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Progressive Additional Lens

Presented by Patidar Rajnandini D.

Chauhan Jinal N.From,BMCO.

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PRESENTATION LAYOUTInformationHistory of PALConstructionMarkingPAL optical designPAL designAdvantages and Disadvantageslimitation of PALMeasurement of PALRe-marking of PALDispensing PALInternal PALPatient maneagementavailability

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INTRODUCTION

What are the Progressive Additional lenses?A lens designed for Presbyopes with Power Gradually increasing from the distance zone through a progreession to the near zone.

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HISTORY of PAL

The concept of PAL has been around since 1907,when first patent on Progressive Power lens was published by Owen Ave.

Varilux 1 was introduced by Essilor in France in the year 1959.

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• 1950 varilux from Essel (Essilor) hard design, symmetric lens• 1970 Varilux II Hard design, asymmetric• 1980 families of lenses (hard soft and in between) Lenses for different patient type or uses• 1990 new soft lenses (multi design) Lenses for all uses and adapted to all prescription. As worn lens design.

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PROGRESSIVE ADDITION LENSES

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PROGRESSIVE LENS CONSTRUCTIONA PAL has a certain distinct areas to the lens but those areas in a progressive lenses are

not visible.

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• Progressive lens will have three distinct zones of vision.

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• DISTANCEThe upper portion of the lens basically for the distance portion .• NEARA designated zone in the lower portion of the lens,which

provides the necessary near addition or near power.• INTERMEDIATEA corridor in the central portion of the lens connects these two

zones, which increases progressively in plus power from the distance to near.

This zone is also known as “ Progressive zone ”.

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PROGRESSIVE ADDITION LENS MARKING

• All progressive addition lenses contain important markings , which are used to identify lenses and to assist in their fitting and verification.

• The impotant markings are explained below.

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Progressive Marking

1. Itching points :(in fig A.)

2.Distance optical centre(DOC):

(in fig B.)

• They are two hidden circles, which are permanent mark on the lens at 34mm apart .

- When the ink marking is removed , they are made visible by fogging.

• Also known as prism reference point.

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3.Add power :(in fig C.)

4.Axis line :(in fig D.)

5.Distance power circle :(in fig F.)

• Hidden addition power situated at the temoral side and is made visible by fogging.

• 0-180 degree axis line passing through the DOC.

• This is the distance power circle to check the exact distance power with the help of lensometer.

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6. Fitting cross :(in fig E.)

7. Hidden logo :(in fig G.)

8. Near vision circle :(in fig H.)

• Fitting cross lies above the DOC.

• Situated nasally and is made visible by fogging when the ink mark is removed.

• 7mm to 9mm circle is the centre of the near vision area and is inset by 2.5mm.

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PAL OPTICAL DESIGN

1.Add power .2.Lengt of Progressive Corridor.3.width of distance and near zone.

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CONT…..1.Add Power:• The amount of astigmatism will be directly proportional

to the add power of the lens.

• E.g. A +2.00D addition will generally produce twice as much cylinder error as +1.00D addition.

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2.Length of the Progressive Corridor:• Shorter corridors produce more rapid power

change and higher levels of astigmatisms , but reduce the eye movement required to reach the near zone.

• Larger corridors provide more subtle power changes and lower levels of astigmatism , but increase the eye movement required to reach the near zones of the lens.

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• How the length of the Progressive Corridor and the add power can affect the rate of change and magnitude of the astigmatic error?

• *consider :- Addition= +2.50D corridor height=17mm so, 2.50/17=0.15D per millimeter

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• Therefore, the power of Progressive lens change has more rapidly down the Progressive corridor, as the addition power increases or the length of the corridor decreases.

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3.Width of distance and near zone:• Wider distance and near zones confine the

astigmatism to smaller regions of the lens surface which produces higher levels of astigmatism.

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PAL DESIGNS

• Mono design and Multi design• Asymmetry and symmetry design• Hard and soft design

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Mono design

• All Progressive had a single design for all power, is called mono design.

• In case of mono design PAL, a single design is used for all addition powers.

• E.g. mono design Ready stock progressive lenses.

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Multi design

• In multi design the position for near vision changes with the addition power change.

• In starts from soft design for low add power, as the add power increases it will turn to hard design lenses.

• Multi design tends characterstics change with priscription.

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Symmetric design

• In case of symmetrical progressive addition lens design,the right and left lenses are identical.

• Add is straight down from distance optical centre.

• Required rotation to achieve desired inset for near.

• E.g: 10 degree clockwise in left lens,and anti-clockwise in right lens.

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Conti…..

ADVANTAGES• We can give the inset

accordings to patient.

• No difference between right and left blank.

DISADVANTAGES• Disruption of binocular

vision as the wearer gazes laterally across the lens, since the astigmatism differed between the nasal and the temporal side of the distance zone.

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Asymmetric design

• Lens have preset inset for near.• Different lenses for right and left.• There is no need of the lens rotation in this

case.

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Cont…….

Advantages• Better adaptation.

• Improve binocular vision.

• More visual comfort and better convergence.

Disadvantages• Fixed inset may not match

with patient`s required inset.

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Hard design

• Hard design is basic design, regular distance single vision.

• Wider distance zone.• Wider near zone.• More narrow and shorter progressive corridor.• More rapidly increasing levels of astigmatic

error.

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Cont……

Advantages• Large distance and near

area free from astigmatism.• Wider near zone even at

high RX.• Require less eye movement.

Disadvantages• High intensity aberration at

periphery .• More adaptation time .• Swim effect.

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Soft design

• Very useful for intermediate zone.• The soft design is one in which the change

from the near zone to the peripheral area is gradual when compared with a hard design.

• A soft design has a slower vertical change in power as the wearer looks from distance to near.

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Cont…..

• Narrow distance zones.• Narrow near zone.• Longer and wider progressive corridor.• More slowly increasing level of astigmatic

error.

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Cont……

Advantages • Soft design are easier ,More

rapid adaptation times

• Reduce swim effect.

Disadvantages• Smaller field at sharp vision.

• Need dropping of eye farther near to read.

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PAL. ADVANTAGES AND DISADVANTAGES

Advantages

1. No visible line .2. Looks like a single vision.3. More natural vision, Continuous field of vision.4. More visual comfort.5. No image jump in vision from distance to near areas .6. Comfortable intermediate vision.

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dis

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Limitations of PAL Lens1. Differing Magnification throughout the lens:

• The changing curves on the front lens surface and the change in power throught of the channel and reading portion of the lens create varying magnification through out the lens.

• The result is that the vertical lines viewed through the progression zone exhibit skew distortion.

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Cont……

2. Restricted visual field:• Progressive addition lenses restrict our field of

vision particularly for intermediate or near areas.

3. Compromised Optics:

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Cont……

4. No control over the Inset of the Near Portion:

• Some progressive addition lens designs do have an inset , which varies with addition and/or distance correction, but not yet with interpupillary distance.

5.Difficult to check with Focimeters:• Progressive addition lenses are relatively difficult to

check with the help of focimeter.

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Measurement of progressive lenses

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RE-MARKING PAL

1ST STEP: Find hidden circle located 0-180 degree line, 4mm below the fitting cross of the lens.

2nd STEP: Below these hidden circle the near addition power on the temporal side and symbol identifying the particular lens on

the nasal side.

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3rd STEP: Place the lens on the respective brand layout card with two circles of the lens coinciding with the two circles on the card.

4th STEP: now mark the other markings.•The following option may be followed , --the micro ictching can be detected by reflecting light from the overhead lights of the lens surface.--Fogging the lens surface breathing warm moist air on the lens surface.--Position the light source behind the lens.

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Layout of progressive addition lens

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Essilor ZeissSeiko

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FRAME FRONT ADJUSTMENT

PANTOSCOPIC TILT

FACIAL WRAP

TEMPLE LENGTH

VERTEX DISTANCE

MONOCULAR PD

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DISPENSING PAL1. Frame Front Adjustment: • Adjust the angle of the temples so that the

frame sits squarely on the face.

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CONT……..

2. Pantoscopic tilt:

• Adjust temples to achieve 8 to 12 degrees tilt, avoid contact with cheeks.

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CONT….

3. Facial Wrap:

• Ensure that the front of the frame follows the line of the face but not excessively.

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CONT…

4.Temple length:

• Adjust length of temple to minimize sliding .

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CONT…..

5.Vertex Distance :

• Minimum vertex distance by adjusting by adjusting nose pads but avoid contacting the eyelashes with lens.

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CONT….6 .monocular PD :

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CONT……

7.Fitting Height:

The fitting cross on progressive addition lens must coincide with the pupil centre of the wearers in their natural posture.

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Internal PAL• It is a big step forward in overcoming many of the

limitations of progressive lenses .• Seiko is first internal Progressive lens.• In an internal progressive lens,the curves producing

changing power are positioned on the back surface of the lens,and front surface is spherical.

• The design provides a field of vision that is 30% wider than a front side progressive lens because of progressive surface rests closer to the eyes.

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Cont......

1. Expansion of the visual fields.

2. Magnification differences between various areas of the lens are reduced.

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Tools for comparing Progressive Lenses1.Cylinder Contour Plots

( Isocyl charts)

Define the shape and width of the various zones.

show areas of equal cylindrical power on the front surface.

Or areas of equal cylindrical power in a given range.

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CONT.......

•Hard and Soft design contour plots

.

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CONT......

Usefulness of Contour plots:They can give useful information about the design type .

bThey can allow some comparisons with other designs.

Problems with contour plots: They only describes the shape of the front surface.They can not predict actual performance accurately

They do not consider other aberrations.

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CONT…..Problems with contour plots:

They only describes the shape of the front surface.

They can not predict actual performance accurately.

They do not consider other aberrations.

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CONT........2. Spherical Contour Plots;

•Define the length of the progression.• Show areas of equal spherical.

Power on the front surface.

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CONT…..

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CONT.........3. Isoacuity Plots:

•Define the useful zones of lens.

•Show areas of equal visual acuity.

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CONT……

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Determining Patient Suitability

1. OccupationRelative need for: Distance/ intermediate/near.

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CONT…….. Direction of gaze requirements:

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CONT…

3.ContraindicationsField of view:

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CONT………

•M

obility/head m

ovement:

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CONT……

Prescription :

1.Anisometropia2. Antimetropia3.High Cyls for certain axes

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Relative need for

Distance/ intermediate/near

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Direction of gaze requirements

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Fitting and Dispensing Progressive Lenses.

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• Fitting and Dispensing Progressive Lenses

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Delivery

1.Pre-delivery VerificationChecking the markings.Checking the frame details.Checking the distance Power and Prism.

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2.Remedies for Manufacturing Errors

1. Heights 2. Monocular PDs 3.Lenses swapped 4.Wrong power 5.Axis error

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3.On Eye Assessment

1.Check frame fit2.Check the position of the fitting crosses3.Check distance vision4.Check near vision5.Remove the ink markings

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•Checking the fitting cross heights and monocular PDs

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Patient Management

•How to use the lenses .•Troubleshooting

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Availablity• Digital • Seiko• xperio• Shamir• Hoya • Sola• Kodak• Zeiss• younger• Essilor (varilux physio DRx) varilux is the top brand for PAL ,now. the top progressive lens brand due to

the technology and research used in manufacturing a lens that will create a sharp image and smooth transition from different distances.