I  am currently wearing Focus Night&Day in the Left Eye, and Purevision
Toric in the Right Eye. I am myopic and presbyopic (56 years old), the right
eye is fitted for distance, the left for near work.

I sleep with the lenses on, however usually take them out to clean them once
a week, and leave them off overnight before reinserting. About once per
month I change to new lenses.

Both lenses are comfortable, but I find the N&D a little more comfortable
than the PV. (Or, that may have to do with toric vs. non-toric.) Sometimes
the right eye gets a little red.

So, I was looking at the Cibavision site, and it looks like they now have a
silicon hydrogel toric lens. Surprisingly, it is not called Night&Day Toric,
but AirOptix for Astigmatism.

Is that the same material as N&D? As breathable as N&D? How do they compare
to Purevision Toric?

I haven't read up on contact lenses for awhile. Is there anything new in the
way of soft multifocals? I tried the Purevision Multifocals once, they did
not work so well, so I went back to monovision. Are there any other silicon
hydrogel multifocals out now? I see that Ciba now has what appears to be a
multifocal toric, called "Progressive Toric". Is that a silicon hydrogel? (I
am surprised that all soft lenses are not si-hy by now, due to the much
better breathability.)

What else is new in the world of silicon hydrogels? Is there anything out
now, that beats N&D as far as breathability, and perhaps comfort?

Thank you for your input.

(I hope there are still some knowledgeable eye docs and laymen reading this
forum, where helpful people used to willingly share their knowledge.. I see
so much spam here, it is hard to find the real posts. It is sad, what has
happened to Usenet, overtaken by spam, trolls, etc.)

Interesting that since the first si-hy lens came out, N&D, several years ago
now, no other lens has overtaken, or even matched it, in dk/t. (Correct me
if I'm wrong about that.) I know you wrote that as far as comfort is
concerned, higher dk/t is not necessarily more comfortable. But how about
for eye health? Wouldn't the more oxygen permeability=better for the eyes?
I'm surprised that the manufacturers (including Ciba) have not tried to
create lenses with higher dk/t than N&D. (Or perhaps they did try, but so
far have failed?)

Also, since N&D and Purevision came out, several years ago, have there been
no other lenses approved for 30 day wear? I'm surprised at that as well.
Since you write that AirOptix has higher dk/t than Purevision, and PV has
been approved for 30 day wear, wouldn't it make sense for AO also to be a 30
day lens? Or, do the lens manufacturers just now want to deal with the
testing process any more, that they have to go through, to get lenses
approved for 30 day wear?

(As mentioned, although wearing N&D and Purevision, I usually take out my
lenses once per week, clean them, leave them out overnight. So, I guess 6 or
7 day lenses should be fine for me. But, if I hear a lens has been approved
for 30 day wear, I figure that that lens is probably healthier to sleep in
at all, than a lens approved for 7 days. So, I'm surprised if no
manufacturers try to get that 30 day approval any more.)

So--are you saying that the lenses which are supposed to be better for dry
eyes, even with the word "Aqua"  in them, which one would think have a
higher water content, actually have a lower water content--like Oasys, Air
Optix Aqua, etc.? Do those lenses have a lower water content than N&D?

What about Biofinity? I remember positive comments about that lens here,
when it was first coming out, about a year ago. How does that compare to the
others?

So, of the si-hy toric lenses, do the Air Optix for Astigmatism lenses have
the highest dk/t? How do the Oasys torics compare in that regard?

How about multi-focal si-hys? Are the Purevision the only one out there
still? That's surprising to me too. With the increased aging of the baby
boomers, increased presbyopia, a lot of people wanting to look younger, not
wear reading glasses, etc., one would think that there would be a lot of
research and development into multi-focal designs. Is that not happening?

Thanks again for the info, Dr. Leukoma. More questions below....

"Dr. Leukoma" <d... at (no spam) leukoma.com> wrote in message

news:0d0fe68f-805e-4fae-8269-0ad9e09355ab at (no spam) a1g2000hsb.googlegroups.com...

Pure silicone is hydrophobic.  The dk/t of a silicone-hydrogel lens is
inversely related to the water content.  Focus N&D is 24% water.  Air
Optix is 33% water.  Oasys is 38% water, etc.  There is a body of
literature relating to overnight corneal swelling and the dk/t of a
lens.  With respect to this factor, dk/t definitely matters and the
higher the better.  It has been suggested that the minimum dk/t for
safe overnight wear should be 125.  But, the point is that beyond that
number what are the tradeoffs with respect to comfort, wettability,
etc. of increasing the silicone content?

---------------------my response---

In that case, would you consider Focus N&D to be the safest lens to wear
overnight? I'm still surprised then, that manufacturers have not tried to
surpass it, in terms of dk/t. (Or, have they tried to do so, and failed?)
(One could wonder as well, why Cibavision has made a toric version of
AirOptix, without making any toric version of the more permeable N&D?)

One would think that, even if the minimum dk/t considered safe for overnight
wear is 125, that minimum should not be good enough, and that they would try
to make the lenses as safe as possible for overnight wear, while of course
trying to retain comfort, etc. Perhaps N&D went as far as that can go, but I
would think that, with modern science, they could achieve still higher dk/t,
while preserving comfort, etc.

Also, you wrote that the lesser the water content, the better for dry eye..
Yet, Oasys is advertised as being especially good for dry eye, yet it has a
higher
water content than N&D. Is N&D actually better for dry eye than Oasys?

-------------------Dr. Leukoma wrote----------------------

I believe that the reason might be that for safety reasons the lens
manufactures have decided not to go in that direction and also because
most eye docs are conservative and adhere to the minimum amount of
overnight wear for their patients.

-----------------my response--------------------

Yes, I can imagine that even with 30 day lenses, many docs recommended that
their patients take them out and clean them more often. In fact, that's what
my eye doc recommended, and I take them out and clean them (and leave them
out overnight), every 7 days. However, as I mentioned, if I hear a lens has
been approved for 30 day continuous wear, I would tend to think (even if
incorrectly), that that lens is safer for any kind of EW, even one night,
than lenses approved for a smaller time period. I would think it
advantageous for the manufacturers, to get that approval. (Is it true that
some lenses are approved for 30 day wear in Europe, but not in the US? Why?
Does the US gov have much stricter testing requirements than the EU?)

----------------Dr. Leukoma wrote----------------------------------

See my post above.  HOWEVER, remember that thickness also determines
how much oxygen gets to the eye through the lens, and some lenses
might be thicker than others, thereby equalizing the playing field
somewhat.

--------------------my response-----------------------

Yes, but doesn't the letter "t"  in dk/t refer to thinness? The dk is the
inherent permeability of the material, and the t is the thinness of the
lens, which together make up dk/t, the permeability of the lens. So, isn't
thinness already part of the equation, when one looks at dk/t numbers?

Thanks again for your responses, Dr. L.!

The dk/t changes with lens thickness. If there were not differences
in thickness across the surface of the lens, it would have no
refractive power.