Home | Contact Us | FAQ | Search & Site Map | Link to Us
Sign In | Join | Other 45 Sites in Network
Home
Discussion Groups
General
GeneralCardiologyVisionDentistryPharmacyLaboratoryNutritionAlternative
Diseases and Disorders
AIDSAlzheimer'sArthritisAsthmaCancerBreast CancerDiabetesEpilepsyGlaucomaHepatitisHerpesLupusProstate BPHProstate CancerProstatitisSinusitisTinnitus

Medical Forum / General / Vision / January 2007

Tip: Looking for answers? Try searching our database.

Question for Dr. Stacy Regarding Floaters

Thread view: 
Enable EMail Alerts  Start New Thread
Thread rating: 
Charles Braverman - 28 Dec 2006 23:12 GMT
Dr. Stacy,

In a recent discussion regarding floaters (which I unfortunately deleted), I
believe you stated that floaters would have to be VERY bad before a
vitrectomy might be justified.

I have what I consider to be very bad floaters for the past 7 years, and
have been wrestling with that question over that time.

What criteria does one use to determine whether to seek a vitrectomy? In my
case, I have large globs of "mud" that obscure a large portion of my vision.
Reading is very difficult, for example, not only because so much of a line
of print is obscured, but because the contrast between the print and
background is poor.  It is also not an exaggeration to say that the globs
torment me almost all of the time and seem to cause persistent eye strain
and tearing.  Yet I have something close to 20/20 on an eye chart and no eye
disease according to recent dilated eye exams.  What are your thoughts as to
what criteria justify vitrectomy?

Thank you for your comments.

I would also be interested in any additional opinions from other readers.

Charles
Dan Abel - 28 Dec 2006 23:58 GMT
> In a recent discussion regarding floaters (which I unfortunately deleted), I
> believe you stated that floaters would have to be VERY bad before a
> vitrectomy might be justified.

Google is your friend.

> and tearing.  Yet I have something close to 20/20 on an eye chart and no eye
> disease according to recent dilated eye exams.  What are your thoughts as to
> what criteria justify vitrectomy?

20/20 on the eye chart is a first cut.  It isn't the final answer.

> I would also be interested in any additional opinions from other readers.

What does your doctor advise?  

ObOT:  I had a vitrectomy about a year ago.  My doctor said that as a
side effect, I would lose the floaters.
Jane - 29 Dec 2006 00:12 GMT
Charles, if I were in your situation, I'd be setting up a pre-surgery
consultation with my retinal surgeon rather than seeking opinions on
the internet.  I had a vitrectomy about a year ago to remove a macular
pucker.  The worst consequence of the surgery was the development of a
cataract in the surgical eye.  (I've read that it's the result of the
lens' exposure to oxygen.)  Unless you are at high risk for retinal
detachment,  I believe that the a vitrectomy is quite safe if done by a
competent retinal surgeon.  And with the new 25-gauge "sutureless"
equipment, recovery is very rapid.  One surgeon wrote that the day
after the vitrectomy, it's frequently difficult to tell which of the
patient's eyes had the surgery.

Best of luck!
William Stacy - 29 Dec 2006 02:24 GMT
Good advice, but since he's asking, I'll venture that he might be a
candidate for it, especially if he is over age 50, since the subsequent
cataract surgery that is certain to follow if he hasn't yet had it is
sort of a blessing in disguise.  I'll bet he's 20/20 only part of the
time, and when the goop is in the way he may drop to worse than 20/100
or so in the affected eye.

w.stacy, o.d.

>Charles, if I were in your situation, I'd be setting up a pre-surgery
>consultation with my retinal surgeon rather than seeking opinions on
[quoted text clipped - 11 lines]
>
>  
Anon E. Muss - 29 Dec 2006 16:07 GMT
>Dr. Stacy,
>
[quoted text clipped - 18 lines]
>
>I would also be interested in any additional opinions from other readers.

First of all, realize a vitrectomy is not "minor surgery".

Next, realize that anytime the eye gets "cracked open" there is real
risk of a microbial infection inside the eye (i.e., endophthalmitis).

I have never referred a patient to a retinal surgeon for an evaluation
for vitrectomy to get rid of floaters.  However, my criteria for a
"20/20 patient" would be the patient would to have to be absolutely
miserable and thoroughly understand the risks/benefits of the
procedure.  From your description (i.e., "torment") above, you may be
better off being prescribed an antidepressant than a vitrectomy.

And although some others have said recovery from a vitrectomy is
minimal, there are other times after a vitrectomy that your eye feels
like someone played pinball with it.
Dan Abel - 29 Dec 2006 16:56 GMT
> >I would also be interested in any additional opinions from other readers.
>
[quoted text clipped - 13 lines]
> minimal, there are other times after a vitrectomy that your eye feels
> like someone played pinball with it.

Mine went quite well.  However, I was on restriction for two weeks (no
lifting or bending over).  Since I had already given notice at work, and
had planned to spend the next week cleaning out my office, this was a
problem.  I talked to my boss and extended my leaving another two weeks.  
This was a good thing, since I had over a hundred days of sick leave, so
I spent two weeks at home at full pay.
Jane - 29 Dec 2006 18:56 GMT
My vitrectomy was done with the older 20-gauge equipment, which
required sutures.  One day post-op my eye was practically swollen shut
and bright red.  I looked terrible, although it wasn't painful.  I
later developed a severe suture reaction, which was reportedly related
to the (mis)placement of the sutures (put in by a resident who--in my
opinion--didn't know what he was doing.)  This left an unsightly red
mound on the white of my eye that lasted for weeks.

But happily, surgery with the newer 25-gauge "sutureless" equipment
inflicts no such torture on the patient.  I believe the surgery time is
quicker, and recovery is reported to be faster and painless.  I believe
that Charles has a lot to gain from the procedure and should certainly
schedule a consultation with the best retinal surgeon in his area.
(This does not require a referral from an optometrist.)

I haven't kept up with my reading in the area of retinal surgery.
However, I do know that just a few years ago a vitrectomy was not done
to remove a macular pucker until vision was worse than 20/60.  Today,
with better equipment and technique, some surgeons will operate on a
patient with 20/20 vision if the distortion from the pucker is
bothersome.  I also believe that vitrectomies for floaters are
performed more frequently today than in the recent past.
William Stacy - 29 Dec 2006 19:50 GMT
I think the chance of endophthalmitis is pretty small, given modern day
procedures and antibiotics.  And I think that "cracked" is a poor choice
of words to use with someone who is not familiar with the procedure,
where 3 very small holes are cut in the eye
for the instrumentation.  It is minor in that the patient is usually not
under deep anesthesia, and intubation of the trachea is usually not
needed.  I think vitrectomies for major vitreous opacities is becoming
more common, as it is quite successful.  This person should indeed
consult a vitreous surgeon before consulting a psychiatrist.

w.stacy, o.d.

>  
>
[quoted text clipped - 38 lines]
>like someone played pinball with it.
>  
Anon E. Muss - 29 Dec 2006 21:58 GMT
>And I think that "cracked" is a poor choice of words to use with
>someone who is not familiar with the procedure, where 3 very small
>holes are cut in the eye for the instrumentation.

The euphemsm was used to make the point was that vitrectomy is
*intraocular* surgery, like cataract surgery or refractive lensectomy,
not extraocular surgery like LASIK or PRK.

When an entry point into the eye is made -- even for transconjuctival
sutureless 25-gauge pars plana vitrectomy (PPV) -- new sets of risks
are involved.

And don't even ask what would happen if a pars plana approach fails
and they perform "Open Sky" vitrectomy.

>I think vitrectomies for major vitreous opacities is becoming more
>common, as it is quite successful.

I think it is likely there is a very good reason his ECPs apparently
hasn't referred him to a retinal surgeon for a vitrectomy eval after 7
years of "very bad floaters".

However, if only for his mental health, I would obtain vitreo-retinal
consultation for this gentleman.
Jane - 30 Dec 2006 00:19 GMT
According to a June '06 article on emedicine.com, postoperative
endophthalmitis is a rare complication of intraocular surgery.   Data
from Bascom Palmer  from '84 to '94 show that only  0.05% of patients
developed endophthalmitis after pars plana vitrectomy.  (The rate was
0.08% for patients undergoing cataract extraction.)

Even with the older 20-gauge equipment, having a vitrectomy is not a
painful ordeal.  My surgery was done at a teaching hospital with local
anesthesia alone.  (I opted to skip the sedation.)  I experienced no
pain during the surgery and was actually able to see the instruments in
my eye and follow the action.  (A fascinating and hopefully
once-in-a-lifetime experience.)  After the surgery  (with one eye
patched), I had lunch and then walked over to the local multiplex,
where I stayed for a double feature.  My vision improved from 20/50 to
20/20 during the weeks that followed.

You guys really perform a valuable service for us nonprofessionals by
posting info on this web site.  But I really disagree with you in this
case, Anon E. Muss, and your comment about antidepressant medication is
a little offensive.  Have some empathy--how would you feel living your
life with the types of problems that Charles has been experiencing?
Anon E. Muss - 30 Dec 2006 00:50 GMT
>But I really disagree with you in this case, Anon E. Muss, and your
>comment about antidepressant medication is a little offensive.

The OP wrote, quote:

    "I have what I consider to be very bad floaters for the past 7
    years"

    "It is also not an exaggeration to say that the globs
    torment me almost all of the time and seem to cause persistent
    eye strain and tearing"

It is not unreasonable to recommend for someone who has been tormented
almost all the time for the past 7 years for whatever reason to
undergo a psychiatric evaluation.

Even more so when the objective findings (i.e., 20/20 vision with no
eye pathology) do not concur with his subjective complaints (i.e.,
torment).
William Stacy - 30 Dec 2006 01:32 GMT
20/20 is a subjective finding, not an objective one.  And floaters
notoriously cause 20/20 vision to drop to 20/100 or worse as the floater
passes over the macula.

w.stacy, o.d.

>Even more so when the objective findings (i.e., 20/20 vision with no
>eye pathology) do not concur with his subjective complaints (i.e.,
>torment).
>  
William Stacy - 30 Dec 2006 01:34 GMT
I should rephrase that:  "large floaters notoriously CAN cause 20/20
vision to drop to 20/100 or worse as the..."

> 20/20 is a subjective finding, not an objective one.  And floaters
> notoriously cause 20/20 vision to drop to 20/100 or worse as the
[quoted text clipped - 5 lines]
>> torment).
>>  
Anon E. Muss - 30 Dec 2006 04:25 GMT
>20/20 is a subjective finding, not an objective one.

Quick answer:  In the standard SOAP format for medical records, visual
acuity is recorded in the "O" section for (O)bjective.

Longer answer:  When a patient's visual acuity is properly tested
using a wallchart with a patient who is being honest and giving proper
effort, I consider that to be an objective record of his visual acuity
unless proven otherwise.

No, it's NOT *purely* an objective test of visual function like a
visual evoked potential (VEP), optokinetic response (OKN), functional
magnetic resonance imaging (MRI) or a pattern electroretinogram
(pERG).  Yes, people can lie, not give good effort, can be hysterical,
malinger or have otherwise non-physiologic loss of visual acuity.

But performed properly with a patient who is honestly trying and
giving his best effort, it is, in my book, an objective test of his
visual function.  It should be measurable, repeatable and consistent.
It's part of the art of being a doctor that allows one, generally, to
determine whether to believe in the objectivity of the test results.

When someone says they can read those 20/20 letters, but they are
"fuzzy", "dim", "clear", etc., then that is a subjective response.

In the same way, I consider a confrontation visual field that clearly
demonstrates a total homonymous hemianopia to be essentially
objective.  And whether it is performed by confrontations, a tangent
screen, kinetically via Goldmann perimeter, a Matrix FDT or automated
via an Octopus 101, it's still gonna be there.  The exact extent will
vary from test to test and is influenced by a person's subjectivity,
but an person educated in interpreting visual fields will clearly be
able to see it's there each and every time.

I consider extraocular motilities to be objective even though people
can fake those too.

Maybe this will help:

I consider anything which is a "sign" to be "objective" even if it
requires some sort of patient response or interpretation:  Loss or
presence of normal snellen visual acuity, clear cut visual field
defects (e.g., homonymous hemianopia), restriction on extraocular
motilities, abnormal color vision plate test result, cover/uncover
test results, acquired torsional nystagmus, absence of stereoacuity,
positive photostress test, exophthalmometry, clear cut "red cap
desaturation test"/afferent pupillary defect.

I consider anything which is a "symptom" or complaint to be
"subjective":  Vision is clear/blurry, can't see off to one side,
can't move my eyes to the right, hard to tell difference between navy
blue and purple socks, eyes cross, vision shakes, can't thread a
needle, can't see for a long time after car headlights blast me at
night, eyes bug out, colors/lights seem dim out of my one eye.

P.S.  Got a pachymeter about a month ago.  :)
William Stacy - 30 Dec 2006 20:03 GMT
>>20/20 is a subjective finding, not an objective one.
>
> Quick answer:  In the standard SOAP format for medical records, visual
> acuity is recorded in the "O" section for (O)bjective.

Once again I disagree with the "standard" then.  Acuities and
*subjective* refraction data belong together in the SUBJECTIVE area.
Retinoscopy and auto-refractions belong in the OBJECTIVE area.

> Longer answer:  When a patient's visual acuity is properly tested
> using a wallchart with a patient who is being honest and giving proper
> effort, I consider that to be an objective record of his visual acuity
> unless proven otherwise.

But you cannot determine the degree of "honest and proper effort".
That's why it's so variable and subjective.

> No, it's NOT *purely* an objective test of visual function like a
> visual evoked potential (VEP), optokinetic response (OKN), functional
> magnetic resonance imaging (MRI) or a pattern electroretinogram
> (pERG).  Yes, people can lie, not give good effort, can be hysterical,
> malinger or have otherwise non-physiologic loss of visual acuity.

Nor can you ALWAYS tell if they are hysterical or malingering.

> In the same way, I consider a confrontation visual field that clearly
> demonstrates a total homonymous hemianopia to be essentially
[quoted text clipped - 4 lines]
> but an person educated in interpreting visual fields will clearly be
> able to see it's there each and every time.

I also put these in the subjective realm.

> I consider extraocular motilities to be objective even though people
> can fake those too.

Fake a strabismus?  Or more important, fake orthophoria when the patient
is a strab?  I think not.  But obviously these are objective, as we are
making direct OBSERVATIONS by definition.  OTOH, things like phorias and
fixation disparity measurements are just as obviously subjective items.

> Maybe this will help:
>
[quoted text clipped - 6 lines]
> positive photostress test, exophthalmometry, clear cut "red cap
> desaturation test"/afferent pupillary defect.

Some of those are signs, some are symptoms.  You're lumping them
together, I think unnecessarily and confusingly.

> I consider anything which is a "symptom" or complaint to be
> "subjective":  Vision is clear/blurry, can't see off to one side,
> can't move my eyes to the right, hard to tell difference between navy
> blue and purple socks, eyes cross, vision shakes, can't thread a
> needle, can't see for a long time after car headlights blast me at
> night, eyes bug out, colors/lights seem dim out of my one eye.

Agreed with those, if reported by the patient and not observable (eyes
bug out should easily be observable as exophthalmos or proptosis).

> P.S.  Got a pachymeter about a month ago.  :)

A very good objective test, don't you think?  I'll bet you're using it
more than you used to "order it" from your glaucoma guy?  I had a nice
exchange with a lecturer at the Monterey Symposium in which he asked for
a show of hands as to who was "modifying goldmann readings" by the
pachymeter.  I was about the only one to raise my hand.  He challenged
me and I said I do it in my head, not on paper.  Helps me get a feel of
what's going on. He then explained patiently that my correction tables
are not all that accurate.  I patiently explained to him that in most
aspects of medicine even variable or imperfect corrections are better
than no corrections at all.  Love to make those guys squirm.  He allowed
that it was a good point.

w.stacy, o.d.
Anon E. Muss - 31 Dec 2006 07:31 GMT
[snip]

>Once again I disagree with the "standard" then.

No use debating with you about it then.

>> I consider extraocular motilities to be objective even though people
>> can fake those too.
>
>Fake a strabismus?  Or more important, fake orthophoria when the patient
>is a strab?

Not cover/uncover test, but extraocular motilities.  You know --
checking for a full range of motion with no gaze restrictions.  These
can be "faked".

>> P.S.  Got a pachymeter about a month ago.  :)
>
>A very good objective test, don't you think?

It is (however, the fundus camera we recently got is much more
useful.)

I always recommend measuring central corneal thickness (CCT) for all
ocular hypertensive patients (i.e., <22.5mm Hg per uncorrected
Goldmann applanation tonometry [GAT]) per the OHTS recommendations,
glaucoma suspects (e.g., those with suspicious optic nerves, retinal
nerve fiber layer defects, drance hemorrhages, strong family history,
etc.) and definite glaucoma patients.

>I'll bet you're using it more than you used to "order it" from your
>glaucoma guy?

Indeed I am.

BTW, I never ordered it from a "glaucoma guy".

I obtained CCT measurements, objective retinal nerve fiber layer
analysis (i.e., GDx VCC or Stratus OCT), objective optic nerve
analysis (i.e., HRT3) and optic nerve photographs on all my glaucoma
patients/suspects from the special testing clinic at SCCO.

Now that I have a pachymeter and a fundus camera, I do that in house
but still turf out the imaging to SCCO.  I do wish they'd get an
Octopus 101 in addition to the HFAs they have there.

BTW, it works out great.  Future ODs (students) get exposed to
glaucoma patients, patients get access to cutting edge diagnostic
technology, I know I'm getting the testing I ordered done and my
patients sent back to me versus always wondering with the OMD, I'm
comfortable with the ODs there (for the most part) and I don't have to
worry about expensive lease payments on still evolving technology.

>I had a nice exchange with a lecturer at the Monterey Symposium in
>which he asked for a show of hands as to who was "modifying goldmann
[quoted text clipped - 5 lines]
>imperfect corrections are better than no corrections at all.  Love to
>make those guys squirm.

Too bad you weren't at the Academy this year and didn't get the chance
to try and make Murray Fingeret, Harry Quigley and David Friedman
squirm during their glaucoma lecture.  Heh.

The Ziemer Ophthalmic rep (maker of the Pascal Dynamic Contour
Tonometry [PDCT]) said they've done a ton of testing comparing GAT to
PDCT in conjunction with CCT.  They said that when a cornea is thin,
the GAT usually, but not always, reads low.  However, they said that
when a cornea is thick, there was no clear trend -- it could be lower,
higher or unchanged versus PDCT.

And hence the problem with adjusting IOPs based on CCT -- you just
don't know if the adjustments you are making are accurate.  Per the
Ziemer rep, a patient with a GAT reading of 19 and a CCT of 595 could
have just as much a chance of having a "real" IOP of 23 as 17.  And
the patient with a GAT reading of 17 and a CCT of 515 might have a
"real" IOP of 18 or 23 -- you just don't know.  Both Goldmann and
these adjustment algorithms are inprecise and "noisy" and when you
compensate you are IMHO losing more in "noise" than you are gaining in
terms of diagnostic info.

(The "21" or "22.5"mm Hg cutoff for OHTN is arbitrary too -- it's
based on old data that said "21" was 2 standard deviations above the
average.  Those numbers don't come from any well-designed studies --
they were literally pulled out of the air.)

One thing we know with a high degree of certainty is that if you are
an OHTN (per uncorrected GAT readings) and have thin corneas, your
risk of developing glaucoma within 5 years is considerably higher than
if you have thick corneas.

Another thing we know is that when one is developing progressive
glaucomatous optic neuropathy, the only proven way to lower the risk
of continued progression is to lower the IOP.

In other words (IOW), it's not so important what a particular person's
exact IOP is (within reason) as far as saying this person does or
doesn't have glaucoma -- more important is if someone has
unquestionably progressive glaucomatous optic neuropathy, their IOP
isn't consistently low enough for their optic nerve (i.e., their optic
nerve is too sick/weak to tolerate that particular IOP) and the IOP
needs to be lowered.

Of course, this "need" needs to be looked at in the context of the
estimated rate of progression, the patient's estimated life span and
the impact on the patient's qualty of life with treatment versus not
treatment.  There is a great article by George Spaeth et al (Surv
Ophthalmol. 2006 Jul-Aug;51(4):293-315.) discussing this very issue in
combination with his "Disc Damage Likelihood Scale" he helped develop
(see <http://tinyurl.com/vzhyy>).  It's a little complex and
overwhelming for the private practitioner to implement I think, but
the ideas and foundation are quite strong.

In summary, I don't think by compensating for IOPs that you are
obtaining more valuable diagnostic data than I do when I measure CCTs
and merely label those OHTN patients with thin corneas and having an
additional risk factor and those with thick corneas as having a
protective risk factor.  And that goes along with the general
consensus of glaucoma experts.

Far better IMHO to go on what the OHTS study said -- thin CCTs are a
strong predictory risk factor in OHTN patients that developed glaucoma
(see <http://tinyurl.com/vlc22>).

Deja vu.  I think we've discussed this before.
LarryDoc - 31 Dec 2006 20:56 GMT

> In summary, I don't think by compensating for IOPs that you are
> obtaining more valuable diagnostic data than I do when I measure CCTs
[quoted text clipped - 8 lines]
>
> Deja vu.  I think we've discussed this before.

Indeed.  But thanks for taking the time to so concisely present the
issue. This is precisely what the glaucoma specialists in my
neighborhood live by and that which most of us have come to accept as
valid rationale for the diagnosis and management.  At least for now.

But on another, possibly related issue:
What of the thousands of LASIK's/PRK'd people with now thin corneas?  
Might they have to classified as higher risk glaucoma suspects?  Do thin
corneas alone predict risk or is there an underlying genetic cause that
relates simultaneously to thin cornea and glaucoma?  Inquiring
minds........

LB, O.D.
(rarely seen around these parts these days)
Anon E. Muss - 01 Jan 2007 02:40 GMT
>But on another, possibly related issue:
>What of the thousands of LASIK's/PRK'd people with now thin corneas?  
>Might they have to classified as higher risk glaucoma suspects?

Not at this time -- there is absolutely no evidence that I am aware of
that iatrogenically thinned corneas (ITC) increase the risk of
developing glaucoma any more than performing full-thickness
penetrating keratoplasty with a "thick" donor graft would be
"glaucomaprotective".

The important thing to realize is that the applanation/indention
tonometry readings you get on ITC will almost certainly be more
inaccurate than ever.  And all the "conversion tables" used as far as
I know are based on natural corneal thicknesses, not iatrogenically
altered ones.

Therefore, you really have no idea how much your readings are off
here.  I believe it is very fair to assume that your Goldmann
applanation readings (GAT) will be falsely low.  How low?  It's not
real clear.

So what do I do in situations like this?

[Well, it's like patients I have with tilted discs; in those patients,
I rely a lot more on looking at the fields, the optic nerve
(ONH)/retinal nerve fiber layer (RNFL) imaging and the IOP.  Or it's
like the patients I have that are horrible at taking visual fields; in
those patients, I put more weight on the ONH/RNFL imaging, the optic
nerve appearance, the retinal nerve fiber layer and the IOP.]

I really pay more attention to the perimetry results, the imaging
results and the fundus appearance -- realizing that the IOP reading is
not going to be all that accurate, but reasonably assured it will be
precise (see <http://tinyurl.com/y4yglp> under the section "Accuracy
vs precision - the target analogy").

The Ziemer ophthalmic guys say their Pascal Dynamic Contour Tonometer
(PDCT) is great for situations like this -- actually, they say it's
great for everybody and accurate/precise -- but at around $4K a pop
I'm still waiting.  I've talked to some people who are commonly
considered to be glaucoma experts in the Optometric community and
their opinions are mixed -- some thing it's useful, others told me
they aren't so sure it's precise.

What the PDCT guys need to remember is that our treatment of glaucoma
is based on many years where GAT was (and still is) the "gold
standard" for IOP measurement.  And what we should realize is, and I
wrote about this earlier in the thread, knowing the exact IOP may not
be all that crucial in the vast majority of glaucoma cases.  What we
really need is a test that is *precise* (i.e., "off" consistently by
the same amount) from visit to visit, because one of our barometers in
glaucoma treatment is IOP lowering.  In other words (IOW), when we
measure IOP, it may not be as important to know whether the IOP really
was "23" before treatment and now it is really "17", rather what is
important is that the knowledge that we *really have* lowered the IOP
by ~25% is reliable.  We believe the GAT is precise (enough).

I write this in light of the fact the many people with ocular
hypertension (OHTN) never develop glaucoma and the many people with
IOPs never measured <22mm Hg that develop glaucoma.  Precision may be
a lot more important than accuracy, though in a perfect world, we want
a device that is both.

>Do thin corneas alone predict risk or is there an underlying genetic
>cause that relates simultaneously to thin cornea and glaucoma?

The general consensus of glaucoma experts I have spoken to and read
articles from believe that central corneal thickness (CCT) is an
indirect measurement of something else that is the real risk factor.

Interesting tidbit:

I didn't know this until the 12/2006 Academy meeting, but Harry
Quigley informed the audience that CCT even being measured in the
Ocular Hypertension Treatment Study (OHTS) was only in there because
one ophthalmologist (OMD) at UC Davis (I don't think he mentioned this
doctor by name, but I believe it is James Brandt) strongly wanted it
in there.

Interestingly, this same OMD -- the one that lobbied to have CCT
measured in the OHTS -- argues *against* adjusting IOPs based on CCT
readings in the 12/01/2006 issue of "Ocular Surgery News" (see
<http://tinyurl.com/y7sq42>) and gives his rationale for such
recommendation -- important quotes:

    “Pachymetry over the past few years has come of age with the
    recognition that corneal thickness is a very big issue in the
    accuracy of measuring IOP and the assessment of risk in our
    glaucoma patients,” Dr. Brandt said. “If you have a patient
    with a thin cornea and higher pressures, that individual is at
    much higher risk of developing glaucoma than somebody with the
    same IOP but a thicker cornea.”

and

    Because of the inherent error in Goldmann measurement, he
    suggested, it is of questionable value to adjust a patient’s
    Goldmann IOP by using a nomogram based on corneal thickness.

    “You are kidding yourself if you try to apply an algorithm to
    adjust by a few millimeters of mercury the underlying
    measurement, which is imprecise,” Dr. Brandt said.

Bs pbhefr, guvf jba'g pbaivapr Ovyy Fgnpl :)

P.S.  To be fair, there are some that do advocate IOP adjustment based
on CCT such as Leon Herndon in a recent article in "Ophthalmology
Times" (see <http://tinyurl.com/szjy2>), but they are definitely in
the minority.  However, in this same article in Ophthalmology Times
James Brandt again counters with a far more (IMHO) compelling
argument.
Anon E. Muss - 01 Jan 2007 02:49 GMT
[snip]

>Interestingly, this same OMD -- the one that lobbied to have CCT
>measured in the OHTS -- argues *against* adjusting IOPs based on CCT
>readings in the 12/01/2006 issue of "Ocular Surgery News" (see
><http://tinyurl.com/y7sq42>) and gives his rationale for such
>recommendation -- important quotes:

[snip]

>    “You are kidding yourself if you try to apply an algorithm to
>    adjust by a few millimeters of mercury the underlying
>    measurement, which is imprecise,” Dr. Brandt said.

I believe he meant "inaccurate".  :)
William Stacy, O.D. - 01 Jan 2007 18:00 GMT
> I write this in light of the fact the many people with ocular
> hypertension (OHTN) never develop glaucoma and the many people with
> IOPs never measured <22mm Hg that develop glaucoma.

Given the context of your post, I think you meant never measured >22.

w.stacy, o.d.
Anon E. Muss - 01 Jan 2007 19:09 GMT
>> I write this in light of the fact the many people with ocular
>> hypertension (OHTN) never develop glaucoma and the many people with
>> IOPs never measured <22mm Hg that develop glaucoma.
>
>Given the context of your post, I think you meant never measured >22.

How's this?

A lot of people with consistently "high" IOP never develop glaucoma
and a lot of people with consistently "low" IOP do develop glaucoma.

As a result, IOP measurement is a very poor method of screening
glaucoma patients from normals in the vast majority of the population.
William Stacy, O.D. - 01 Jan 2007 19:44 GMT
>>>I write this in light of the fact the many people with ocular
>>>hypertension (OHTN) never develop glaucoma and the many people with
[quoted text clipped - 9 lines]
> As a result, IOP measurement is a very poor method of screening
> glaucoma patients from normals in the vast majority of the population.

Agreed, it's just that your quote translates:  "many people with iops
never measured "LESS THAN 22mm Hg develop glaucoma."  That statement is
certainly true, although it would be more meaningful to have said "most
people who never measured less than 22mm Hg have glaucoma".

But what I think you were trying to say was what I originally answered
above.

It's kind of a pet peeve of mine, like when people specify + when they
meant - in an Rx.  Or when the order says "DNR" when the patient is not
terminal.  Little things like that sometimes are important.

w.stacy, o.d.
 
Sign In
Join
My Latest Posts
My Monitored Threads
My Blog
My Photo Gallery
My Profile
My Homepage

Start New Thread
Enable EMail Alerts
Rate this Thread



©2009 Advenet LLC   Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.