On 7/19/06 3:35 PM, in article
NrednaswY4cKLiPZnZ2dnUVZ_qqdnZ2d@giganews.com, "ACP" <noneone@nowhere.nohow>
wrote:

It makes no sense to me at all. Although I am not a health professional, an
IOL lens that gives best acuity at 9 inches smacks of malpractice. Moreover,
if that were really the case, you would need negative, not positive, lenses
to see clearly farther out.

Bill
-- Ferme le Bush

Your problems with mid range vision with the ReSTOR intraocular lens
(IOL) is not exactly unusual. Some of your problem may relate to the
limitations of multifocal IOLs and some of the problems may relate to
pupil size. There are several important facts about multifocal IOLs
that when combined may explain what you are experiencing.

All multifocal IOLs use rings of different focal range (power)
throughout the IOL. Think of a bull's eye target with each ring
optimized to provide focus at a different distance. No matter what the
design or manufacturer, the transition from one power ring to another
will probably cause a slight blur which often represents as a soft
halo around objects or light sources or just poor vision quality. The
fewer transition rings, the lower the probability of halos or poor
vision quality.

There is only so much light energy that enters the eye. A monofocal
IOL takes 100% of that light energy and optimizes it for one focal
distance. A multifocal may optimize 33% of that light energy for near
distance, 33% for mid distance, and 33% for full distance. That means
that no matter what you are looking at, only 1/3rd of the light energy
is optimized to provide clear focus of the object. The other 2/3rds is
less than optimized. This is a gross simplification of multifocal IOL
technology, but you get the idea.

With a significant amount of the light energy not optimized, you have
out of focus images on top of focused images. This often presents as a
reduction in contrast sensitivity, blur, and/or halos.

The ReSTOR IOL is "apodized". That means that a large central ring of
the IOL is all one focus, rather than a larger number of rings being
of similar and smaller size throughout the IOL. The purpose of the
apodized IOL is to reduce the probability of halos by reducing the
number of transition rings.

One of the limitations of this apodized technique is that the majority
of the light energy is optimized for near vision and for distance
vision. The middle distance vision tends to be of poor focus because a
smaller percentage of the IOL is optimized for mid-distance. For most
people this would mean that a can of beans on the store shelf is a bit
out of focus until you pick it up and hold it close.

It would appear - and this is only an educated guess - that your
correction has put the weak spot of a ReSTOR IOL at the precise
distance you need for computer work...but that is not the end of the
story.

Because the IOL works with rings of different power, the optimized
focus is very pupil size dependent.  Let's go back to that simplified
1/3rd example.

Let us assume that the center of the multifocal IOL is optimized for
near vision, a mid-periphery ring is optimized for mid vision, and the
outer ring is optimized for distance vision. In a bright lit
environment that causes the pupil size to become very small, only near
vision optimized light energy would reach the retina to be seen. If
the pupil were small enough, the rings that provide distance focus and
mid focus would not be used at all because the light that would pass
through that portion of the IOL would be blocked by the iris (colored
portion inside the eye). Again, this is a gross simplification of
multifocal IOL technology, and again you get the idea.

The ReSTOR does have rings with different optimized powers. They are
pupil size dependant. If I recall correctly, the very center of the
ReSTOR is optimized for near vision. When you stick your nose up to
the monitor your entire field of vision is flooded with light emitting
from the monitor. That will cause your pupils to constrict and provide
vision optimized primarily for near vision. This may explain why 9
inches from the monitor you have clear vision. Your pupils are small
AND your IOL is optimized for very near distance with small pupils.

Sit back your desired 36" and try to adjust the light environment at
your computer. Adjust the monitor's bright and contrast down. Adjust
the ambient light down. With a lower light environment your pupils
will enlarge somewhat. After 20-30 minutes, your vision quality may
improve - or may get worse. If vision seems to get worse, turn up the
ambient light and keep the screen dim. See how it is after another
20-30 minutes. If that does not do it, turn up everything and blast
the light at you. Within a few minutes your pupils will constrict, but
I expect that will provide only very near vision of good quality.

By adjusting the light of the computer monitor and the environment,
you can adjust the size of your pupils and thereby hopefully change
the amount of light energy being optimized through your multifocal IOL
for the distance that you need.

You absolutely want to discuss your difficulties with your surgeon and
you must be patient. It takes the brain some time to figure out how to
use multifocal IOLs to the greatest advantage.

If you think that the manufacturers must be crazy to create a
multifocal IOL, do not underestimate the power of the brain to ignore
problems and take advantage where it can. You have a total blind spot
in your field of vision and yet you never see it. Your brain has
learned how to "look around" that blind spot. Similarly, the brain
will learn how to filter out the poorly focused light energy use the
well focused light energy. At least, that is the theory.

Glenn Hagele
Executive Director
USAEyes.org
Patient Advocacy Surgeon Certification

"Consider and Choose With Confidence"

Email to glenn dot hagele at usaeyes dot org

http://www.USAEyes.org
http://www.ComplicatedEyes.org

I am not a doctor.