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 PRCTICAL DIFFICULTIES OF
PROGRESSIVE LENS FITTING
BRANDS AND DESIGN
 Progressive lenses are by far one of the
most complex lenses on the market. This
often leaves the patient begging to know
what the difference is between brands
and designs.
Adapting To Progressive
Lenses
 The strength of the lens prescription can make
a difference to the ease of adaptation to
progressive lenses.
 When the lens prescription is fairly weak, it is
usually easier to adapt to progressive lenses
than when the lens prescription is strong.
 A strong lens prescription is required for people
whose fields of view are narrow, and these
people should be prepared to take some time
adapting to their new progressive lenses.
Characteristics Of
Progressive Lenses
 To see objects clearly whether they are far away, at a
medium
 distance or close up.
 This is done by blending varying lens powers so that
the eye glass wearer can look through the glasses at
different angles, depending on the type of vision
required.
 The distance section is at the top of the progressive
lenses, and the close-up section for actions such as
reading is at the bottom. The intermediate vision area,
usually suited to tasks about an arm’s length away
such as computer work, is in the centre.
Advantages Of
Progressive Lenses
 Progressive lenses have no visible dividing lines to
indicate that the lens prescription has taken different
levels of vision into consideration.
 The glasses appear to have clear, unlined lenses but
they are actually constructed with a number of curves
through which the progression from one area of focus
to the next is achieved.
 The progression is gradual, meaning that the
progressive lenses enable the person wearing the
glasses to adjust focus smoothly from one area of
vision to the next. The absence of visible dividing lines
on the surface of the lenses also makes progressive
lenses more aesthetically appealing to many eyeglass
wearers.
 Another advantage of progressive lenses
is the variety of choice they offer to people
who need to wear glasses. Depending on
different and individual requirements,
progressive lenses can be customized to
take those requirements into
consideration. Progressive lenses can, for
example, be customized to suit a person
whose day includes a predominance of
computer work and needs glasses with
lenses that make it as easy as possible to
carry out this work.
 When some people begin wearing progressive lenses
in their glasses they may experience some temporary
side effects such as dizziness and headaches.
 These symptoms are often particularly noticeable in
people who tend to suffer from motion sickness. They
indicate that the brain is working to adapt to the
progressive lenses, and usually disappear in the first
couple of weeks. People getting used to new
progressive lenses may also find their perceptions of
depth and distance are altered to some extent initially,
but this usually improves during the adjustment time.
Disadvantages
 Distortion: Progressive lenses suffer the disadvantage
that the power progression creates regions of
aberration away from the optic axis,
 Yielding poor visual resolution (blur). As the lenses
combine a range of powers in a single surface there
are also geometric distortions to the visual field, which
increase with the addition power while the prescribed
addition powers are low.
 The wearer can then adapt to the increases in a series
of steps in addition power over a number of years as
their presbyopia progresses.
 Higher Order Aberrations consists of a
variety of aberrations that have
increasing levels;
 Coma
 Trefoil
 Spherical aberration
 Lower Order Aberrations consist of
sphere and cylinder powers
 Myopia
 Hyperopia
 Astigmatism
 The fitting of individual progressive lens
needs the measurement of individual
data of the face and frames in situ.
Pupillary distance and hight
of the gaze
Lens - Face tilt Working or
reading distance
HARD AND SOFT
 Hard lenses have a much higher
concentration of blending in these zones.
This allows for a much clearer distance
and reading but can give the wearer an
intense 'swimming' feeling
 Later lens designers reduced the
harshness of hard lens designs by
creating the soft lens.
 These lenses increase the blending
zones. This spreads them out into the
distance and reading portion of the lens.
 People who tend to be very active in
their lenses can appreciate the reduced
swimming feeling.
Common difficulties
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Double vision
Blurriness
Ghost images
Halos
Starbursts and bright light
A reduction in visual contrast
Poor night vision
Main Reasons and faults
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Frame selection
Face measurements
Poor handling of lab technicians
Quality and material of the lens
Visible field of area
Ocular physiological problems
Customer satisfaction
conclusion
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Precise eye sight measurement
Careful manufacture
Perfect fitting by lab technician
To train the patient with his full
satisfaction
Thickness and Refractive
index
 WISH YOU ALL ON THIS ALL INDIA
OPTOMETRY CONFERENCE DAY.
 S PALANIAPPAN,HONORARY
OPTOMETRIST AT MILITARY
HOSPITAL,
 CHENNAI