Excerpts
From: The International Glaucoma Review, Volume 8-4,
2007
(Eighth in a Series)
The “International Glaucoma Review: The Journal of the Association
of International Glaucoma Societies” (www.glaucom.com) is published
every four months. The Optometric Glaucoma Society, of which
we are founding members, is a component member of the sixteen
societies which composes this worldwide network of glaucoma
specialists. This expert publication reviews the world glaucoma
literature from the previous four months and provides abstracts
and reviews of the most salient information from that time
period in a single publication. We are pleased to provide
for you, our colleagues in optometry, the following selected
quotes (or in-context paraphrases), and our commentaries, from
the Volume 8-4, 2007 issue. We hope you will find great benefit
as we take you deeper and deeper into the subspecialty of glaucoma.
- Randall K. Thomas, O.D., M.P.H.
- Ron Melton, O.D., F.A.A.O.
Uveal Effusion and Primary Angle Closure Disease
Relative pupillary block is considered the most important trigger
of the angle closure mechanism in primary angle closure (PAC).
However, the pupillary block mechanism is not a really ‘primary’
mechanism. Relatively short axial length, usually related
with hyperopia is a well known anatomical background of PAC.
Hyperopia and those with a short axial eye have shallow anterior
chamber by nature. PAC is age dependent. Increased lens thickness
due to the lens epithelial growth may account for part of
the mechanisms of anterior chamber shallowing and increased
chance of relative pupillary block mechanism with age. Additionally,
subclinical uveal effusion has been observed by ultrasound
biomicroscope (UBM) in various phases of PAC eyes.
M & T Commentary
Just for perspective, “supraclinical” uveal effusion associated
with Topamax use is thought to be the mechanism resulting
in acute, bilateral, simultaneous angle closure.
News from Glaucoma Meetings
From the Optometric Glaucoma Society Annual Meeting:
- Patient adherence to prescribed drug therapies is better with
prostaglandins followed by beta blockers, topical CAIs and
alpha agonists. Managed care data have shown that approximately
50% of newly diagnosed POAG patients did not return for follow-up
in the first 15 months, and that there was a relationship between
therapeutic persistence and failure to return for follow-up.
- Assessment of patient adherence to therapy depends strongly
upon interviewer technique, Open-ended questions, such as:
“Tell me how you have been taking your medication,” often are
useful.
- Structural and functional measurements may be used to provide
confirmation of each other. Measurements in humans and monkeys
demonstrated that, in cases of disagreement, standard automated
perimetry generally indicated greater loss of retinal ganglion
cells (RGCs) than was seen in the retinal nerve fiber layer
(RNFL), suggesting that measured functional losses frequently
precede measured structural changes.
From the Annual Basel Glaucoma Meeting:
- Non-IOP lowering treatments also include nutritional sources
of antioxidants: red wine, dark chocolate, green or black tea
and coffee are all polyphenolic substances with free radical
scavenging activity; coffee additionally contains the compound
3-methyl-1,2-cyclopentanedione (MCP), which has been shown
to be a selective scavenger of the peroxynitrite; bilberry
is rich in anthocyanosides, which has strong scavenging properties.
M & T Commentary
What this means to any individual (or group) is not known,
but it is generally interesting information.
Baseline Predictions
Computerized imaging of the optic nerve and peripapillary retinal
nerve fiber layer provide unique and clinically relevant
information regarding glaucoma risk assessment and prediction
of subsequent progression. Using the laser polarimetry (GDx-VCC),
Mohammadi and colleagues demonstrated that thinner baseline
retinal nerve fiber layer (RNFL) measurements were independently
predictive of subsequent visual field loss among a population
of glaucoma suspects.
For the clinician, the single most important question is how
to assess the risk of glaucoma in an individual patient. While
single measures are useful for assessing risk, consideration
of ALL clinical information will provide the most robust strategy
for identifying patients in whom treatment is beneficial.
Clinical Glaucoma
Taverez et al. sought to examine the variability of published
definitions for ocular hypertension and evaluate the influence
of the OHTS on the published literature. In short, they found
the definitions were highly variable and the influence of
the OHTS was small. Central corneal thickness (CCT) was reported
in 13.1% of articles and appears uninfluenced by the OHTS
publications in 2001 and 2002 suggesting the importance of
CCT measurements.
M & T Commentary
This is astonishing, since the body of glaucoma experts has
found CCT assessment to be one of the most important revelations
from the OHTS.
OHT and Risk
Risk and risk calculation bathe in the light of attention now
that risk calculators (RC) have become widely available.
Do risk calculators have an advantage over the ophthalmologists’
common sense? Mansberger and Cioffi asked 52 ophthalmologists
to estimate the risk of developing glaucoma in five years
in 4 factitious OHT patients. The ophthalmologists were aware
of the results of the OHTS. The ophthalmologists’ results
were compared to those of a risk calculator. The authors
concluded that: 1. There is wide variety among the risk estimation
of ophthalmologists; 2. There is a substantial difference
between the ophthalmologists’ estimate and the calculated
risk. This is a neat, clever and important little study.
It shows that if we all use the same risk calculator at least
we will manage our patients based on the same risk estimate.
The vital question remains: which calculator estimates the
real risk. The answer will come.
M & T Commentary
We think that no device, program, algorithm, or concept can
replace an attentive, well-trained, compassionate optometrist
or ophthalmologist.
Optic Disc Hemorrhage (ODH)
In this large and very interesting study, Budenz et al. analyzed
optic disc hemorrhages (ODHs) in 1618 OHTS patients. They
found ODHs in a total of 123 or 7.6% of studied patients.
Only 16% of ODH patients had been diagnosed clinically and
the other 84% were detected only after inspection of disc
photographs. Risk indicators for ODH were much the same as
risk indicators for development of glaucoma damage in the
OHTS, i.e., older age, thinner corneas, and a positive family
history. Not surprisingly, the ‘glaucoma markers’ higher
pattern standard deviation (PSD) and higher C/D ratios were
also significantly associated with ODH. It is interesting
to note that higher IOP was not associated with ODHs despite
the great importance of IOP for development of glaucoma damage.
The risk for development of glaucoma was 6 times larger in
ODH eyes than in eyes where no ODHs had been photographed.
The risk in ODH eyes was 3.7 even in a multivariate analysis,
which shows the importance of really looking for ODH in patients
with ocular hypertension and other glaucoma suspects.
It has often been said that an ODH is a sudden catastrophic
event, which is often soon followed by the development of a
notch and visual field deterioration. This is not true; even
when repeated hemorrhages have been seen the disc and field
can remain unchanged. The present study from the large OHTS
material really demonstrates this very clearly; 87% of ODH
eyes had still not developed a POAG end point at the end of
the observation period.
The author remarks, “Reflecting on the fact that only 16%
of patients were detected on clinical examination (even with
leading glaucomatologists participating in OHTS!), I cannot
help thinking back on my days as a young scientist 25 years
ago, when it was common to hear leading glaucoma researchers
stating that ODHs were very rare or non-existing in their countries.
Given how easy it is to miss ODHs, it is not difficult to understand
why it took such a very long time before ODHs were universally
accepted as common signs of glaucoma. We don’t see what we
look at, but what we look for.
“We must be humble and realize that the finding of an optic
disc hemorrhage in a glaucoma suspect has clear clinical significance,
but that not finding one does not mean much, because: either
an ODH can have been overlooked on clinical examination; or,
give their intermittent nature, ODHs can be present only between
examinations.”
Diabetes Mellitus
De Voogd et al. report that diabetes at baseline was not associated
with the development of primary open angle glaucoma (OAG)
in a population-based study conducted in the Netherlands.
The authors conclude that diabetes at baseline is not associated
with incident POAG, but in fact, in the adjusted analysis
the authors reported a 35% lower likelihood of POAG in persons
with diabetes at baseline. The findings of this study are
therefore consistent with no difference in incidence rates
between those with diabetes and those without, but the study
was underpowered to answer the question of risk.
M & T Commentary
If diabetes and glaucoma are associated, then the association
must indeed be very weak since no one seems to be able to
claim or disclaim this speculation with authority. The pendulum
appears to be swinging toward no clinically significant association,
which is in sharp contrast to the dogma of the latter part
of the 20th century, when belief in a positive association
was widespread.
NTG – IOP
Fluctuation in intraocular pressure (IOP) is an important issue
in the diagnosis and treatment of glaucoma. A significant
percentage of normal-tension glaucoma patients have their
IOP peaks outside of office hours.
Reports From Recent Studies
Use of gonioscopy in Medicare beneficiaries before glaucoma
surgery. Results: Overall, gonioscopy is apparently performed
in 49% of Medicare beneficiaries during the 4 to 5 years
preceding glaucoma surgery. This rate was significantly lower
in patients with OAG (46%), as compared with anatomic narrow
angle (58%) and ACG (57%) patients. Conclusions: Gonioscopy
examination before glaucoma surgery in Medicare beneficiaries
is underused, and/or miscoded, given current recommendations.
Underuse is of particular concern in patients undergoing
laser iridotomy, as it is the diagnostic test of choice in
ACG.
The ISNT rule and differentiation of normal from glaucomatous
eyes. Objective: To determine whether the ISNT rule (that normal
eyes show a characteristic configuration for disc rim thickness
of inferior x superior x nasal x temporal) widely used for
clinical evaluation of the optic nerve head can differentiate
normal from glaucomatous eyes. Conclusion: The ISNT rule is
useful in differentiating normal from glaucomatous optic nerves
and is unaffected by race.
M & T Commentary
We love the ISNT rule concept, mainly because it forces doctors
to truly study the optic nerve head, thus improving patient
care.
Comparison of the Moorfields classification using confocal
scanning laser ophthalmoscopy and subjective optic disc classification
in detecting glaucoma in blacks and whites. Conclusions: Subjective
optic disc grading by glaucoma specialists outperformed the
MRC with the HRT II in both black and white subjects. Both
subjective and objective diagnostic methods were associated
with similar sensitivity and specificity between racial groups.
The MRC was more likely to provide an incorrect diagnosis in
subjects with large optic discs.
The role of scanning laser polarimetry using the GDx variable
corneal compensator in the management of glaucoma suspects.
Conclusions: Scanning laser polarimetry using the GDx-VCC is
an important tool in defining the management strategies of
glaucoma suspects. In screening for glaucoma, however, GDx-VCC
results should not be used in isolation, but in conjunction
with conventional methods of optic disc and visual field assessment.
M & T Commentary
No one test is comprehensively diagnostic of glaucoma. It is
the cerebral integration of ALL diagnostic components of
the glaucoma workup that yields the most sensitive and specific
disease assessment.
Comparison of optic disc and retinal nerve fiber layer thickness
in nonglaucomatous and glaucomatous patients with high myopia.
Purpose: to assess the optic nerve head (ONH) by optical coherence
tomography (OCT), confocal scanning laser ophthalmoscopy (CSLO),
and the retinal nerve fiber layer (RNFL) by OCT and scanning
laser polarimetry (GDx) in highly myopic subjects. Conclusions:
OCT, CSLO, and GDx are not useful to discriminate nonglaucomatous
and glaucomatous subjects that have high myopia.
M & T Commentary
This is excellent knowledge that is not as well disseminated
as it should be.
The probability of glaucoma from ocular hypertension determined
by ophthalmologists in comparison to a risk calculator. Conclusions:
The ophthalmologists showed a high range of estimates for the
probability of developing glaucoma in the same ocular hypertensive
patients. This may lead to either under or over treatment of
patients. Clinicians need a more exact method to determine
the probability of glaucoma from ocular hypertension.
Acute myopia and angle closure caused by topiramate, a drug
used for prophylaxis of migraine. Acute transient migraine
with shallowing of the anterior chamber is a rare idiosyncratic
response to many systemic and topical medications, including
sulfonamides. Several such cases have been reported in the
past, but are less frequently reported in recent times. We
report a case of acute progressive myopia and bilateral angle
closure due to topiramate – a drug for epilepsy and migraine
prophylaxis.
M & T Commentary
Although topiramate (Topamax) is indicated as a seizure medicine,
it is used off-label to treat migraine headaches, weight
loss, and some eating disorders, thus it is has very widespread
use. When treating topiramate-induced angle closure, remember
to substitute a cycloplegic agent for pilocarpine; otherwise
treat as non-iatrogenic angle closure. A YAG PI is not indicated.
Stopping or decreasing the dosage of the Topamax is the ultimate
cure.
Is diabetes mellitus a risk factor for open-angle glaucoma?
The Rotterdam Study. Conclusions: In this prospective population-based
study, diabetes mellitus was not a risk factor for OAG.
Prevention of dermatologic side effects of bimatoprost 0.03%
topical therapy. Purpose: To investigate the efficacy of reducing
the drop-skin contact to prevent dermatologic side effects
of bimatoprost 0.3% topical therapy. Conclusion: The reduction
of the drop-skin contact affects the regional incidence and
the extent of dermatologic skin changes that are related to
bimatoprost 0.03% topical therapy.
M & T Commentary
If such a skin change is an issue, simply dab off any residual/excess
eyedrop from the lid tissues, or try another prostaglandin.
Clinical course of bimatoprost-induced skin changes in Caucasians.
Conclusions: Bimatoprost use is associated with periocular
skin hyperpigmentation in Caucasians with variable time onset.
The periocular hyperpigmentation appears gradually, but in
this series was completely reversible with discontinuation
of bimatoprost.
Improved systemic safety and risk-benefit ratio of topical
0.1% timolol hydrogel compared with 0.5% timolol aqueous solution
in the treatment of glaucoma. Results: There was no significant
difference in the IOP-reducing efficacy between these compounds.
Conclusions: Drug-induced changes in the peak of heart rate,
and head-up tilt test results as well as plasma concentrations
of timolol, were significantly more pronounced after treatment
with 0.5% aqueous timolol than with 0.1% timolol hydrogel.
Because of the statistically similar IOP-reducing efficacy
of these formulations the risk-benefit ratio was significantly
improved when patients used 0.1% timolol hydrogel instead of
0.5% aqueous timolol.
M & T Commentary
This partially explains why we most always use 0.25% solutions
of timolol, and do so only once daily. As it has been postulated
that 0.1% may be the peak of the dose response curve, even
0.25% may be “over the top.” Certainly, the use of 0.5% timolol
b.i.d. is not in keeping with contemporary science. It is
also established that standard timolol solutions perform
as well as “gel-forming” solutions (which are more expensive).
This is why we never prescribe these gel-forming formulations.
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