Progressive addition lens1

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.

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

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

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

Hoya GP Wide Hoya GP Wide Panamic Rodenstock Life 2 Zeiss Gradal Top Sola Max Zeiss gradal top Comparison

Progressive addition lens1

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