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Lensa progresif
1. PROGRESSIVE LENS
Refraction, Contact Lens and Low Vision Sub Division
Department of Ophthalmology
Medical Faculty of Andalas University/ DR. M. Djamil Hospital
Padang
2019
MEIRONI WAIMIR
Literatur Review
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2. INTRODUCTION
Progressive Addition Lens /PAL
A corrective lens used in eyeglasses to correct
presbyopia and other disorders of accommodation
ďą Characterized by a gradient of increasing the lens power
ď added to the glasses.
ďą Power gradually increasing from the distance zone, through a
progressive zone to the near zone.
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3. INTRODUCTION
1907
first
patented by
Owen Aves
1922
Duke Elder
developed the
world's first
commercially
PAL
1953
Bernard
Maitenaz,
patented Varilux
and introduced
in 1959 by
Essilor
1972
Maitenaz created a
truly aspherical
design and
manufacturing
process (Varilux 2)
1983
Carl Zeiss AG
developed free-form
technology and has
been patented
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4. ď§ Progressive lens ď a type of multifocal lens that has a
surface with a continuous smooth increase in addition (plus)
power.
ď§ Gradual increase in power ď intermediate zone
DESIGN AND CHARACTERISTICS OF
PROGRESSIVE LENS
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5. Gradual increase in
curvature
DESIGN AND CHARACTERISTICS OF
PROGRESSIVE LENS
Produces a corridor
that progressively
increasing plus power
Variable focus
intermediate zone
All three zones are enclosed on both sides by blending regions and
geometric distortions
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6. ⢠Bifocal Lens
Has two fixed focus vision zones, separated by visible
discontinuity ď image jump
Intermediate vision is often limited
DESIGN AND CHARACTERISTICS OF
PROGRESSIVE LENS
⢠Progressive Lens
Provide the desired add power without any breaks, ledges or
lines by blending the transition between the distance and near
zones.
The transition ď very smooth enough to prevent sudden
changes in image jump.
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7. EARLY PROGRESSIVE LENS DESIGN
⢠Owen Aves (1907) ď dual surface progressive lens design
section of a cone on one side and elliptic cylinder on the other.
⢠The progressive region of the surface can be represented by
circular cross section that gradually decrease in diameter,
thereby increasing in curvature ď Elephantâs trunk.
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9. CHARACTERIZING PROGRESSIVE LENS
⢠In the blending region there is a contour plot that shows the optical
quantity levels of the lens.
⢠Progressive lenses have an astigmat plot like finger print ď useful
for evaluating the strength distribution of additions.
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10. The rate of change in cylinder power away from the progressive
corridor increases as the Add power of the lens increases
CHARACTERIZING PROGRESSIVE LENS
The rate of change in cylinder power away from the progressive
corridor increases as the length of the progressive corridor
decreases
Minkwitzâs Theorem
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11. DISTRIBUTION OF SURFACE OPTICS
Wide distance and reading zones
Narrow intermediate zones
Close spacing of contour lines
Reduced distance and reading zones
Wider intermediate zone
Wide spacing of contour lines
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12. ADVANTAGES OF PROGRESSIVE LENS
⢠Progressive lenses provide the correction that presbyopia
patients need to see clearly at all viewing distances.
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13. ADVANTAGES OF PROGRESSIVE LENS
⢠Comfortable intermediate vision
Using the distance vision
portion of a bifocal
Using the intermediate
portion of aprogressive
Using the near vision
segment of a bifocal
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14. ADVANTAGES OF PROGRESSIVE LENS
⢠Progressive lens avoid discontinuities (image jumps) that are
found with bifocal and trifocal lenses.
⢠More cosmetically attractive ď no line of damarcation
In PAL, an uninterrupted curves links distance vision, intermediate
vision, and near vision with no visible separation
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16. The Best Candidates for PAL are :
⢠Patients with early presbyopia who have not previously worn
bifocal lenses.
⢠Patients who do not require wide near-vision fields.
⢠Highly motivated patients.
Patients who change from conventional multifocal lenses to PAL
should be advised that distortion will be present and adaptation will
be necessary.
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17. PROGRESSIVE LENS FITTING
⢠Lens manufacturers now offer PAL ď more compact, smaller,
more fashionable frames and still get the full effect from the
lens.
⢠The main difference between lenses is the width of the central
corridor.
⢠Wider intermediate area ď the patient who works on the
computer.
⢠Wider reading area ď the patient who spends a significant
amount of time reading.
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18. PROGRESSIVE LENS FITTING
Additional information that will assist in selecting progressive lens
that will provide the best possible vision, including:
ď§ Patientâs prescription
ď§ Patient's occupation
ď§ Leisure time activities
All information collected will help in choosing the right design.
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19. Step 1. Frame Selection
PROGRESSIVE LENS FITTING
⢠Frames accomodate the lenses, fit comfortably, suit the patientâs face
shape, and be stylist.
⢠Check the frame before taking any measurements.
⢠Vertex distance (12-14 mm), face form, and pantoscopic tilt 8-12
degrees.
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20. PROGRESSIVE LENS FITTING
Step 2. Frame Measurements
⢠Place properly adjusted frame on patient
⢠Mark each lens at the pupil center with a
felt-tip marker.
⢠Draw a horizontal line on each lens
⢠Check to see that the lines are at the center
of each pupil.
⢠Measure fitting height from the deepest
point of the lenses to the pupil center.
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21. ⢠Take monocular PD measurements.
⢠Use a corneal reflex pupillometer to ensure exact measurement
of center pupil.
⢠Take PD measurement for infinity and near and record the
measurement
PROGRESSIVE LENS FITTING
Step 3. Pupillary Distance (PD) Measurement
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22. ⢠Use the card provided by the progressive manufacture to check
lenses.
⢠Use the patientâs fitting height and distance PD measurements.
⢠Place lens cross over the layout chart to verify the lens will fit in
the frame.
⢠If it does not fit, select another frame.
PROGRESSIVE LENS FITTING
Step 4. Check Lens Cut Out
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23. Patient Education - Adaptation
PROGRESSIVE LENS FITTING
⢠Always wear progressive glasses during activities.
⢠To see an object on the side, turn your head, don't glance
because it will cause visual distortion.
⢠Do not look at the edges of the lens because these are
distortion areas on the progressive lens.
⢠If you cannot adapt yet, it is not recommended to ride
using progressive glasses.
⢠Move the eyes when looking at objects or text above and
below.
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24. CONCLUSION
Progressive lenses are eyeglass lenses that ideal for presbyopia
because providing a continuous increase in the plus power focus
to compensate lack of accommodation. The progressive lens
allows clear vision for distance, intermediate and near zone
where dioptric power gradually increases along the lens surface
from the top to the bottom.
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25. Progressive lens provides comfortable intermediate vision,
avoid image jumps, and more cosmetically attractive. The
disadvantages of progressive lens are there is peripheral
distortion, requires fitting, and more expensive than other
multifocal lenses.
Progressive lens fittings is important to get the best vision and
patient comfort in using progressive lens glasses.
CONCLUSION
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Characterized by a gradient of increasing the lens power which is added to the correction of the glasses.
Additional power ââdepend on the patient's presbyopia level. In general, the older the patient, the higher the addition.
PAL was first patented by Owen Aves in 1907 This patent includes a manufacturing process and design that is not commercialized.
Duke Elder in 1922 developed the world's first commercially available PAL. Carl Zeiss AG & Varilux lenses are the first PAL with a modern design.
Bernard Maitenaz, patented Varilux in 1953 and the product was introduced in 1959 by SociĂŠtĂŠ des Lunetiers (Essilor). However, the surface structure of the first Varilux lens is still close to a bifocal lens, with half the upper surface which is free of aberration for distant vision and the segment is rather large for near vision.
1972 with the introduction of Varilux 2, which Maitenaz created a truly aspherical design and manufacturing process.
Carl Zeiss AG developed free-form technology in 1983 and has been patented
The curvature of the lens surface increases from the minimum value in the distance zone to the maximum value in the near zone.
Gradual increase in power also results in a variable focus intermediate zone
This discontinuity gives a sudden change in the size and location of the image, known as the image jump
Owen Aves (1907) His invention was ď dual surface progressive lens design section of a cone on one side and elliptic cylinder on the other.
The cone provides a progressive increase in curvature through the horizontal line of the lens, while the elliptic cylinder provides a progressive increase in curvature through vertical meridians roughly equal to horizontal curvature at the corresponding points on the opposite surface.
In general, progressive lens consist of 4 structures
1. Distance zone: a stable region in the upper portion of the lens that provides distance prescription.
2. Near zone: a stable region in the lower portion of the lens that provides add power for reading.
3. Progressive corridor: a corridor of increasing power connects these two zones and provide intermediate or mid range vision.
4. Blending region: peripheral region of the lens contain non prescribed cylinder power and provide only minimal visual ability.
Surface astigmatism varies across the surface a progressive lens ď zero along progressive corridor ď increases into lateral blending regions ď unwanted cylinder power ď blur, distortion, and image swim
This contour plot also shows the potential for blur, image swim, and image distortion which are useful for predicting the size of the distance, intermediate and near zones.
Picture : Contour plots show the distortion of an optical quantity- such as unwanted astigmatism (cylinder power) or mean add power indicating its level in fixed intervals (ex. 0.50 diopters)
Picture: the surface astigmatism of a progressive lens is proportional to Add power, and unwanted cylinder power of a +3.00. Add lens is roughly equal to three times the cylinder power of a +1.00 Add lens
Progressive lenses are often classified as hard and soft design based on distribution of surface optics
Harder design
Progressive lens design concentrate the astigmatism into smaller regions of the lens surface, so it expanding areas of clear vision by raising unwanted cylinder power inthe periphery. It consequently offer wider distance and near viewing zones, but higher levels of blur and distortion in the periphery.
2. Softer design
Progressive lens design concentrate the astigmatism into larger regions of the lens surface, so it reducing unwanted cylinder power in the periphery. It consequently offer less blur and distortion in the periphery, but narrower viewing zones.
Picture: Progression of power in relation to viewing distance, head posture, and eye movement
Using the distance vison of a bifocal.
Using the near vision of a bifocal.
Using the intermediate portion of a PAL
Lens power increase smoothly from the distance vision area at the top of the lens, through an intermediate vision area in the middle, to the near vision area at the bottom of the lens.
Peripheral Distortion: Progressive lenses have aberrations region and geometric distortions in the periphery, leading to poor vision when turning the eyes down and to the sides.
Fitting: Progressive lenses require careful placement of the wearer's pupil centre for a distance-viewing reference position. Incorrect specification of the fitting location can cause problems for the wearer including narrow fields of view, clear vision in one eye only, on-axis blur, and the need to alter the natural head position in order to see clearly.
Cost: Progressive lenses are more expensive than bifocal and single-vision lenses due to higher manufacturing and fitting costs.
Progressive lenses have become the most popular style of lenses for those who need near correction, but donât want the age-revealing lines in their glasses.
patient prescription: affect lens design and material.
Patient's occupation: how patients use their eyes at work will determine progressive design.
Leisure time activities: do they use significant near vision. This information will help in choosing the right design.
All information collected will help determine whether the patient needs a wider reading area or shorter intermediary area
Because it has three functions (distance, intermediate,and near), progressive glasses are not immediately comfortable when worn. New users must experience a period of adaptation in using progressive lenses