eric10dpt

respectively). Made several attempts with rgps but couldn't get really good
comfort. There is a tendency to allergic conjunctivitis which is now adressed
by the use of mast cell stabilizers. I haven't tried the influence of mast cell
stabilizers on rgps yet.

Within 4 days I tried both Purevision and Night&Day. Both types of lenses give
me 20/20 vision on both eyes. Also the wetting of the lenses is really good.
Purevision is more comfortable but I could adjust to night&day as well. So, at
the moment I am in favor of Purevision. I have read many times on this group
that night&day does not really last for a whole month. What were your
experiences with Purevision? Does Purevision last longer than night&day?

I need a -9 on the levft eye and a -8.5 on the right. So I need the strongest
power available in Purevision. Night&day goes up to -10. I think it is a shame
that silicone hydrogels are not available in higher powers. I know people who
have 15 diopters of myopia and have to wear conventional lenses.

dr. leukoma

Eric,

I have worn both, but wore the Purevision the most. In the beginning, I
thought that the Purevision was more comfortable. But, after changing to
the steeper base curve in the Focus N&D, I am doing fine with it. Both
lenses have performed well for about their rated life of one month, even on
a daily wear basis (I never sleep in them). I also feel that the oxygen
permeability is more than adequate in either the Purevision or the N&D.

Right now as I look out of my office window at the leaves on the trees and
the blades of grass, I am struck at how clear and detailed everything looks.
I am quite gratified that I can see so well, and so comfortably with contact
lenses. On most days, I am not aware of them. In my mind, the
silicone-hydrogel lenses have been a true technological breakthrough in
contact lenses, and I look forward to more advances and a greater selection
in the future. I predict that within five years, I will not be fitting much
of anything else.

DrG

strongest

shame

who

lothar of the hill people

On Fri, 31 Oct 2003 22:46:15 GMT, "Dr. Leukoma"
<greggem@ix.netcom.com> uttered like so:


I frequently wonder how many doctors actually feel that silicone
hydrogels are safe enough that they would sleep in them themselves.
If you don't mind me asking, do these lenses not work well for you in
overnight wear, or are you just not comfortable with the idea of
wearing them that way? I suppose you've probably seen so many nasty
eye problems in your practice that you are less inclined to risk it
than most patients are!

I've been trying to decide if I should try wearing mine on an
extended-wear basis, and have been wondering how well they hold up to
daily cleaning.

Lothar

dr. leukoma

Lothar, I actually have slept in them by accident, with no untoward effects.
I think that I am just cautious by nature, and that eye doctors in-general
are somewhat conservative. To further underscore the point, I recall
attending a meeting in Houston a year or two ago, and listened to a
presentation by a very well-known academic/research ophthalmologist whose
research has been quite seminal in the understanding of the mechanism of
contact lens-induced corneal ulcers as well as the behavior of the cornea in
the presence of contact lenses. I had been following his research for years
with great interest because of the work he was doing with high Dk lenses,
particularly the silicone-hydrogels. At the end of what amounted to a
rehash and recap of five years worth of data demonstrating the obvious
safety of these lenses, he asked the audience of optometrists the following
question: "How many of you are going to go ahead and prescribe
silicone-hydrogel lenses for your patients on a continuous wear basis as a
result of evidence-based medicine?" The response was only a minority in the
affirmative.

DrG

lothar of the hill people

On Fri, 31 Oct 2003 23:11:39 GMT, "Dr. Leukoma"
<greggem@ix.netcom.com> uttered like so:

I know that concept all too well. As a biologist, I refuse to expose
myself to certain foods and environmental conditions that are
*probably* relatively harmless and that most people wouldn't think
twice about, but my knowledge of potential hazards/complications makes
me wary of them. I'm constantly driving my friends nuts explaining to
them why I'm not willing to try something or another, even as they are
in the middle of trying it themselves. Sometimes ignorance is bliss,
though I prefer to think that knowledge is bliss.

I wonder how many of those doctors actually ended up prescribing them
for extended wear anyway, in spite of their hesitance to raise their
hands in a group of their peers! I'll bet that most of them though
are simply of the old school that says that extended wear is risky,
period, no matter what the lens material, and they're going to be very
slow coming around. I've seen that first hand with my last
ophthalmologist, who refused to let me try Focus Night & Day in spite
of my insistence, but I'd be willing to bet that he will be
prescribing silicone hydrogels within a couple of years.

Lothar

dr. leukoma

If you want something scientific, or pseudo-scientific, I can also add the
following. In general, low water, non-ionic lenses are better for dry eyes.
This favors polymacon 38% water. Next in line would be the FDA Group III
lenses, low water, ionic. Representative lenses are the silicon-hydrogels.
Next comes Group IV, and then Group II, high water non-ionic. I put
Proclears in the latter class, although it would seem to have more of a dual
nature. Some patients seem to follow this trend, while others do not.
Proclears clearly are an improvement in some patients. If these findings
are correct, Focus N&D, which has the lower water content of the Group III
lenses, should perform better.

Incidentally, when I measured water content of a large number of different
lenses, both silicone-hydrogels showed a significant deviation from their
rated percentage of water, 49% vs. 36% for Purevision, and 32% vs. 24% for
Focus N&D. None of the other lenses I measured exhibited a significant
difference between their stated and measured water content.

DrG


strongest

shame

who

lothar of the hill people

On Sat, 01 Nov 2003 15:52:25 GMT, "Dr. Leukoma"
<greggem@ix.netcom.com> uttered like so:


I know that Purevision is a group III lens, but Focus Night & Days are
classified as Group I, if I am not mistaken. Apparently not all
silicone hydrogels are in the same FDA group?

Lothar

dr. leukoma

That's true. There was no classification for the N&D at the time I did my
study, and it seemed to fit the experimental data when lumped with the
Purevision at the time. The most important variable is water content. The
next important variable is how tightly the water is bound, which in the case
of the high water Proclear Compatible the surface water is tightly bound.
However, if one still wants to make a distinction between the two
silicone-hydrogels, the data still seems to favor the Focus N&D, i.e. lower
water, and arguably lower ionicity (maybe).

DrG