive-Franklin

  
  

  c) Round

  
  

  d) Progressive

  b) Executive-Franklin