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  • Physiological Considerations
  • Usable Field of View
  • Binocular Vision
  • Peripheral (Extra-Foveal) Vision
  • Advantages
  • Advantages
  • The Optics of Progressive Lenses
  • Hard vs Soft Design
  • Asymmetrical Design
  • Differentiate one design from another.

Progressive addition lens1 Progressive addition lens1 Presentation Transcript

  • PROGRESSIVE ADDITION LENS: OPTICS AND DESIGN SHRESTHA GS, M.Optom
  • Presbyopia correction
    • PALs
    • Enhanced near vision
    • Bifocals
    • Trifocals
    • SV (readers):
      • full aperture
      • half-eyes
  • RANGE OF CLEAR VISION Single vision Bifocal Progressive 0.33 0.50 1.00 2.00 5.00 NEAR INTERMEDIATE DISTANCE NEAR INTERMEDIATE DISTANCE NEAR INTERMEDIATE DISTANCE
  • PURPOSE
    • Understand experience with current correction
    • Highlight limitations of current correction
    • Explain feature/benefits
    • Refer to “change in vision” when refitting into different design
    • Listen to the wearer’s needs
    • Restate the wearer’s needs (avoid technical jargon)
    • Make the recommendation
  • What are progressive addition lens ?
  • Physiological Considerations Distance Intermediate Near Typical dioptric power (D) for clear viewing of objects
      • The usable field of view is comprised of head and eye movements as shown here for the horizontal plane.
    Usable Field of View Eye rotation Head movement PALs design and personal movement characteristics
  • Binocular Vision Binocular vision: As the patient’s gaze is lowered for near objects, the eyes converge to maintain a single binocular image. The progressive lenses should ensure that this is maintained for different object distances from the eyes, as illustrated by the lines.
  • Peripheral (Extra-Foveal) Vision Peripheral vision: The PAL design should ensure that *objects in the periphery of the visual field are easily fused. **The distribution of prism in each lens should also be balanced for binocular viewing. ***Corresponding areas in the two lenses should provide a similar level of vision.
  • Why Use PALs?
    • Uninterrupted vision from distance to near
    • No visible line
    • No jump in vision from distance to near
    • Better vision as intermediate is clear
    • Looks like single vision
    • Lighter/thinner than SV
    • Looks better
    • More natural vision
    • More visual comfort
    • Confidence in mobility
    Feature Benefit
  • Intermediate Vision
    • Intermediate vision:
    • (a) Poor head position as a consequence of the eyes searching for the best focus in the bifocal’s limited range of intermediate clear vision. (b) Using the intermediate portion of a PAL enables more natural head position.
    (a) Bifocal (b) PAL
  • Why Use Progressive Lenses? Bifocal lens Progressive lens The bifocal lens (left) can disrupt the patient’s view with visual disturbances (arrows) when the eye crosses the boundary of the near seg. The progressive lens (right) has no such problem and enables a smooth transition between different reading distances.
  • PAL references
  •  
  • How a progressive addition lens works?
    • Invariably follow the traditional lens optics
    • Power in the midline follows the same distance prescription as addition increases below until desired add is reached
    • For the most of the lenses, this addition power is reached at a point 10-16mm below and 2.0-2.5mm nasal from distance optic centre
    Width = Lens design + Add Astigmatic error = Width of near area + add
  • Progressive Lens Design - Optics Distance Zone Near Zone Umbilical line Intermediate Zone Lens Radius Changes Along Umbilical Line
  • Principal parameter :
    • Size of distance & near area
    • Type and intensity of aberration
    • Depth & usable width of corridor
  • Design in PAL’S :
    • Hard design
    • Soft design
    • Symmetrical design
    • Asymmetrical design
    • Mono design
    • Multi design
    • Prescription based design
  • Progressive Lens Design 2. Hard Vs Soft Lens Design Hard Soft
  • Hard design
    • Regular distance single vision
    • Spherical distance zone
    • Wide distance & near zone
    • Narrow & short intermediate corridor
    • Rapid increase in unwanted astigmatism
  • Advantages
    • Large distance & near area free from astigmatism
    • More accessible with downward rotation of eye
    • Wider near zone even at high Rx
    • Disadvantages :
    • High intensity aberration at periphery
    • Distortion for longer and more difficult period of adaptation
    • Swim effect
  • Soft design :
    • Aspheric upper halves
    • Narrower distance & near zone
    • Wide & large intermediate corridor
    • Gradual increase in unwanted astigmatism
  • Width of Far V ision (+4mm): 0.5 [D]- 16.2 mm 1.0 [D]- Unlimited Max Cylinder [D]- Nasal: 1.5[D] Max Cylinder [D]- Temporal: 1.5 [D] Width of Corridor (-6mm): 1.0[D]- 9 mm Length of corridor: 14.2 mm Minimum fitting: 19 mm Width of near Vision (-18 mm): 1.0[D]- 21.63 mm Soft Design
  • Advantages
    • Decreases intensity aberration at periphery
    • Easier, more rapid adaptation
    • Less distortion of peripheral viewing
    • Reduce swim effect
    • Disadvantages :
    • smaller field at sharp vision
    • Need dropping of eye farther near to read
  • Indication for selection
    • Hard design :
    • Previous successful hard lens wearers
    • People who do a lot of reading
    • Soft design :
    • Young presbyopes
    • Active outdoor profession
    • Professional driver
  • Symmetrical design :
    • Add is straight down from distance optical center
    • No right & left lenses
    • Required rotation to achieve desired inset for near (9 degree)
    • Advantages :
    • We can give the inset according to patient
    • Disadvantages :
    • As the wearers looks to the side they will experience different power & differential prism
  • Asymmetrical design :
    • Lenses have pre-set inset for near
    • Different lenses for right & left
  • Progressive Lens Design 3. Symmetrical Vs Asymmetrical Symmetrical PAL - same lens design is rotated to fit the other eye Asymmetrical PAL - each eye has a different lens
    • Advantages :
    • This will not produces experience of different power when patient looks to a side
    • Disadvantages :
    • Fixed inset may not match with patient’s required inset
  • Mono design :
    • Describe range of power for a given design
    • It classify hard & soft
    • It describe the characteristics of progressive zone
    • Maintain design principles throughout the range of addition
  • Multi design :
    • According to add power lens design changes
    • It start from soft design for low add power & as the add power increase it will turn to hard design lens
    1.50 Add Design 2.00 Add Design 2.50 Add Design
  • Prescription base design :
    • Result of years of Vision Research
    • Dedicated design for every Base and Add
    • Design by Base : different designs for Hyperopes, Emmetropes and Myopes (FOV & Magn.)
    • Design by Add: effective near zone sizes change as the add increases
    • Near inset position varies relative to level of Presbyopia / reading distance
    • Corridor length also varies relative to both Base and Add
  • Incorporating Single vision aspheric design in to the PALs
    • Aspheric advantage
    • Flat, thin, lighter
    • Earlier front surface aspheric design
    • Back surface Aspheric design
    • Bi-aspheric design
  • USE OF CONTOUR PLOT TO EVALUATE PROGRESSIVE LENSES
    • Distortion of grid patterns viewed through the lenses
    • Visual acuity attainable at different portions
    • The amount of vertical imbalance at paired peripheral points
    Areas of equal cylinder power plotted with a connecting line- Isocylinder line Equal spherical equivalent powers-
  •  
  • Lens Design Selection
    • Consider how the wearer uses their lenses
      • for most wearers a good modern progressive lens design is the best solution
      • but not all designs provide wide fields of view at distance, intermediate and near
      • consider the design that will suit the wearer
        • general purpose : balanced fields of view
        • mainly for reading : wide near visual fields
        • mainly for computer : wide intermediate visual fields
          • Contour Plot Description
          • Design Technology
          • Visual Boundaries
          • Performance Implications
          • Growing Product Category
    Knowledge continues to Evolve Summary
  • Disadvantage of PALs
    • Straight line appears curved
        • More adaptation
    • Decreased width at intermediate and near
        • Limited lateral movement
    • Increase in eye and head movement
        • Eye must be dropped a longer distance
  • Rodenstock Perfect read R
    • For half eye reading glass users who need trifocal
    • Ordinary PALs to much peripheral aberration occurs
    • Use of full lens useful area
    • Near power is the reference power
    • Near IPD is the measured estimation
    • Power of the lens starts out with intermediate prescription
  • Varilux readable
    • Full working field enjoy as single vision lens for intermediate and near
    • Much clearer intermediate which can’t be attained by single vision lens
    INTERMEDIATE +0.75 +0.75 12mm 4mm 28 mm
  • Cosmolit P
    • Aspheric thin design
    -0.75D Add 20mm 10mm
  • Overview
    • Electricians, plumber, painter, pharmacists, librarians
    41mm Add-0.50 9mm
  • Technica
    • Soft design of 1.00cyl max
    Distance Intermediate Near MRP: 50% 0f add
  • Some of the common Progressive lens from essilor
    • Espace: affordable price and field of vision for all distances
    • Adaptor; soft design, good distance, optimized intermediate and wide near vision area
    • Varilux comfort: sharp and natural comfortable vision, good distance, optimized intermediate and adequate near vision area
    • Varilux comfort 1.6: Thinner and lighter than normal progressive
    • Varilux panamic: wide field of vision for all distances
    • Varilux panamic 1.6:
    • Nicon Presio: wider intermediate and near zones, for small size frames
    • Comfort transition: progressive +photochromic
    • Nikon web.lens: enhanced near vision for computer savvy presbyopes
  • Sola Progressive
    • Solamax: highest reading area, Spectralite; thinnest of all
    • Percepta: wider clear vison for all
    • XL gold: intermediate for sports and arm length activity
    • Graduate: first time wearer, wide distance and near
    XL Graduate
  • Computer lens 12 mm power transition zone Access uses a unique aspheric surface: Upper portion for mid-range distances Lower portion has reading Rx Power varies smoothly from top to bottom Mid-range Near
  • ACCESS TM
    • Breaks the Mid-Range Barrier
    • Access provides
      • Extended range
      • Wider breadth of field
      • Mid-range vision is as wide as close-up vision
      • Continuous vision throughout the lens
      • Ease of use
  • mc compared to Adult Progressive Lenses Addition Power Plot mc Myopia Control Standard Adult Progressive Short Corridor Adult Progressive
  • Eye tracking
  • R1 Far Zone Rn Progressive Zone R2 Near Zone Controlling the distortion is the key to the ultimate progressive lens Topographic Map Minimizing Distortions
  • The technology that enables us to design progressive lenses through an exact simulation of the natural human eye view. Eye Point Technology
  • The optical power is created by 3 parameters: thickness, index and curvatures The surface of the lens is scanned by a 3D measuring system, mapping the curvatures of the lens. Eye Point Technology
    • The surface data & a highly advanced mathematical algorithm are the basis to Shamir's Eye-Point Technology™, which takes into account numerous parameters:
    • Lens index refraction
    • Lens prescription
    • Lens center thickness
    • Distance from the eye to the back vertex of the lens
    • Distance from the lens to the object
    • Object's angular position in the eye's field of vision
    • Pantoscopic tilt of the frame
    • Pupil distance
    • Thickness reduction prism, and more.
    • By taking all of these parameters into consideration, Shamir's Eye-Point Technology™ enabled the creation of the perfect progressive lens.
    Eye Point Technology
  • Visual Simulator
  • Panamic Panamic Rodenstock Life 2 Hoya GP Wide Zeiss Gradal Top Sola Max Analyzed by Rotlex Class I on a random lens Panorama Gold Comparison
  • Rodenstaik life II Sola Max Sola Max Panamic Rodenstock Life 2 Hoya GP Wide Zeiss Gradal Top Comparison
  • Comparison
  • Hoya GP Wide Hoya GP Wide Panamic Rodenstock Life 2 Zeiss Gradal Top Sola Max Zeiss gradal top Comparison
  • Thank you