Re: Progressive Lens Choices

On Sun, 10 Feb 2008 11:10:32 -0800 (PST), DAB <David.Boulifard@xxxxxxx> wrote:

It's probably safe to ignore the VI (vertical imbalance) with this type of Rx.
However, if you wear multifocals, and you experience fatigue after a long
stretch of close work, VI might be the culprit.

Could VI be one of those things taken into account by the computer
programs that calculate "individualized" lens surfaces?

Hopefully soon.

In other words, better quality lenses do not make up for bad opticianry.

If I lived within an hour of Wauwatosa, I'd beat a path to your shop.
I do know of a "Guild" optician in my area. Does that designation
count for something extra these days?

It shouldn't rule anyone in or out. It doesn't sound like you'll have any
problems finding out who's competent.

Depends on the material choice, service, and the type of aberrations and
distortion that needs to be minimized. However, looking at your situation; ie,
changing from SV to a +2.00 Add PAL (progressive addition lens), I'd probably
give the nod to the Hoya lens due to how well it reduces skew distortion,
amongst other factors. The less expensive iD Lifestyle would be very close in
performance, and comes in Trivex. Both come in two corridor lengths- the longer
one (14mm) will have the best distance vision, and will still be ok for close
tasks.

I checked out Hoya's web-posted information on the iD Lifestyle, and
it looks like an excellent choice on multiple criteria: design,
materials, coatings. (It seems, however, that the longer corrider
version is 18mm vs. the 14mm you cited.)

Hoya is describing the minimum fitting height- the lens with an 18mm minimum
height has a 14mm corridor, the 14mm minimum height has a 11mm corridor.
Regardless, you'll probably do better with the former.

I also received a reasonable
price quote from the aforementioned Guild optician, which would put a
second pair of the same lenses adjusted for office use well within
range (pun not intended).

You might not need the very best lens for the computer glasses- the reduced
minus and Add power might make a less expensive lens design more than adequate.
However, if the frequency of use is high, the increase in visual refinement
with a more advanced design would probably be worth the expense, pocketbook
willing.

I was impressed by Hoya's (realistic?) illustration of reduced swim
effect on stairs. I'm surprised they don't tout it as a safety
issue. But I wonder if anything in particular is attributable to the
front-back split of the reading correction. Couldn't a ray-tracing
program compute a back-only surface with identical performance?

I'm told that what can be done on two surfaces can also be done on one surface,
at least in regards to power and astigmatic error, and maybe unwanted surface
astigmatism. However, Hoya is not just splitting the Add power on both surfaces,
they're combining two plano cylinders on the front and back surface that sums
the cylinder power to equal the Add power. This is said to reduce skew
distortion, to a degree that can't be done working only one surface.

You still might need an additional pair of single vision for music- use a +1.50
or +1.75 for the Add, or if you need distance capability, then a high set ST35
(a wider than normal lined bifocal). However, you might find the computer
glasses adequate for the *** music. Make sure that the optometrist or optician
shows you the quality of vision at both 20" and 30", using a variety of power
combinations.

I've been thinking about some of the peculiarities of the piano
application. When marking music, it helps to see clearly at 12"
inches. When reading music, it helps to see clearly at 20" for an
upright, 30" for a grand. When positioning fingers on the keyboard,
freedom from spatial distortion matters, so playing without refraction
might be best. When playing in an ensemble, seeing other people's
facial expressions at 6 to 12 feet can be important.

Consider an upside down half-glass reader. I used to get these from the now
defunct Franel Optical. Great for myopes- set the focal length as needed and
look underneath the frame for the real short distances.

Perhaps no single design can meet all these requirements optimally at once?

Usually not, especially for advanced presbyopes.

Hope this helps,
Robert Martellaro

It does. I've leared a lot from your posts, here and on OptiBoard.

That's good to hear. I want consumers to have more knowledge, asking tough
questions, making it easier for you to find competent opticians, especially in
states where opticianry is not regulated.

Robert Martellaro
~~~~~~~~~~~~~~~~~~
Optician/Owner
Roberts Optical
Wauwatosa Wi.
~~~~~~~~~~~~~~~~~~
"Science is a way of trying not to fool yourself."
- Richard Feynman
.