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OPT 2461L Ophthalmic Dispensing Lab 2 > UNIT 2: Progressive Addition Lenses > Flashcards

UNIT 2: Progressive Addition Lenses Flashcards

1
Q

Why did PAL’s take so long?

A
  • Simple to conceive but challenging to produce
  • Machinery capable of creating non- regular
    surfaces had to be created.
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2
Q

Creating Progressive Power

A
  • Increased curvature creates more plus power (
    with a stable index)
  • Aspheric curvatures needed to create plus
    power on PAL’s
  • Increasing power creates surface astigmatism
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3
Q

How is surface astigmatism created?

A
  • Due to the changing surface curvature.
  • It is an unwanted by- product of aspheric
    curvature.
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4
Q

What does surface astigmatism do?

A

It blurs vision just as if the wearer were looking through incorrectly prescribed cylinder.

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5
Q

Hard Design PAL’s

A
  • Concentrates the astigmatic error into smaller
    areas of the lens surface.
  • Expands the areas of perfectly clear vision.
  • Higher levels of blur and distortion.
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6
Q

List 4 characteristics hard PAL’s exhibit

A
  • Wider distance zones
  • Wider near zones
  • Shorter, narrower progressive corridors
  • Higher, more rapidly increasing levels of
    astigmatic error
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7
Q

In general, harder PAL designs:

A
  • Provide wider fields of view
  • Require less head and eye movement
  • Provide more swim and blur
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8
Q

In general, softer PAL designs:

A
  • Provide reduced levels of astigmatism and
    swim
  • Limit the size of the zones of clear vision
  • Require more head and eye movement
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9
Q

Softer Design PAL’s

A
  • Spreads astigmatic error across larger areas of
    the lens surface.
  • Reduces the overall magnitude of blur
  • Narrows clear vision zones
  • Astigmatic error may encroach well into the
    distance zone.
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10
Q

List 4 characteristics soft PAL’s exhibit

A
  • Narrower distance zones
  • Narrower near zones
  • Longer, wider progressive corridors
  • Lower, more slowly increasing levels of
    astigmatic error.
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11
Q

When was the concept of PAL’s patented?

A

1907

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12
Q

What was the first progressive lens marketed in the world?

A

Varilux by Essilor

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13
Q

When was Varilux marketed to the world?

A

1956

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14
Q

Who designed Varilux?

A

Bernard Maitenaz

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15
Q

What material is Varilux made in?

A

Glass

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16
Q

What design was used in the upper half of Varilux and why?

A

Spherical design used to create a large, clear distance zone with no surface astigmatism.

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17
Q

FILL IN THE BLANK
All progressive power is centered in a ________ intermediate zone in a Varilux lens.

A

12mm

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18
Q

FILL IN THE BLANK
Power in the lower portion resulted in a ______ wide stable and essentially spherical zone.

A

22mm

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19
Q

What type of design is Varilux considered?

A

Hard design

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20
Q

What was the first US PAL’s?

A

Omnifocal

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21
Q

Who designed Ominfocal?

A

David Volk and Joseph Weinberg

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22
Q

When was Omnifocal designed?

A

1961

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23
Q

TRUE OR FALSE
Omnifocal was sold by Univis Lens Company in 1973.

A

False: 1965

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24
Q

What material is Omnifocal made in?

A

Glass only

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25
Q

In omnifocal lenses, is the decreased radius of curvature vertical or horizontal?

A

Vertical

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26
Q

TRUE OR FALSE
In Omnifocal, it has a narrowing corridor design from top to bottom.

A

True

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27
Q

How much distance is between the distance and near centers of a Omnifocal lens?

A

25mm

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28
Q

What kind of progressive design is Omnifocal lenses?

A

Soft Design

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29
Q

When was Varilux updated to Varilux 2?

A

1972

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30
Q

Varilux 2

A
  • Released in both glass and plastic materials.
  • Lens completely aspheric
  • Soft design
  • Tilted corridor in its design
  • Creates true right and left lens blanks
  • Eyes experience equal power changes as they
    scan around the lenses binocularly.
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31
Q

Who introduce UltraVue?

A

American Optical

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32
Q

When was UltraVue introduced?

A
  • UltraVue 25 in 1975
  • UltraVue 28 in 1979
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33
Q

UltraVue

A
  • Had a large, wide, and clear distance zone free
    from astigmatism.
  • Progressive power within 10-12mm in the
    intermediate zone.
  • Wide essentially spherical near zone.
  • Had high levels of surface astigmatism
    peripherally and closely positioned to the
    corridor.
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34
Q

In UltraVue, was the corridor tilted?

A

The corridor is NOT tilted

35
Q

How was UltraVue made?

A
  • Using one lens blank rotated nasally right or left 10 degrees by the lab to create the appropriate lens.
  • Creating approximately a 2.5mm near zone inset.
36
Q

What does the single blank design of UltraVue present?

A

Unequal powers to the eyes scanning binocularly.

37
Q

Varilux Infinity

A
  • Introduced multi-design
  • 12 Designs: one for each add power
    (+0.75D to +3.50D)
  • Low add = soft design with a long corridor
38
Q

Asymmetrical Design

A
  • Introduced by SOLA Optical (1987) with the
    SOLA XL lens
  • Distributed unequal amounts of surface
    astigmatism on either side of the umbilical
    midline.
  • Placed more surface astigmatism in the lower
    nasal portion than in the temporal and
    peripheral portions.
  • Concept = surface astigmatism in the lower
    nasal portions of the lens is relatively
    unnoticed.
  • Also aided in reducing the overall amount of
    surface astigmatism in the lens.
39
Q

Various Segment Inset

A
  • As the eye tracks down the progressive
    corridor into the near zone, it encounters
    prismatic effect.
  • Pulls the eye off the midline.
  • Adjust the location of the near zone to
    compensate for prismatic effect.
40
Q

In short corridor progressives, what corridor length keeps surface astigmatism low?

A

Long ; some lenses had corridors as long as 25mm

41
Q

In short corridor progressives, what frame size had shallower B measurements?

A

Small ; Longer corridor lenses didn’t fit (The near zone was cutoff in edging)

42
Q

AO Compact

A
  • First short corridor lens
  • By American Optical
  • 15mm min recommended fitting height
  • Ideal for shorter/ smaller/ shallower frame
    styles.
  • Still on the market
  • Nearly every major lens manufacturer offers
    one or more short corridor progressive
    designs.
43
Q

What is optical ray tracing used to determine?

A

How an object will image on the film in a camera.

44
Q

What can ray tracing tell a designer?

A
  • Illustrate areas of blue, distortion and
    magnification.
  • Illustrate the amount and the axis of surface
    astigmatism at various points of the lens.
  • Illustrate lens aberrations and distortion, mag
    and other optical focusing characteristics.
45
Q

Where does vision occur?

A

In the visual cortex of the brain.

46
Q

Who was TruVision Technica designed by?

A
  • American Optical ( 1988 )
47
Q

TruVision Technica was designed to provide what?

A
  • Width of lens intermediate and near viewing
  • Small, usable distance window for viewing
    objects across the room or on the wall.
48
Q

When was Hoyalux TACT introduced?

A

1998

49
Q

What does Hoyalux TACT offer?

A
  • Wide intermediate and near zones with limited
    distance vision.
  • 2 fitting heights:
    1) EP40 - Standard viewing position
    - Wide near vision, limited elsewhere
    - 40% of the add power at the fitting cross
    location.
    2) EP60 - Near vision position
    - No distance area but a good
    intermediate and very wide near zone.
    - 60% of the add power at the fitting cross.
50
Q

Near Environment Lenses

A
  • Computer lenses
  • No distance zone
  • Progressive power more gradual
  • Less aberrations, distortion, and blur.
  • Not meant to replace progressives
51
Q

What is Rodenstock Impression ILT?

A
  • One of the first individualized progressives
  • 2001
  • Aspheric / atoric back surface for this front surface PAL’s
52
Q

Varilux Ipseo

A
  • Individualized progressive
  • Takes into account the patients visual behavior
    to create a progressive that’s individualized.
  • Uses The Vision Print System
53
Q

Vision Print System

A
  • Measures head and eye movement of patient
  • Translates into visual behaviors fingerprint
  • Data used for customization of lenses
54
Q

Two ways to create direct to surface application?

A

1) Making molds
2) Cutting the surface directly on the lens blank

55
Q

Mold Making

A
  • Traditional progressives are cast
  • Monomer takes the shape of the two molds
56
Q

What are traditional progressive molds made of?

A

Slumping

57
Q

Slumping

A
  • The glass mold material is heated and takes
    the shape of the die use.
  • Two molding processes are used:
    1) One making the mold
    2) Another when making the lens
58
Q

Direct to Surface Mold Making

A
  • Mold is created by direct surfacing
  • Accuracy is improved: approximately 0.01D
    ( conventional molding accurate to 0.06D )
59
Q

Direct to Surface Lenses

A
  • Created when one surface is directly surfaced
    to direct to surface generation.
  • Direct-to-surface PAL’s are produced several
    ways.
    - Generate the lens distance power on the
    backside.
    ( for a front surface progressive design )
  • Direct-to-surface cuts the progressive surface
    onto the lens.
  • Both sides surfaced using direct to surface
    processing.
60
Q

Vertical Alignment

A
  • Sit across from the patient so that you are
    at the same eye level.
61
Q

TRUE OR FALSE
Sighting upwards ( sitting too low ) gives lower segment height measurements.

A

TRUE

62
Q

TRUE OR FALSE
Sighting downward ( sitting too high ) gives lower readings.

A

FALSE: Gives higher readings

63
Q

Horizontal Alignment

A
  • Be sure that the midline of your face is
    aligned with the midline of the patient’s
    face.
  • If you are positioned to the right or left, the
    markings placed on the lenses will be
    incorrectly positioned by equal amounts to
    the right or left.
64
Q

Fitting Height Measurement

A
  • Seated in proper facial alignment, have the
    patient gaze into your left eye.
  • Measure from the inside of the frame’s
    bezel ( frame groove ) to the center of the
    patient’s pupil.
  • For frames with demo lenses, you can
    simply mark the lenses at this location.
  • Without moving your head, have the
    patient look into your right eye and take
    the second measurement.
  • Again, without moving your head, repeat
    both measurements to ensure accuracy.
65
Q

What are traditional fitting measurements limited by?

A
  • Accuracy
  • Precision
  • Reliability
  • Consistency
66
Q

What factor is accuracy affected by and what is it?

A

Parallax Error: The apparent displacement of the wearer’s pupil at the plane of the spectacle lens as the dispenser changes position.

67
Q

What is precision limited by?

A

The measurement tool

68
Q

What does the pupilometer measure?

A

Corneal reflex

69
Q

Corneal Reflex

A
  • Reflex is independent of the dilative state
  • Reflex is easy to locate/measure
  • Eye’s optical axis falls close to the reflex
70
Q

Fitting Height

A

The distance between the center pupil & the lowest edge of the lens.

71
Q

Optimal Lens Tilt

A
  • Lens tilt influences the optics
  • Most PAL’s are designed for about 8
    degrees vertical tilt.
  • Wrap brings the periphery of the lens
    closer.
72
Q

Modern Measurements

A
  • Customized PAL’s may require additional
    measurements.
    • As Worn:
      • Tilt, Wrap, Vertex
      • Head Cape, ERCd
    • Personal Visual Habits:
      • Head/ Eye Movement
73
Q

FILL IN THE BLANK
_____________ progressive lens base curves are calculated on averages, and if a patient’s distinct requirements fall beyond this range, vision is ________________.

A

1) Traditional
2) Compromised

74
Q

Computerized Measurement Systems

A
  • Pupil Meter & Pupilometer Pro for Ipad
  • Optikam
  • Zeiss: iTerminal
  • Essilor: Visioffice
  • Hoya: Spectangle
75
Q

The Centration Module

A
  • Anatomically adjusted frame
  • Patient stands or sits in relaxed, habitual
    posture.
  • Unique, patented speckle image causes
    patients eyes to relax for accurate distance
    PD measurement.
  • A precision digital camera captures front
    and side images of the patient in his or her
    chosen frame.
  • Sophisticated software makes all key
    measurements to an accuracy of 0.1mm.
76
Q

Lens centration and fitting

A
  • i.Terminal incorporates unique, patented
    laser speckle target system.
  • Ensures that the wearer maintains proper
    distance fixation while the photo is
    captured, and that the wearer is properly
    centered in front of the system.
  • Automatically compensates for any
    accidental head rotation.
77
Q

Lens centration and fitting

A
  • i.Terminal incorporates unique, patented
    laser speckle target system.
  • Ensures that the wearer maintains proper
    distance fixation while the photo is
    captured, and that the wearer is properly
    centered in front of the system.
  • Automatically compensates for any
    accidental head rotation.
78
Q

Carl Zeiss Vision

A
  • Zeiss Individual
  • Additional customization if iTerminal is
    used.
  • Measures:
    • Monocular P.D.
    • Fitting Height
    • Vertex Distance
    • Frame Wrap
    • Pantoscopic Tilt
79
Q

The Consultation Module

A
  • High resolution photo images allow patient
    to see clearly how they will look in their
    chosen frames.
  • Images can then be enhanced to show the
    appearance and effects of:
    • AR Coating
    • Photochromic
    • Fashion Tints
80
Q

Eye Rotation Center

A
  • Point through which optical axis always
    passes.
  • Determines optical projection on the retina.
81
Q

What is Head Cape?

A
  • The measurement of the natural resting
    position of the head.
  • Each 2 degree of head cape results in 1 mm
    horizontal shift.
  • Studies show the average head cape is
    approximately 1.5 degree.
82
Q

Progressive Lens Markings

A
  • Distance verification circle
  • Near verification circle
  • Fitting cross
  • Prism reference point ( PRP )
  • Datum line ( 180 degree line )
83
Q

How is fitting height verified?

A
  • Using a mm ruler
  • Lens cut out chart

OPT 2461L Ophthalmic Dispensing Lab 2 (4 decks)

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