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si hy lens experiences
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Dr. Leukoma
medicine forum Guru


Joined: 30 Apr 2005
Posts: 1283

PostPosted: Tue Jul 18, 2006 11:34 am    Post subject: Re: si hy lens experiences Reply with quote

Dr. Leukoma wrote:

Quote:
nobody can convince me that they are by far the better option for most
SCL wearers. This is despite whatever articles you might have read in
the "throwaway" journals.

DrG

Nobody can convince me that they are NOT by far the better option for
most SCL wearers, that is.

Not for 100%, but for most, IMO.

DrG
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Anon E. Muss
medicine forum Guru Wannabe


Joined: 22 May 2006
Posts: 136

PostPosted: Wed Jul 19, 2006 12:04 am    Post subject: Re: si hy lens experiences Reply with quote

On 18 Jul 2006 04:13:49 -0700, "Dr. Leukoma" <drg@leukoma.com> wrote:

Quote:
Anon E. Muss wrote:

[snip]

Both of these problems (Si-Hy CLs depositing easier and stagant
tears/inadequate tear circulation under contact leading to
CLARE/keratitis [not tight lens syndrome]) occuring have been
documented, mentioned and discussed in several journal articles over
the past couple years.

Sorry, but can you cite the article(s)? I am aware that si-hy lenses
are more prone to lipid spoilation.

There are a ton of articles. If you read the journals related to
contact lenses, I don't know how you could miss them.

However, here are some regarding their *depositing* more than HEMA
lenses do:

o Jones L, Senchyna M, Glasier MA, Schickler J, Forbes I, Louie D,
May C. Lysozyme and lipid deposition on silicone hydrogel contact lens
materials. Eye Contact Lens. 2003;29(1 Suppl):S75-S79; discussion
S83-S84, S192-S194.
o Jones L, Senchyna M, Louie D, Schickler J: A comparative
evaluation of lysozyme and lipid deposition on Etafilcon, Balafilcon
and Lotrafilcon contact lens materials. Invest Ophthalmol Vis Sci
2001; 42: s593 #3186.
o Ghormley N, Jones L: Managing lipid deposition on silicone
hydrogel lenses. Contact Lens Spectrum 2006 21;1: 21.

Here are a few regarding the problem associated with inadequate tear
exchange in some patients (post-lens tear film). It is important to
realize that this is nearly in all cases related to EW (i.e., this is
not a significant problem with DW on SHCLs):

o Guillon M, Maissa C: Tear exchange -- Does it matter? Optician
Dec 1999 No. 5378 Vol. 218. p29-30.

o http://tinyurl.com/rzgkk

"The PoLTF is the tear layer between ocular surface and
contact lens back surface. It is made up of a thin aqueous
phase (1µm) and of a compressed mucin phase (30-40µm). The
mucin phase is of unknown thickness but it is probably at
least marginally thinner than the pre-ocular tear film. The
maintenance of the integrity of the mucin layer is essential
to safe contact lens wear. The maintenance of the aqueous
phase is essential to controlling the viscosity of the PoLTF
and facilitating the elimination of back surface debris. The
closed eye wearing period with it's associated aqueous
depletion and reduced lens movement produces the most
challenging phase in EW. The period immediately upon eye
opening is therefore the key recovery phase when PoLTF aqueous
replenishment takes place.

Regarding silicone hydrogels, the following clinical practice
is recommended:

Follow-up visits should take place in the morning and include
the evaluation of the PoLTF and the assessment of lens
movement.

Patients should be instructed to carry out self-evaluation of
lens binding upon waking.

Non-viscous eye drops such as saline (preferably single dose
eye drops) should be dispensed for use upon waking."

o http://tinyurl.com/ojxtt

[...]
"Chapter 4 by Michel Guillon and Cécile Maissa addresses one
of the remaining clinical concerns with silicone hydrogel
lenses: tear exchange. An important ocular defence mechanism
is blinking and tearing, and much of the effectiveness of this
system is lost when contact lenses are worn on a continual
basis. The authors note that rigidity with silicone hydrogels
is much greater than with conventional lens materials and that
this causes a relatively high ‘squeeze pressure’ in the
mid-periphery and which can also mean that the fit of the lens
is more closely related to the lens parameters than
conventional soft lenses. A review of both fluid exchange and
particle exchange data causes the authors to recommend the
clinical examination of post lens debris soon after eye
opening when silicone hydrogels are worn."
[...]

I have read quite a few articles in Review of Optometry, Optometric
Management, Contact Lens Spectrum, etc. regarding the above also.

Quote:
You are fortunate that your patients haven't experienced these.

Yes, I am.

And, to think of it, I haven't experienced them with Oasys, probably
because I don't fit it as much as other Si-Hy CLs.

Well, I started using Purevision quite heavily in 1999, and then
switched to Focus N&D of necessity. I've used them all.

I'm not saying there isn't room for improvement. But, I've been taking
symptomatic patients out of their hydrogels and putting them into
silicone-hydrogels for so long now, and with such stellar results, that
nobody can convince me that they are by far the better option for most
SCL wearers.

I did not say that. Haven't you been paying attention?

Silicone Hydrogel contact lenses are my SCL lens of choice in 07/2006.
They are far and away superior to HEMA based lenses in the vast
majority of patients, primarily because of their increased oxygen
permeability and their reduction of symptomology in my dry-eyed
patients. I love them and have written as much in several posts here.
Got it?

That being said, in quite a few patients, they deposit easier than
their HEMA lenses did, so that the SHCLs become uncomfortable quicker,
need to be changed more often, or require more cleaning than their old
HEMA lenses did. These "quite a few patients" are those whose HEMA
lenses were very dirty at 2 weeks and ready to be thrown away; one
patient in particular didn't even get 3 days of wear where she could
get 2 weeks (but no more) of wear with her HEMA lenses.

Additionally, in quite a few patients, because of inadequate tear
exchange (stagnation in the post-lens tear film) compared to their old
HEMA lenses, successful EW HEMA wearing patients can develop
CLARE/bacterial keratitis when moved to SHCL.

IOW, in my experience, SHCLs need to be fit looser and with more
movement than their HEMA counterparts for successful EW in these
particular patients.

How dooes a doctor know which of these EW patients are gonna be
problematic? You don't have a priori knowledge, but it happened
enough with me to make sure I fit SHCLs as loose as comfort will allow
for my EW patients.
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Anon E. Muss
medicine forum Guru Wannabe


Joined: 22 May 2006
Posts: 136

PostPosted: Wed Jul 19, 2006 12:11 am    Post subject: Re: si hy lens experiences Reply with quote

On 18 Jul 2006 04:25:29 -0700, "Dr. Leukoma" <drg@leukoma.com> wrote:

Quote:
Anon E. Muss wrote:


You are fortunate that your patients haven't experienced these.

And, to think of it, I haven't experienced them with Oasys, probably
because I don't fit it as much as other Si-Hy CLs.

What on earth are you fitting?

Ciba O2Optix, Ciba Focus Night & Day, Acuvue Advance and Acuvue Oasys,
in that order of preference. I only fit Oasys on patients that it
moves well on; and for me, that is patients with Ks >46.00 for the
most part.

Quote:
I sometimes go weeks without fitting a single HEMA lens, with the
possible exception of Proclears or XC.

I have too many patients with high astigmatism wearing Coopervision's
Hydrasoft Torics to make that claim.

Quote:
A revolution in contact lens fitting practices IS occurring out there.

Quit preaching to the choir.
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Dr. Leukoma
medicine forum Guru


Joined: 30 Apr 2005
Posts: 1283

PostPosted: Wed Jul 19, 2006 2:14 am    Post subject: Re: si hy lens experiences Reply with quote

Anon E. Muss wrote:
Quote:
On 18 Jul 2006 04:25:29 -0700, "Dr. Leukoma" <drg@leukoma.com> wrote:

Anon E. Muss wrote:


You are fortunate that your patients haven't experienced these.

And, to think of it, I haven't experienced them with Oasys, probably
because I don't fit it as much as other Si-Hy CLs.

What on earth are you fitting?

Ciba O2Optix, Ciba Focus Night & Day, Acuvue Advance and Acuvue Oasys,
in that order of preference. I only fit Oasys on patients that it
moves well on; and for me, that is patients with Ks >46.00 for the
most part.

Wow, that's surprising. You should fit more Oasys. Oasys moves quite
well. It does move less because it has a lower elastic modulus as well
as a super-edge, but it does move enough, IMO.
Quote:

I sometimes go weeks without fitting a single HEMA lens, with the
possible exception of Proclears or XC.

I have too many patients with high astigmatism wearing Coopervision's
Hydrasoft Torics to make that claim.

May I introduce you to Gelflex custom torics, made from hioxifilcon B
material?
Quote:

A revolution in contact lens fitting practices IS occurring out there.

Quit preaching to the choir.

Sounded like a bunch of grouses to me. :)

DrG
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