Progressive Adition Lens

Pal lens Types and design.

1. Kewal Sahu (Optician) MGMEI Progressive Addition Lens

2. Definition – The power of addition gradually increases as the line of the vision sweeps downward through the lens. 2 09.12.2016 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. 3 09.12.2016 History

4. Basic Design in Bifocals 4 09.12.2016

5. Basic design in Trifocals 5 09.12.2016

6. Basic design in PAL 6 09.12.2016

7. Glasses Resins - CR- 39 - Polycarbonate - Trivex 7 Lens Materials 09.12.2016

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 09.12.2016 6 2.0

9. 6 2.0 Distance Reference Circle Fitting Cross Add Power Near Reference Circle Micro-etching Prism Reference Circle Nasal Temporal RE Lens Logo Material Micro-etching 9 09.12.2016 PAL s 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 10 09.12.2016 PAL s 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) 11 09.12.2016 Optical Design

12. Design in PAL’S : Hard design Soft design Advanced soft design Symmetrical design Asymmetrical design Mono design Multi design 12 09.12.2016

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 13 09.12.2016 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 14 09.12.2016 PALs Design Categories

15. Hard and Soft Lens Design Hard Soft 15 09.12.2016

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 16 09.12.2016 PALs Design Categories

17. Contour-plots Give Insufficient Product Information Do you see much difference between these 3 designs ? They look alike… But they perform differently 17 09.12.2016

18. Pattern of PAL’s Symmetrical PAL Identical right & left lenses Lens rotation of two eyes is equal & same amount ( i.e. 10 º ) Nasal decent ration of near zone Imbalance can cause more difficult wearer adaptation 18 09.12.2016

19. Pattern of PAL’s Asymmetrical PAL Incorporated a nasal offset of near zone Negates the lens rotation Leading to better adaptation & visual comfort 19 09.12.2016

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 09.12.2016 20

21. Dispensing PAL….. 21 09.12.2016

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 22 09.12.2016

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 . 23 09.12.2016

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 24 09.12.2016

25. Effect of Vertex Distance Shorter vertex distances increase the field of view through the viewing zones of the lens. 25 09.12.2016

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 26 09.12.2016

27. Effect of Face-Form Wrap Face-form wrap increases the field of view through the distance zone of the lens. 27 09.12.2016

28. PD measurements Monocular PD is more important. Measures from the center of nose to the center of the pupil . 28 09.12.2016

29. PD measurements Methods include Pupillometer Direct pupillary reflex marking method . PD ruler 29 09.12.2016

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 30 09.12.2016

31. Frame Verification Verify frame level with lay-out card followed PD markings. Make sure that frame is suitable for PAL, before fitting. 31 09.12.2016

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. 32 09.12.2016

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 33 09.12.2016

34. No visible segments 34 09.12.2016 Bifocal lens Progressive lens

35. Progressive lens provides clear vision from far to near 35 09.12.2016

36. Extreme right picture shows clear intermediate vision through progressive lens 36 09.12.2016

37. Using the distance vision portion of a bifocal Using the near vision segment of a bifocal Using the intermediate portion of a progressive 37 09.12.2016

38. Perception of form and movement through a progressive lens 38 09.12.2016

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 39 09.12.2016 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 40 09.12.2016 Bifocal vs. PAL s

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