[Leica] Advice with Progressive Lenses

[Richard Clompus <rclompus@voicenet.com>]

Carol asked about progressive lenses and photography.  

As in camera optics, much as changed with the optics used in spectacle
lenses.  When you reach age 40 or more, the eyes have lost some of their
ability to focus close.  Its as if we are all born with built in "macro
lenses" that become more like "non-macro lenses"  after age 40.   

Bifocals (lens with distance and near optics) have been available since
Benjamin Franklin.  He actually invented them.  The problem is our
lifestyle and visual requirements have continued to change.  We need help
in focusing at distance, intermediate (arms length) and at near for
reading.  A trifocal lens can be used for this but is often heavier and you
now have three segements to deal with.

A progressive lens is more like a zoom lens that focusses smoothly from
distance to near by lifting your chin so that you view through lower areas
of the lens.  The optics have improved considerably in the past five years.
 In optics there is no free lunch.  The lens designer has to provide a wide
enough channel to view at the intermediate and near distances.  Aberrations
are pushed peripherally - that include induced astigmatism.  Fortunately,
the eight pound mass that sits on our shoulders (brain) has a trmendous
ability to process visual information.  Almost a third of it is dedicated
for this purpose.  The brain uses the information and tends to suppress the
distortion.  After a week, many patients don't notice any peripheral
distortion.  

Each lens company believes they havemade the best choices and compromises
in their progressive design.  Zeiss makes a Gradal progressive lens from
Germany.  Varilux makes a Comfort progressive lens from France.  It was
actually the French who came up with this design concept in the 1960's.
Most modern progressives work very well.  Coupled with a UV 400 blocker and
a five layer super anti-reflecive coating, they are marvels of optical design.

Some people can't adjust to progressives or even bifocals.  I am
sympathetic to them.  Using these lenses is a great convenience.  Most
people do well when prescribed and fitted well.  When measuring a patient
for progressive lenses, you have a tolerance of only 0.5mm to line them up
in the frame.

Finally, the size of the frame is often linked to fashion trends.  Kind of
reminds me of how men's ties go wide and then narrow and then wide again.
In optics, smaller is almost always better.  The larger you go, the thicker
the lens becomes and the more peripheral distortion you create.  Smaller is
thinnner, lighter and fewer distortions.  You must have a minimal size for
the optics to fit but Europe leads th way over Amercia for optical design.
Smaller is in for the moment. 

Talk to your doctor and make sure if you don't adapt for any reason, they
offer to remake your lenses into a visible bifocal at no additional charge.  

Happy shooting,

Richard
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Richard Clompus, OD
West Chester, PA, USA