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Ophthalmic Optics > 11 - Progressive Lenses (Exam 3) > Flashcards

11 - Progressive Lenses (Exam 3) Flashcards

1
Q

Can add power of progressive lenses be measured by a lens clock?

A

No

Aspheric curvature gradually changes from distance to near

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2
Q

What is the function of an astigmatic contour plot?

A

Shows distribution and amount of cylinder

Outlines functional areas of the lens

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3
Q

What is the formula for calculating spherical equivalent?

A

Sphere + 1/2 cylinder

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4
Q

What does each line of an astigmatic contour plot usually represent?

A

0.50 D increment of power

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5
Q

What does each line of a mean power plot usually represent?

A

0.50 D increment of power

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6
Q

What does an eye-path power profile graph the relationship of?

A

Power from the fitting cross through the channel and into the near zone

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7
Q

In an eye-path power profile, what % of add power reveals the true corridor length?

A

95%

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8
Q

What are 4 design parameters of progressive lenses?

A
  1. Add power
  2. Corridor length
  3. Near zone width
  4. Distance zone characteristics
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9
Q

Does the “ultimate” progressive exist?

A

NO

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10
Q

What does a wide, clear distance zone in a progressive lens produce?

A

Hard design
Hard line of cylinder along the horizontal axis
Lots of astigmatism below horizontal axis

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11
Q

What does a wide intermediate channel in a progressive lens produce?

A

Soft design
Cylinder introduced into distance zone
Very long corridor

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12
Q

What does a wide near zone in a progressive lens produce?

A

Excessive amounts of blur

“Swimming” sensation

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13
Q

At what distance are wearers of progressive lenses most sensitive to blur?

A

Distance (rather than near or intermediate)

Especially with moving objects

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14
Q

As add power increases, what happens to the near zone?

A

It decreases in size

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15
Q

What is a basic explanation of rotational PALs?

A

Lens used for both eyes

Twisted so near zone was inset for each eye

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16
Q

What is a basic explanation of multi-design PALs?

A

Near zone inset greater with higher add power
‘One design fits all’
Assumes patient’s visual needs are based solely on add power

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17
Q

What is a basic explanation of mono-design (family) PALs?

A

Designs are consistent
Patient only needs to adapt to change in add if they get new lenses and stay in the same design
Require more thought from the practitioner

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18
Q

How do progressive lenses maximize the distance field of view?

A

Congruent distance viewing zones

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19
Q

Where should unwanted cylinder be repositioned in a hyperopic Rx?

A

Distance portion of lens

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20
Q

Where should unwanted cylinder be repositioned in a myopic Rx?

A

Near portion of lens

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21
Q

What types of patients are the most difficult to be successful with in progressive lenses?

A

Emmetropes

Not used to having compromised vision at any distance

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22
Q

What type of lenses can be used to make digitally surfaced PALs?

A

Semi-finished single vision lenses

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23
Q

What are 4 goals of digital lenses?

A
  1. Maximized visual acuity at all distances
  2. Wider intermediate and near zones
  3. Minimal ‘swim’
  4. Wider field of view
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24
Q

What is a large advantage of digital progressive lenses for laboratories?

A

Reduced cost
Due to reduced need for inventory of semi-finished PALs
Semi-finished single vision lenses (much cheaper) can be used

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25
Q

What is the range of fitting heights today for digital lenses?

A

Greater than 11 mm

26
Q

What type of optical materials are available for freeform lenses?

A

Everything except for glass

27
Q

What are the general power ranges of freeform lenses?

A

+6.00D to -10.00D sphere
Up to 4.00D cylinder
Not strict limits

28
Q

What is a general range of costs for freeform lenses?

A

$225 to $800

29
Q

What is the ‘best lens’ on the market today?

A

Freeform (digital) lenses

30
Q

What must you do when selecting a frame for PALs?

A

Pre-adjust the frame

31
Q

What type of PD measurement should you use for PALs?

A

Monocular

32
Q

What 3 things result in PALs as add power increases?

A
  1. Unwanted cylinder increases
  2. Near zone width decreases
  3. Intermediate zone width decreases
33
Q

What types of patients require more time to acclimate to PALs?

A

Patients with high add power

Patients with high distance correction

34
Q

What type of design option is unique to Shamir?

A

Fixed vs. variable corridors

35
Q

How should you choose a fixed corridor length?

A

Closest number to seg height

36
Q

How would a Fixed 11 lens compar to a Fixed 18 lens

A

Fixed 11 has almost no intermediate compared to Fixed 18

37
Q

What type of fixed lens would be ideal for converting a bifocal wearer to PALs?

A

Fixed 11

38
Q

What type of fixed lens would be ideal for converting a trifocal wearer to PALs?

A

Fixed 13

39
Q

When should variable corridor designs be used?

A

Very deep frames (seg height >18mm)

40
Q

Do variable corridor designs give good zone transition?

A

No

41
Q

Comparing soft design to hard design PALs, which are easier to acclimate to?

A

Soft design

because of less unwanted cylinder

42
Q

What is the purpose of prism thinning in PALs?

A

Reduce lens thickness in the near zone to improve cosmetics

Occurs in most PALs

43
Q

Where is the only location in progressive lenses that prism power can be accurately measured?

A

Prism Reference Point (PRP)

44
Q

What is the tool used for identifying PALs and where is it available?

A

Progressive Lens Identifier

The Vision Council

45
Q

What is the Progressive Lens Identifier useful for?

A

Finding the fitting cross location of a given lens design

All are slightly different

46
Q

What is the variance in fitting cross location in different styles of PALs?

A

On the datum line to 6 mm above the datum line

47
Q

What is the datum line?

A

B measurement divided by 2

48
Q

Currently, how many markings are there on digital PALs?

A

Between 8 and 12

49
Q

Where is the add power engraved on PALs?

A

Temporal side

50
Q

Where is the manufacturer’s logo engraved on PALs?

A

Nasal side

51
Q

What type of engraving denotes a short design PAL?

A

An asterisk

52
Q

What are 2 things essential to correcting fitting all PALs?

A
  1. Monocular distance PD measurement

2. Pre-adjust the frame

53
Q

What is 1 essential part of pre-adjusting the frame?

A

Nosepads

54
Q

How many PAL design choices are available today?

A

Over 2000

55
Q

Who is the top PAL manufacturer in the USA?

A

Essilor/Shamir

56
Q

What type of PALs are used for work from 16” to 6’?

A

Computer lenses

57
Q

What are 3 considerations to make with frames for PALs?

A
  1. Deeper is better
  2. Avoid aviator styles
  3. Nose pads are always desireable
58
Q

Where should the fitting cross be located when adjusting a frame with PALs to a patient?

A

Pupil center

59
Q

What must you do with a patient having trouble with PALs?

A

Remark the lenses

60
Q

What are the 3 magical adjustments for a trouble progressive lens patient?

A
  1. Increase pantoscopic angle
  2. Increase faceform
  3. Reduce vertex distance

Ophthalmic Optics (10 decks)

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