From: Reflections
on Central Corneal Thicknesses Volume 6-3, 2005
By Douglas Anderson
The Ocular Hypertension Treatment Study
“It has since [the publication of the OHTS] been debated whether
thin corneas predict the risk only because the IOP is underestimated
by tonometry when the cornea is thin or additionally because
a thin cornea represents a general weakness of ocular support
structures that make the eye more vulnerable to harmful effects
of IOP.”
“Corneal thickness does not over-ride or eliminate other features
of the case that may lead you to an estimate of risk, but simply
increases or decreases your estimate based on other factors.”
M & T Commentary:
Just as with the “glaucoma scanning devices,” no single test
or parameter confers or refutes the diagnosis of glaucoma,
but they all are cerebrally coalesced by an astute clinician
to make sound clinical judgments.
Examining the Evidence
“If we believe from the OHTS data that support structures of
the optic nerve are weak in eyes with naturally thin corneas,
it would not be expected that the structure of the optic
nerve would be affected by acquired alteration of the corneal
thickness. For example, if the cornea is thin by virtue
of LASIK, the optic nerve is not made weaker, nor is it stronger
if the cornea is thickened by edema or by scarring. Such
acquired corneal changes may affect the tonometric readings,
but not the sturdiness of the optic nerve.”
M & T Commentary:
This myth of “LASIK-induced glaucoma” has confused some people,
but this nicely explains the situation.
Using the Reported Evidence and Concepts
“The CCT [central corneal thickness] may moderate your assessment
of risk in conjunction with age, level of tonometer reading,
family history, and other factors you feel affect the patient’s
risk.”
“The evidence that corneal thickness affects the rate of further
glaucomatous damage is not as firm for cases of glaucoma as
it is for ocular hypertension. Until we know more, the severity
of existing damage, family history, and age likely remain the
main guides to choosing a percentage of pressure of IOP lowering
you would like to achieve.”
“It may also be noted that risk assessment at the time that
either ocular hypertension or glaucoma is first discovered
is not the same as assessing the risk of the patient who has
been monitored for several years. As time goes on, the clinical
course to date gradually takes an increasingly dominant role
in risk assessment and decision making. Therefore, if the
eye shows progressive cupping or field loss at an unacceptable
rate, the decision to lower the pressure is unaffected by CCT.
Similarly, long term stability may be taken as evidence of
adequate treatment, no matter how thick or thin the cornea
may be.”
Summary
“CCT has been identified as a contributing predictive factor
for glaucoma development in cases of recently discovered
ocular hypertension. The basis for its ability to predict
(inaccurate tonometry or weakness of ocular structures) is
not known. “
“Often the known clinical course to date is the dominant
feature that guides therapeutic decisions in establishing
glaucoma, so CCT measurements are typically not helpful,
but there are individual cases in which knowing the CCT is
very helpful. Before obtaining CCT, one should therefore
stop to consider whether the information will assist in making
a clinical decision in this particular patient, just as we
should for any examination or test we contemplate obtaining.
For some patients with ocular hypertension or glaucoma, knowing
the CCT will affect the clinical decision, but for others,
not.”
M & T Commentary:
In the June, 2005 issue of “Eyeworld (page 28), this issue
was addressed. Here are a few quotes: “there is value in
knowing the corneal thickness with established glaucoma where
the decision to treat has already been made. This doctor
said she, ‘finds it most useful in patients who seem to be
progressing but whose IOP seems reasonably well controlled.’
In these patients, she often encounters unexpectedly thin
corneas, and she revises her target IOP downward. "There
are a few patients who may not need [pachymetry], such as
patients with stable glaucoma whose optic nerve and visual
field status have remained unchanged for years are unlikely
to benefit from the measurements.” While we agree with these
perspectives, we vote to keep life simple and consistent;
i.e., every glaucoma suspect, and every patient with glaucoma
should have their corneal thickness measured and properly
annotated in the chart.
From: Interpreting Relative Risks and Possible Implications
for the current ‘Mantra’: 10% Risk Reduction for Every Millimeter
IOP Reduction
by Ravi Thomas, et. al.
“The NNT [number needed to treat] reflects the number of
patients we need to treat in order to obtain one benefit or
desirable result. All else being equal, the lower the NNT,
the better. “
“The relative risk (RR) tells us the risk of an outcome in
one group with the risk factor (eg increased IOP) compared
to the risk of an outcome in a group without the risk factor
(eg normal IOP). A derivation of the RR, the relative risk
reduction (RRR) tells us the proportion of the baseline risk
that can potentially be removed by treating the risk factor
in question.”
“A relative risk reduction (or relative risk ) of 50% could
mean an ‘absolute’ reduction from 100% to 50% or from 1% to
0.5%. These figures translate into an NNT of 2 for the first
example, versus 200 for the second.” All else being equal,
we would probably always use the therapy that provides an NNT
of 2 and very rarely use one with an NNT of 200.”
“However, results from some recent studies have been presented
in an isolated manner that might encourage very aggressive
lowering of the IOP with possibly detrimental effects. Both
OHTS and the EMGT state that each mmHg-lowering of IOP is
associated with a 10% lowering of risk. First, we must
remember that in both these studies, this conclusion was
the result of ‘post hoc’ analyses; such analyses are always
interpreted with care. “
M & T Commentary:
We have all heard that decreasing IOP in the OHTS resulted
in a relative risk reduction of about 50%, but, the absolute
risk reduction was only about 5% (from roughly 10% to 5%
conversion from ocular hypertension to glaucoma.) It is
always important to have at least a basic understanding of
biostatistics to meaningfully understand study results.
Dr. Ravi Thomas nicely gives us a perspective of some of
these data concepts.
From: What Does the Sclera Have to Do With
Glaucoma?
by C. Ross Ethier, et. al.
“the biomechanics of the corneo-scleral shell
affect the optic nerve head quite profoundly. Why? It
has to do with the effective stiffness: the thick, solid sclera
is much stiffer than both neural tissue and the porous lamina
cribrosa. It’s as if a wire rope (the sclera) were attached
to a thick elastic band (the lamina cribrosa); if you pull
on the wire rope, the elastic simply has to follow. The implication
is that acute deformities of the lamina cribrosa and neural
tissue depend critically on how much the sclera deforms, and
hence on the mechanical properties of the sclera.”
“we wonder whether this might explain some of the association
between central cornea thickness and progression seen in the
OHTS study, even after correction of corneal thickness-compensated
IOP.”
From: Special Editorial on Risk Management
by E. L. Greve, et. al.
- Weinreb et. al
“the risk of developing unilateral blindness from ocular
hypertension over 15 years ranges from 1.5% to 10.5% untreated,
and from 0.3% to 2.4% treated.”
“Based on cross-sectional data from the Baltimore Eye
Survey (non-institutionalized persons with glaucoma), Quigley et.
al. estimated that in the US , an average person who developed
initial glaucomatous field loss at age 60 would probably
not become legally blind in either eye within his or her
lifetime. Thus, only a small proportion of those with glaucoma
progress to bilateral blindness in their lifetimes. “
“In a life-table modeling, the average time from first visual
field loss to death was estimated to be 13 years for whites
and 16 years for blacks.
“In another estimate on a cross-sectional clinic data set, Jay
and Murdoch reported that with optimum treatment the
interval between early glaucomatous field loss and end-stage
glaucoma was 38 years. Using worse eye data, with untreated
IOPs in POAG between 21-25mmHg, the average time for untreated
glaucoma to progress to near blindness after early field
defect was 14 years, and with pressures of 26-30mmHg 7 years.”
“In a prospective follow-up study of ten years, Rasker et.
al. reported that visual field defects developed in 6% of
125 OHT patients. The mean time to first VF defect was 7±3.4
years. From POAG data, they estimated that eyes with treated
early glaucoma with progression, end-stage glaucoma may
be reached in about 33 years.”
“The question whether it is acceptable to wait for the
appearance of visual field defects remains unanswered.
The goal of glaucoma treatment is to preserve the patient’s
Quality of Life. One of the clearest factors for development
of future blindness is the presence of advanced visual field
defects. Such a risk of blindness has not been reported
for the presence of early damage. Once early damage has
been established and vigorous treatment is installed, recent
studies have shown that progress is slow.”
M & T Commentary:
It is evident for most patients that glaucoma is a very slowly
progressive disease. Rarely is there ever a need to make
hasty decisions regarding glaucoma care.
- Friedman et. al. : Comments about risk factors
“What is a risk factor: the presence of a risk factor indicates
that the patient has a higher probability of developing
a disease than a population with same age and without the
risk factor, e.g. high IOP. WHAT IS NOT A RISK FACTOR:
EARLY DISEASE IS NOT A RISK FACTOR, NOR IS SUSPICION OF
EARLY DISEASE.
“Suspicion means that there may or may not be early disease.
Suspicion is a reason for paying extra attention to the suspect,
including careful evaluation of all aspects of the examination,
careful baseline documentation and frequent follow-up visits
in order to detect possible progression.
In the paper by Friedman, et. al., visual field suspicion
and disk suspicion are ranked under risk factors. These
factors surely are different from IOP which is a risk factor
in the true sense of the definition. It seems prudent not
to rank a suspicious visual field or disk under risk factors. If
we remove suspicious findings from the risk factors, we will
find somewhat to our surprise that ONLY a higher IOP, a thinner
cornea and older age remain. Assuming that older age
is balanced by shorter life expectancy and knowing that the
evidence for thinner cornea as an IOP independent risk factor
is lacking, WE MAY CONCLUDE FROM THIS PAPER THAT IOP IS THE
ONLY RISK FACTOR. Weinreb et. al. write: ‘Unfortunately current
available data are insufficient to accurately estimate levels
of risk in most glaucoma patients.’”
“What does this mean for management of the glaucoma suspect?
M & T: this is really good information...
1. The risk of developing unilateral blindness is relatively
low, meaning that only selected high risk ocular hypertension
patients should be treated.
2. Apart from the risk factor ‘higher IOP’ (corrected
for CCT) only field or disk suspicion factors may help up in
making a treatment decision (and additionally the presence
of pseudoexfoliation).
3. The follow-up of suspicion factors allows us to let
suspicion turn into the certainty of established damage (and
changing the diagnosis from suspect to glaucoma) only after
progression has been identified (i.e. significant change surpassing
long-term variability).
4. If the Rate of Progression is such that reduction of
Quality of Life is expected to occur in the patients lifetime,
treatment is justified.
NOTE: Although this is the ideal situation, measurement of
Rate of Progression may not be possible. In that case the second
best is to confirm progression (e.g. by a series of visual
field examinations or by additional disk data).”
M & T Commentary:
It may very well be that the “glaucoma scanning devices” will
have their clinical forte in helping us assess progression.
We postulate they are better than visual fields at this task,
especially in early disease. Visual fields are probably better
at following progression once a visual field defect is established
(i.e., reliable and consistent upon repeated testing.)
“In practical terms:
- In the presence of a CCT corrected IOP repeatedly at or
over 30mmHg: treat.
- In the presence of a CCT corrected IOP repeatedly between
22 and 30mmHg: follow at regular intervals.
- In the presence of a CCT corrected IOP between 22-30mmHg
and in addition a suspicious field or disc factor, follow
at more frequent intervals in order to establish (rate of)
progression .”
“ ’Because of large interpretation variability of progression
it may be reasonable to leave some (low risk) patients
untreated and establish a rate of progression first.’ This
was written for patients with established glaucoma. It is
all the more applicable to ocular hypertension .”
“What is the main and most practical reason for early
detection of glaucomatous damage: not necessarily the
installment of early treatment, BUT the availability of a
means of establishing progression and preferably rate (velocity)
of progression. This will by itself allow for earlier treatment
which is now based on the demonstration of progressive disease.
M & T Commentary:
Notice how experts carefully and systematically assess the
patient before treatment. There is rarely ever a need to
rush therapeutic intervention.
“In practice, the above approach should be considered for
implementation where the infrastructure is available to provide
careful follow-up, where the patient is committed to attend
regularly and when the variability in the results obtained
is small enough to enable identification of progression in
a clinically relevant time period. In the absence of appropriate
follow-up, consideration should be given to treating those
with the risk factor elevated IOP.
“More than 3000 Japanese over 40 years participated (78% participation)
in this cross-sectional epidemiology studyx The prevalence
of POAG was 3.9% of which more that 90% were of the NPG type.
The mean CCT was 518mm and not significantly different from
non-glaucoma eyes (520mm)
“The non-significance of CCT as a risk factor for glaucoma
in this population was confirmedx Of the POAG patients,
93.9% were undiagnosed.”
M & T Commentary:
It appears that “failure to diagnosis” glaucoma is not just
an American phenomenon.
On Examination Methods - IOP and CCT
Comment by Clive Migdal
“The response to topical medication varies widely amongst individuals,
with many factors being responsible for this variability.”
“Thinner corneas had a lower measured IOP after four to
six weeks of therapy with either beta-blockers or prostaglandins.
CCT measurements were not correlated with any of the other
parameters investigated. Three possible mechanisms can be
postulated by which CCT might influence the measured IOP
response to ocular hypertension medications, namely differential
pharmacokinetics, lower baseline IOP and differential corneal
compliance, with a combination of the latter two hypotheses
being most likely.”
“Ultimately, the focus of glaucoma management must still be
on the optic nerve and visual field. In clinical practice,
however, CCT measurements can help the clinician better interpret
a patient’s response to therapy.”
Comment by James Brandt
“The authors report that those treated with PGAs have, on
average, thinner corneas than their untreated counterparts
or those treated with other medications. The authors hypothesize
that, since the mechanism of PGAs is to modify and partially
digest the extracellular matrix of the ciliary muscle, perhaps
a similar effect is occurring in the cornea, with a drug-related
thinning.”
“Since clinicians tend to use the most powerful medications
in patients presenting with more advanced disease, a study
of this design and size is subject to a selection bias wherein
patients treated with PGAs might have thinner corneas on a
basis unrelated to drug effect. These criticisms aside, I
do believe that the authors are probably correct in suggesting
that PGAs likely alter the mechanical properties of the cornea,
including CCT and their study provides the first tantalizing
data to support this.”
On Structure:
Comment by Harry Quiqley:
1) Strain on the lamina is sufficient to damage nerve fibers
directly; 2) the sclera is more important than the lamina itself
in determining what the lamina will do; 3) the surface of the
disc does different things from the lamina; 4) the central
retinal artery, the pia, and the cerebrospinal fluid pressure
are pretty meaningless to the strain.”
On Function and Structure:
Comment by Balwantray Chauhan:
“While modern imaging devices such as scanning laser tomography,
optical coherence tomography and scanning laser polarimetry
have been in clinical practice for over a decade, longitudinal
data from these devices is scantx Mohammandi and colleagues
determined whether baseline status with GDx Nerve Fibre Analyzer
was predictive of glaucomatous field loss They found that
subjects with thinner baseline nerve fibre thickness were at
a higher risk of visual field conversion.”
“the conversion rate of subjects with thinner nerve fibre
layer parameters after four years of follow-up was five to
seven times higher than the conversion rate of even the untreated
subjects in the Ocular Hypertension Treatment Trial.” M & T:
So it would seem that a thin (or thinner than average) retinal
nerve fiber layer is a risk factor for glaucomatous progression.
Baseline NFL measurement would be a wise parameter to have
for future comparison.
“The authors were careful to conduct a multivariate analysis
that took into account the baseline differences in the optic
disc and visual field and still found the baseline GDx parameters
to be associated with conversion.”
On Risk Factors:
Comment by Tetsuya Yamamoto
“It is well known that optic disc hemorrhages are frequently
observed in glaucoma cases. They are more frequently seen
in cases with lower intraocular pressure (IOP), i.e., a normal-tension
glaucoma. Thus, they are suggestive of the existence of IOP-unrelated
pathogenic factors of glaucomatous optic neuropathy. More
importantly from a clinical standpoint of view, many glaucoma
clinicians believe they are indicators of glaucoma progression.”
“One [factor] is that disc hemorrhages more likely develop
at relatively lower IOP during follow-up. The results
are in good agreement with our experience that disc hemorrhages
are observed more commonly in the presence of relatively
lower IOP.”
On Medical Therapy: Persistency
Comment by Gail Schwartz
“This clinical outcome study by Zhou et. al. evaluates persistency
(time on therapy) in patients with primary open-angle glaucoma
naïve to therapy in the United Kingdom . Six classes of IOP-lowering
agents were analyzed. The database selected was a large UK
resource previously established as valid for clinical research,
with 2,001 patients meeting selection criteria. From both
a patient care and resource management standpoint, the clinician
seeks to begin a therapy upon which the patient would remain
for the foreseeable future. This entails a combination of
efficacy with drug tolerability and patient adherence to therapy. The
results supporting greater persistency with latanoprost relative
to the other agents in this study, is very much in accordance
with the published literature, both United States and European,
as noted by the authors.”
“As newer prostaglandin agents have entered the market, their
inclusion in a future database analysis would also add to the
literature.
“Persistency , offering a broader picture than compliance
alone, is becoming an increasingly important tool in patient
management. Regardless of the quality of the clinical decision
making, persistency is required for long term prevention of
glaucomatous progression.”
On Medical Therapy: Additivity of Prostaglandins
Comment by Carl Camras
“These findings lead the authors to conclude that adding either
of the newer prostaglandin (PG) analogs, travoprost (TP; Travatan)
or bimatoprost (BP; Lumigan) to the regimen of patients receiving
latanoprost (LP; Xalatan) might result in greater ocular hypotensive
efficacy. However, these implications must be tempered considerably
for many reasons. A very important weakness of the study design
was the failure to mask. The study was performed in monkeys.
Any illusion to the clinical applicability of the findings
in humans represents an extrapolation with questionable validity.”
“In conclusion, monkeys simply are not humans. The findings
in the present study of monkeys are not consistent with published
studies in humans, which fail to demonstrate additivity of
the three major PG analogs.”
M & T Commentary:
At this point in time, if a prostaglandin works well at reducing
IOP, we see no reason to try adding another prostaglandin.
It is known, but unexplained, that b.i.d. dosing of latanoprost
did not perform s well as once daily dosing.
STUDIES
Prevalence of primary open-angle glaucoma in a Spanish population:
the Segovia study
CONCLUSION: The prevalence of POAG in this Segovia
population is 2.1%, similar to that estimated in previous studies
performed predominantly in Caucasian populations.
The prevalence of primary open-angle glaucoma in Japanese:
the Tajimi Study
CONCLUSIONS: The prevalence of POAG in this population
was 3.9%. In 92% patients with POAG, the IOP was 21mmHg
or less.
Is glaucoma associated with motor vehicle collision involvement
and driving avoidance?
CONCLUSIONS: Older persons with glaucoma drive at
least as safely as, if not more safely than, older persons
without glaucoma.
Impact of diabetes on glaucoma screening using frequency-doubling
perimetry
PURPOSE: To determine whether diabetes is a potential
source of abnormal test results in glaucoma screening by
use of frequency-doubling perimetry.
CONCLUSIONS: Frequency-doubling perimetry is abnormal
in some patients with diabetes, including some patients with
diabetes without clinical evidence of diabetic retinopathy.
Abnormal FDT testing in diabetic eyes may not represent glaucomatous
visual field loss. Diabetes may be a source of ‘false-positive’
test results when this technology is used for glaucoma screening.
M & T Commentary:
Caution, and repeat VF testing using standard perimetric technology
is in order for diabetic patients who demonstrate questionable
results on FDT testing.
Central corneal thickness and measured IOP response to
topical ocular hypotensive medication in the Ocular Hypertension
Treatment Study
PURPOSE: to determine whether central corneal thickness
(CCT) correlates with measured intraocular pressure (IOP)
responses to topical hypotensive medication in the Ocular
Hypertension Treatment Study (OHTS).
CONCLUSIONS: individuals with thicker corneas had
smaller measured IOP response to ocular hypotensive medication
than those with normal or thin corneas.
Corneal thicknesses in children
CONCLUSIONS: Pediatric central and paracentral corneal
thicknesses increase slowly over time and reach adult thicknesses
at 5 to 9 years of age.
Impact of prostaglandin-F2a - analogues and carbonic
anhydrase inhibitors on central corneal thickness -- a cross-sectional
study on 403 eyes
CONCLUSIONS: The present findings suggest that the
topical application of prostaglandin F2a analogues onto
the cornea reduces the central corneal thickness significantly.
These changes might be attributed to the effects of PGF2a
analogues on the extracellular matrix of the corneal stroma
via upregulation of matrix metalloproteinases. In clinical
practice, corneal thinning under local PGF2a analogue treatment
could result in underestimation of intraocular pressure levels
as measured by applanation tonometry.
M & T Commentary:
Interesting, but further research will need to be done to see
if there is clinical relativity to these changes.
Central corneal thickness of Caucasians, Chinese, Hispanics,
Filipinos, African Americans, and Japanese in a glaucoma
clinic
CONCLUSIONS: Studies examining individual Asian subpopulations
in isolation suggest that differences in CCT may exist among
different Asian groups. The results of this study indicate
that CCT does, in fact, vary among Asian subpopulations;
Japanese have thinner corneas than Chinese and Filipinos.
Caucasians, Chinese, Hispanics, and Filipinos have comparable
CCT measurements, whereas the corneas of African Americans
are significantly thinner. Additionally, older individuals;
glaucoma suspects; and participants with NTG, POAG, PEX,
and CACG have thinner corneas.
Visibility of lamina cribrosa pores and open-angle glaucoma
CONCLUSION: Lamina cribrosa pores are commonly
visible in glaucoma suspects and less commonly visible
in normals. This association, however, is almost entirely
because of an increased visibility associated with larger
vertical cup-disk ratio and optic disk size.
Comparison of the Tono-Pen and Goldmann tonometer for measuring
intraocular pressure in patients with glaucoma
Combining the analysis for both groups, the Tono-Pen significantly
underestimated the IOP when the pressure was > 20mmHg.
CONCLUSIONS: The Tono-Pen cannot replace the Goldmann
tonometer in the sense that it will give the same readings
of IOP. The accuracy of the Tono-Pen increased, if at least
two measurements are taken per eye and then averaged.
Comparison of dynamic contour tonometry with Goldmann applanation
tonometry
CONCLUSIONS: IOP measurements by DCT are highly concordant
with IOP readings obtained from GAT, but do vary in CCT and
have a lower intra- and interobserver variability. DCT seems
to be an appropriate method of tonometry for routine clinical
use.
Pressure phosphene self-tonometry: a comparison with Goldmann
tonometry in glaucoma patients
CONCLUSIONS: With proper training and technique, self-tonometry
with the PPT appears to be accurate up to at least 25mmHg
and is reproducible. The PPT was sensitive and specific
in detecting elevated IOP of more than 21mmHg. As patients
were expected to seek ophthalmic care before self-measured
IOP reaches 25mmHg, the PPT may have a value for self-monitoring.
Patients rated the PPT as satisfactory for home use. Because
the PPT is portable and relatively inexpensive and requires
no topical anesthesia or direct contact with the eyeball,
it may have potential as an instrument for home self-tonometry.
M & T Commentary:
While it is nice to know this unit is reasonably accurate,
its forte is not in absolute IOP measurement, but in detecting
the magnitude of diurnal IOP curves. It can be very helpful
for this purpose, and is available from Bausch & Lomb.
Goldmann tonometry after hyperopic laser in situ keratomileusis:
Comparison between retreated and nonretreated patients
PURPOSE: To identify differences in applanation tonometry
between retreated and nonretreated eyes (primary LASIK eyes)
6 months after hyperopic laser in situ keratomileusis.
CONCLUSIONS: After hyperopic laser in situ keratomileusis
there was no significant difference in Goldmann applanation
tonometry between retreated and primary LASIK eyes.
Impact factors on intraocular pressure measurements in
healthy subjects
AIM: To evaluate whether intraocular pressure (IOP)
calculation by applanation tonometry is determined more essentially
by the subject’s neck position or by neck constriction.
IOP was measured by applanation tonometry with the TonoPen
on sitting participants under four different conditions:
with open collar upright (A) or with the head in the headrest
of a slit lamp (B), with a tight necktie upright (C) or in
a slit lamp position (D). All measurements with neck constriction
were performed 3 minutes after placing the necktie.
CONCLUSION: Applanation tonometry may be inaccurate
if performed in slit lamp position. In contrast, tight neckties
do not significantly affect IOP evaluation in healthy subjects.
M & T Commentary:
This differs from the article recently in the “British Journal
of Ophthalmology” showing that a tight necktie could cause
an increase in IOP. Nonetheless, slit lamp-mounted applanation
tonometry is potentially problematic in obese patients, those
with large breasts, blepharospastic patients, and those who
simply have difficulty positioning themselves correctly and
comfortably into the slit lamp. For this sizable subpopulation,
we readily default to a hand-held (Perkins or Kowa) applanation
tonometer. It is state-of-the-art Goldmann tonometry, but
with a hand-held rendition which greatly facilitates the
acquisition of accurate tonometry. We strongly recommend
that all practices have one of these units.
Short-wavelength automated perimetry results are correlated
with optical coherence tomography retinal nerve fiber layer
thickness measurements in glaucomatous eyes
CONCLUSION: Retinal nerve fiber layer thickness measured
with OCT is topographically correlated with glaucoma VF defects
measured with SWAP.
Intraobserver reproducibility of retinal nerve fiber layer
measurements using scanning laser polarimetry and optical
coherence-tomography in normal and hypertensive subjects
CONCLUSIONS: Retinal mapping software of both nerve
fiber analyzers allows reproducible measurement of RNFL in
both healthy and ocular hypertensive eyes, and shows fair
correlations and good intraobserver reproducibility. However,
in our study, GDx showed a better test-retest correlation.
M & T Commentary:
We love the GDx-VCC and highly recommend it!
Retinal nerve fiber layer thickness measurements with scanning
laser polarimetry predict glaucomatous visual field loss
PURPOSE: To assess whether baseline retinal nerve
fiber layer (RNFL) measurements obtained with a scanning
laser polarimetry, the GDx Nerve Fiber Analyzer, are predictive
of development of repeatable glaucomatous visual field damage
in glaucoma suspect eyes.
CONCLUSIONS: Thinner baseline SLP RNFL measurements
were independent predictors of visual field damage. In addition
to thinner SLP RNFL measurements, higher baseline SAP PSD,
and baseline glaucomatous stereophotograph assessment each
contributed to an increase risk in the development of abnormal
visual fields in glaucoma suspect patients. SLP RNFL measurements
were independently predictive of future visual loss even when
age, IOP, CCT, vertical cup disk ratio, and SAP PSD were included
in the model.
Sensitivity and specificity of scanning laser polarimetry
using the GDx
CONCLUSIONS: Detection of (early) glaucoma damage
by the GDx, evaluated by trained experts, can be extremely
high. To optimize its benefit in clinical routine, training
in interpreting GDx printouts is highly recommended. Detection
of localized NFBD is crucial, even for experts.
Diagnostic accuracy of the GDx VCC for glaucoma
CONCLUSIONS: The GDx VCC allowed easy, rapid, and
accurate discrimination between healthy and glaucomatous
eyes. The NFI was the best discriminating parameter. The
GDx VCC seems to fulfill criteria for a glaucoma screening
device.
Comparison of retinal nerve fiber layer thicknesses measured
by optical coherence tomography and scanning laser polarimetry
(GDx)
CONCLUSIONS: The RNFL thickness obtained using OCT
is generally greater that that using GDx. Furthermore, a
better correlation between visual function and RNFL thickness
was obtained for OCT compared with GDx.
M & T Commentary:
Bottom line - either of these devices can provide valuable
information to the glaucoma diagnostic evaluation.
Factors associated with optic disc hemorrhages in glaucoma
CONCLUSIONS: Optic disc hemorrhages were associated
with diabetes and aspirin use and were observed at relatively
lower IOP during follow-up.
Optic disc hemorrhages detected in a large-scale eye disease
screening project
CONCLUSION: Disc hemorrhages occur more frequently
in females, in elderly persons, and in glaucoma cases in
Japanese aged 40 or older. The intraocular pressure of the
eyes with the disc hemorrhages is close to that of the normal
population.
Corticosteroids are the main culprits in drug-induced glaucoma
Approximately 18-36% of the general population and 46-92% of
patients with primary open-angle glaucoma experience an increase
in intraocular pressure (IOP) after topical ocular administration
of corticosteroids for 2-4 weeks.
M & T Commentary:
So, isn’t it nice that most all inflammatory eye conditions
resolve in less than two weeks?
Efficacy and safety of the latanoprost/timolol maleate
fixed combination vs concomitant brimonidine and latanoprost
therapy
AIMS: To evaluate the efficacy and safety of latanoprost/timolol
maleate fixed combination (LTFC) given once daily vs the
concomitant therapy of brimonidine twice daily and latanoprost
once daily in primary open-angle glaucoma or ocular hypertensive
subjects.
CONCLUSION: This study suggests that LTFC and concomitant
therapy of brimonidine and latanoprost provide statistically
similar diurnal reduction from an untreated baseline.
Comparison of once-daily nonpreserved timolol and timolol
maleate gel-forming solution associated with latanoprost
CONCLUSION: This short-term study has demonstrated
the equivalence of nonpreserved timolol to timolol maleate
gel-forming solution in terms of IOP control.
M & T Commentary:
This was demonstrated to be true a few years ago. There is
no reason to prescribe more expensive gel solutions when
less expensive, conventional solutions perform just as well.
A persistency and economic analysis of latanoprost, bimatoprost,
or beta-blockers in patients with open-angle glaucoma or
ocular hypertension
CONCLUSIONS: Patients were more persistent with latanoprost
and demonstrated lower intraocular pressures, fewer visits,
and fewer medicine changes when compared to bimatoprost or
beta-blocker therapy. In contrast, the beta-blocker group
provided lower overall cost.
Intraocular pressure, safety and quality of life in glaucoma
patients switching to latanoprost from adjunctive and monotherapy
treatments
PURPOSE: To evaluate efficacy, safety and quality
of life in ocular hypertensive or open-angle glaucoma patients
changed to latanoprost from previous therapy.
CONCLUSIONS: In a clinical setting, patients who have
their mono- and adjunctive therapy treatment substituted for
latanoprost may on average experience reduced IOP, decreased
side effects and increased quality of life measures.
The efficacy and safety of once-daily versus once-weekly
latanoprost treatment for increased intraocular pressure
We [S. Kurtz, G. Shemesh] evaluated the efficacy and safety
of latanoprost eye drops once-weekly, compared to once-daily
for improving patient compliance. The difference between post-treatment
IOP was insignificant in both groups at each time point. The
study group had fewer minor side effects than the control group
(1/10 versus 6/10, respectively). Latanoprost treatment once-weekly
was as effective, and bore fewer minor side effects, as once-daily
treatment after 3 months of follow-up.
Optic nerve and neuroprotection strategies
CONCLUSIONS: A battery of agents now exist that can
blunt animal ganglion cell death irrespective of whether
the insult was to ganglion cell body or the myelinated axon.
Whether this information can be applied for use in patients
remains a matter of debate, and major obstacles need to be
overcome before laboratory studies may be applied clinically.
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