This document provides information about progressive addition lenses (PALs), including their history, design, markings, fitting process, advantages, and disadvantages compared to bifocal lenses. Some key points: - PALs were invented in the late 1950s and gradually increased in popularity as an alternative to bifocal lenses that provides clear vision from distance to near without visible lines. - PAL designs can be "hard", with a rapid progression, or "soft" with a slower progression. Designs also differ in the size and location of distance, near, and intermediate zones. - Fitting PALs properly requires selecting the right frame size and shape, measuring pupillary distance and fitting heights, and ver

2.  Definition –
The power of addition gradually increases as the line of
the vision sweeps downward through the lens.
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Progressive Addition Lens

3.  Benjamin Franklin invented first bifocal
spectacle lens in 1784.
 First patient on progressive power lenses
was published in 1907 by Owen Ave.
 Forerunner of Essilor company introduced first
commercially available PAL Varilux 1, in 1959.
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History

4. Basic Design in Bifocals
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5. Basic design in Trifocals
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6. Basic design in PAL
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7.  Glasses
 Resins
- CR- 39
- Polycarbonate
- Trivex
7
Lens Materials
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8. All PALs contain important markings which are
used to identify lenses & to assist in their
fitting & verification .
- Permanent Marking
- Ordinary Marking
8
PALs Markings
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62.0

9. 62.0
Distance
Reference Circle
Fitting Cross
Add Power
Near
Reference Circle
Micro-etching
Prism
Reference Circle
NasalTemporal
RE Lens
Logo
Material
Micro-etching
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PALs Marking

10.  Distance & near reference points for power measurement
 Fitting cross for fitting purposes
 Prism reference circle for prism measurement between
lenses
 Micro etching for re-marking purposes
 Peripheral lens aberration in peripheral zone
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PALs Marking

11.  Power progression by increasing the front surface
curvature from dist to near zone
 Rate of power progression determines the length of
intermediate zone
 The position of the near zone is offset nasally
(convergence for near)
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Optical Design

12. Design in PAL’S :
 Hard design
 Soft design
 Advanced soft design
 Symmetrical design
 Asymmetrical design
 Mono design
 Multi design
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13. Hard design –
 Rapid progression from dist to near power
 Large dist & near zone ( free of aberration area)
 Shorter & narrower intermediate zone
 More adaptation time
 People who do a lot of reading
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PALs Design Categories

14. Soft design –
 Slower progression from dist to near power
 Smaller dist & near zone ( free of aberration area)
 Longer & wide intermediate zone
 Less adaptation time
 Young presbyopes
 Active outdoor profession
 Professional driver
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PALs Design Categories

15. Hard and Soft Lens Design
Hard Soft
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16. Advanced soft design –
 The progression zone is similar to a hard design
 Larger effective distance and near zones
 Unwanted cylinder(induced astigmatism)is pushed
towards the periphery similar to a soft design.
Therefore giving wider and larger intermediate zone
 Peripheral aberrations are very well controlled, so the
wearer gets adapted very easily
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PALs Design Categories

17. Contour-plots Give Insufficient Product Information
Do you see much difference between these 3 designs ?
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18. Pattern of PAL’s
Symmetrical PAL
 Identical right & left lenses
 Lens rotation of two eyes is equal & same amount ( i.e.
10º )
 Nasal decent ration of near zone
 Imbalance can cause more difficult wearer adaptation
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19. Pattern of PAL’s
Asymmetrical PAL
 Incorporated a nasal offset of near zone
 Negates the lens rotation
 Leading to better adaptation & visual comfort
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20. The other design considerations are …...
 Multi-design Vs Mono-design :
 In Multi-design the position for the near vision
changes with the addition power increase end
the near area goes up with the increase in the
addition which improves the comfort of the
wearer
 In Mono design the position of the near vision
doesn’t change with the addition powers- thus
causing difficulty while viewing near
objects/prints as the wearer holds the reading
material closer to him as his add power increases
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21. Dispensing PAL…..
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22. Fitting Progressive Lenses
When fitting progressive lenses, use the following
procedure:
1. Select the frame
2. Pre-adjust the frame
3. Measure the fitting heights
4. Measure the distance PDs
5. Verify lay-out card
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23. Dispensing PALs – Frame selection
 Metal frame with adjustable pads is a good option.
 Frame height require to ensure adequate area for distance
& near.
- at least 18 mm below and
- at least 14 mm above from the pupillary center.
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24. Pre-Adjust the Frame
 Ensure a minimal vertex
distance
 Ensure at least 7° or
more of Pantoscopic tilt
 Ensure a sufficient
amount of face-form
wrap
 Adjust frames with
demo lenses in place
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25. Effect of Vertex Distance
 Shorter vertex distances increase the field of view
through the viewing zones of the lens.
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26. Effect of Pantoscopic Tilt
Pantoscopic tilt brings the near zone closer to the eye and
increases the field of view through the near zone of the
lens
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27. Effect of Face-Form Wrap
 Face-form wrap increases the field of view through
the distance zone of the lens.
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28. PD measurements
 Monocular PD is more important.
 Measures from the center of nose to the center of the
pupil.
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29. PD measurements
 Methods include
Pupillometer
Direct pupillary reflex marking method.
PD ruler
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30. Verify cut-out card
 Use the correct cut-out
card for the lens design
 Place the dotted demo
lens on the fitting point
of the Lay out card, and
ensure that the frame will
cut- out at the desired
measurements
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31. Frame Verification
 Verify frame level with lay-out card followed PD markings.
 Make sure that frame is suitable for PAL, before fitting.
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32. Key points to success with PALs
 An accurate refraction.
 Correct size of frame and
adjustments
 An accurate monocular PD
measurements.
 Perfect fitting.
 Proper instruction on use.
 Motivate the patient to adapt the
new type of vision.
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33. Advantages of PAL
 No visible segments.
 Continuous field of clear vision
 Comfortable intermediate vision
 Continuous support to eye’s accommodation
 Continuous perception of space
 Lighter & thinner than single vision of the same power
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34. No visible segments
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Bifocal lens Progressive lens

35. Progressive lens provides clear vision from
far to near
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36. Extreme right picture shows clear intermediate vision
through progressive lens
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37. Using the distance vision
portion of a bifocal
Using the near vision segment
of a bifocal
Using the intermediate
portion of a progressive
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38. Perception of form and movement through a
progressive lens
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39.  Straight line appears curved
 Adaptation required
 Peripheral aberration
 More steps in fitting
 Increase in eye and head movement
 Eye must be dropped a longer distance
 Expensive compared to bifocals
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Disadvantages of pal

40. Bifocal
Provide distance &
near vision only
Distinct junctions
between zones
Lower cost
Fast fitting procedure
Prismatic image jump
Cosmetically
unappealing
PALs
Provide intermediate
vision also
No visible junctions
between zones
More cost
More steps in fitting
No prismatic image jump
Cosmetically appealing
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Bifocal vs. PALs

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