Excerpts
From: The International Glaucoma Review, Volume 8-3,
2006
(Seventh 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 8-3, 2006 issue, which covers the published articles
from four months of 2006. 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.
News from Glaucoma Society Meetings Around the World
- The potentially inappropriate practice of co-prescribing topical
and systemic beta-blockers showed that approximately 20,000
concessional patients per annum are affected. Healthcare stakeholders
must alert professionals and patients of the reduced hypotensive
efficacy and increased potential for systemic side effects
from this practice.
M & T Commentary
Such a “caution” may be of importance to very few patients.
If this practice occurs about 20,000 times each year, and
if there were any consistent problem with this prescribing
behavior, surely such knowledge would be widely disseminated.
- Independent mechanism may underlie peripapillary atrophy and
disc changes in glaucoma patients; a recent study failed to
demonstrate a relationship between peripapillary atrophy and
extent of change or rate of disease.
M & T Commentary
It has long been observed that PPA and glaucoma are only loosely
associated. Thus, this finding corroborates wide-spread clinical
observations..
- The recent significant increase in the number of laser trabeculoplasties
performed in Ontario from 2002-2004 (230% increase) coincides
with the introduction of selective trabeculoplasty.
M & T Commentary
Since ALT and SLT are virtually clinically identical, the only
rational explanation for this is the need to pay for an instrument
that costs 60 to 80 thousand US dollars.
- Patients with diabetes mellitus with relatively high concentration
(HbA1c x 8%) of blood sugar had statistically significant higher
intraocular pressures (16.6 ± 2.4mmHg) than did those with
mild concentration of (HbA1c x 6.5%) of blood sugar (15.5 ±
2.5mmHg).
M & T Commentary
We doubt that such “statistical” significance translates to
“clinical” significance.
Prevalence of Glaucoma in Two Asian Countries
- The first glaucoma survey conducted in China, based on the
classification of the ISGEO (International Society of Geographical
and Epidemiological Ophthalmology), found that the prevalence
of all glaucoma was 3.8% including 2.1% of POAG and 1.5%
of PAGC. The prevalence of POAG in Japan was reported to
be 3.9%
Optic Disc and Blood Pressure
- Conflicting evidence exists with regard to the association
between blood pressure and risk of developing glaucoma. Subjects
with diastolic blood pressure (DBP) lower than 90mmHg as
a result of antihypertensive therapy had significantly thinner
neuroretinal rim measurements and larger values of cup area
compared to subjects with high DBP (x than 90mmHg) or subjects
with normal DBP levels that had not received antihypertensive
treatment. These findings are in agreement with previous
studies that have reported an association between low blood
pressure and increased prevalence and incidence of glaucoma.
A low blood pressure could be related to a low cerebrospinal
fluid (CSF) pressure, which would result in an elevated translamina
cribrosa pressure that could potentially be harmful to the
optic nerve fibers. Longitudinal studies are necessary to
more clearly define the role of blood pressure in the pathogenesis
of glaucoma.
From OHT to Glaucoma
- It is often thought that structural damage in the optic disc
precedes visual field damage in ocular hypertensive glaucoma.
Depending on the specificity of the criteria used, between
27.7% (specificity = 97%) and 53.3% (specificity = 90%) of
ocular hypertensives showed either visual field or optic
disc progression over an average of 6 years. However, there
were relatively few patients who showed both field and disc
changes. When the number of field and disc examinations were
equalized, twice as many patients had optic disc compared
to visual field changes. This evidence may suggest a higher
chance of detecting change with more examinations. As our
clinical measures of progression are only surrogates (perhaps
poor ones) of what we actually want to measure, namely structural
and functional changes at the retinal ganglion cell level,
it is not surprising that carefully performed studies such
as that of Strouthidis et al show poor correlation between
structure and function. These authors and others have sensibly
suggested the importance of both functional and structural
tests in the monitoring of glaucoma.
M & T Commentary
This explains why both an objective anatomical scan (GDx, OCT,
HRT) and subjective 24-2 visual fields are performed when
evaluating or following patients with glaucoma.
Reports From Recent Studies
Quality of life: To patients, the most important factors
regarding glaucoma and its treatment are the risks of moderate
vision loss (the ability to continue to drive) and long-term
blindness. The treatment and methods used are of much less
importance.
Measurements of optic disc size with
HRT II, STRATUSOCT™, and fundoscopy are not interchangeable: Purpose: to assess
the interchangeability of optic disc size measurement using
slit-lamp fundoscopy, optical coherence tomography (OCT-3),
and confocal scanning laser ophthalmoscopy (HRT-II) in clinical
practice. Conclusions: We observed a large range of differences
in estimating disc size with HRT, OCT, and fundoscopy. This
precludes interchangeable use of these measurements in clinical
practice, and does not allow simple conversion formulas to
be proposed. In addition, there is poor agreement between these
methods in classifying disc size as small, average, or large.
At present, estimation of both absolute and relative disc size
can only be defined separately for each measurement modality.
Intraocular pressure changes and ocular
biometry during Sirsasana (headstand posture) in yoga practitioners: Conclusion: There
was a uniform 2-fold increase in the IOP during Sirsasana,
which was maintained during the posture in all age groups irrespective
of the ocular biometry and ultrasound pachymetry. We did not
demonstrate a higher prevalence of ocular hypertensives in
this cohort of yoga practitioners nor did the risk factors
contributing to glaucoma show any correlation with magnitude
of IOP raise during the posture.
Comparison of Proview phosphene tonometer
with the Goldmann applanation tonometer in myopic eyes: Conclusions: there is
moderate agreement between the Proview phosphene tonometer
and the Goldmann applanation tonometer.
M & T Commentary
It is vital to realize that the Proview is not intended to
be Goldmann equivalent for absolute IOP measurements, but
rather to enable patients to detect relative changes in
IOP via self-testing. We are looking for wide swings in IOP,
and/or increased relative IOP outside of office hours.
Pressure phosphene self-tonometry in
a patient with Posner-Schlossman syndrome: Pressure phosphene tonometry (PPT) can be applied
with accuracy, reliability, and safety in patients with Posner-Schlossman
syndrome with potential benefits in reducing unnecessary ophthalmic
attendances by nearly 50%.
M & T Commentary
The Proview works well in this setting, where pretty hefty
changes in IOP are typical.
Comparison of the intraocular pressure
value measured with Goldmann applanation tonometer (GAT)
and non-contact tonometer (NCT): Results: The measurement results of NCT were lower
than that of GAT. Conclusion: The measurement results with
NCT are lower than that of GAT. When the IOP with the NCT is
a borderline value, it needs to be corrected with GAT in order
to discover the pathologically elevated IOP and avoid the misdiagnosis
and mistreatment of glaucoma.
The association between glaucomatous
visual field and optic nerve features in the Ocular Hypertension
Study (OHTS): Conclusions:
Both the VF and the optic disc must be monitored with equal
diligence, because either may show the first evidence of glaucomatous
damage. Changes in the ONH based on stereophotographic observation
(rim thinning, hemorrhage, or a slight increase in C/D ratio)
and VF changes (evidence of a nasal step/partial arcuate defect
or an increase in PSD) suggest that these cases have an increased
risk of developing glaucoma. Confirmation of such subtle findings
should be sought through repeat testing and correlation with
other clinical results.
Effects of sildenafil (Viagra) on the
blue-and-yellow and white-on-white Humphrey perimetry in
3 months regular use:
Conclusion: Oral sildenafil (Viagra) used regularly for 3
months produced no effect on B/Y and W/W Humphrey perimetry.
Comparison between GDx-VCC parameter
and achromatic perimetry in glaucoma patients: Conclusions: Some of the GDx-VCC indices
were significantly correlated to visual field indices in glaucomatous
patients, but NFI (Nerve Fiber Index) was the best indicator
of visual field damage.
Discrimination between glaucomatous and
nonglaucomatous eyes using quantitative imaging devices and
subjective optic nerve head assessment: Purpose: To compare the diagnostic ability
of the confocal scanning laser ophthalmoscope (HRT-II), scanning
laser polarimeter (GDx-VCC), and optical coherence tomography
(STRATUSOCT™) with subjective assessment of the optic nerve
head (ONH) stereophotographs in discriminating glaucomatous
from nonglaucomatous eyes. Conclusions: Similar diagnostic
ability was found for all imaging techniques, but none demonstrated
superiority to subjective assessment of the ONH.
M & T Commentary
This places the burden on the doctor to attentively study the
optic nerve as a matter of first importance.
Structure-function relationships using
confocal scanning laser ophthalmoscopy, optical coherence
tomography, and scanning laser polarimetry: Conclusions: These results suggest that
structure-function associations are strongest with STRATUSOCT™
measurements and are similar between HRT-II and GDx-VCC.
The effect of pupil dilation on scanning
laser polarimetry with variable corneal compensation: Conclusions: Pharmacologic
mydriasis was not found to influence the retinal nerve fiber
layer measurements acquired using the GDx-VCC, Results were
comparable to scans achieved in the same eyes prior to dilation.
Principals and clinical applications
of optical coherence tomography in glaucoma: Optical coherence tomography (OCT)
supplies morphological information from different retinal layers.
In glaucoma, analysis of the nerve fiber layer is gaining more
and more significance; losses in this layer often precede by
years functional losses in the visual field and end up in optic
nerve head changes. OCT offers a means for imaging and for
measurement of the nerve fiber layer besides morphological
analysis of ONH as one of the earliest sensitive parameters
in modern glaucoma diagnosis.
Optic disc and visual field progression
in ocular hypertensive subjects: detection rates, specificity,
and agreement: Purpose:
To examine the detection rates, specificity, and agreement
between visual field (VF) progression and Heidelberg Retina
Tomograph (HRT); rim area (RA) progression in subjects with
ocular hypertension (OHT). Conclusions: A relatively high
frequency of detected disease progression was observed with
either method, with progression by VF occurring at least as
frequently as progression by RA. Poor agreement between RA
and VF progression was observed regardless of the specificity
of the progression criteria. The results indicate that, in
patients with ocular hypertension, monitoring of both VF and
optic disc is necessary, as agreement between optic disc and
VF progression is the exception rather than the rule.
Argon laser iridoplasty in the treatment
of angle-closure glaucoma with plateau iris syndrome: Introduction: Plateau
iris predisposes to the onset of an angle-closure glaucoma
attack without pupillary block. This is a morphological anomaly
of the iris characterized by anterior inversion, root thickness
greater than the norm, and anterior rotation of the ciliary
processes into the posterior chamber, pushing the base of the
iris into the angle. Argon laser iridoplasty is useful to retract
the peripheral iris using the thermal effect of the laser to
widen the indocorneal angle. Discussion: Pure iris plateau
syndrome leading to closure of the angle is very rare compared
to pupillary block, but these two mechanisms often coexist.
The physiopathology explains that the mechanism of isolated
iris plateau is not modified by iridectomy. However, the advantage
of argon laser iridoplasty, which retracts the periphery of
the iris so as to widen the indocorneal angle, must be emphasized.
This technique can alleviate the need for high-risk filtering
surgery, but longer follow-up is necessary to evaluate its
duration and efficacy.
The course of glaucoma during pregnancy:
a retrospective case series: Conclusions: The course of glaucoma during pregnancy
is variable, and women must be monitored closely during pregnancy.
Medications may be necessary to control IOP and prevent vision
loss during pregnancy.
Treating ocular hypertension to reduce
glaucoma risk: When to treat? When to treat the patient who presents with ocular
hypertension has been a question that has ‘stumped’ the ophthalmic
community for decades. The clinician should consider key factors
such as age, thin corneal thickness measurements, large cup-to-disc
ratio and mean IOP when determining who should be treated.
However, the ultimate decision of when to treat will be determined
by other issues such as life expectancy, the general health
and the number of risk factors. Clearly, the treatment of only
high-risk patients with ocular hypertension should be considered.
M & T Commentary
This one simple paragraph embodies the essence of clinical
decision-making. “When to treat” is the ultimate decision,
and can only be made by attentively evaluating each patient
as an individual person.
Management of ocular hypertension and
chronic open-angle glaucoma by French ophthalmologists :
the role of target intraocular pressure: Discussion: The estimation of target IOP is used
by the majority of French ophthalmologists. Conclusion: This
study shows that the determination of target IOP is becoming
increasingly important in the therapeutic decision and follow-up
in the routine practice of French ophthalmologists.
Topical beta-blockers are not associated
with an increased risk of treatment for depression: Conclusions: Use of topical
beta-blockers by glaucoma patients does not appear to increase
the risk of depression in this population.
M & T Commentary
While the opposite has been taught as true for two decades,
it has been clearly shown that there is no association.
Additive effect of dorzolamide or carteolol
to latanoprost in primary open-angle glaucoma: a prospective
randomized crossover trial: Results: Mean additional IOP reduction was 0.9 ± 1.2mmHg
(5.6%) for the latanoprost-dorzolamide combination and 1.1
± 1.5mmHg (6.8%) for the latanoprost-carteolol combination.
Conclusions: Both dorzolamide and carteolol reduce IOP additively
when used in combination with latanoprost, and the additive
effect of these drugs is equal.
M & T Commentary
If all you get is an extra mmHg, is it really virtuous to complicate
the patient’s life by adding a second medication?
Effects of previous argon laser trabeculoplasty
on the ocular hypertensive action of latanoprost: Results: Latanoprost
induced a 17.5 ± 16.6% decrease in the study group (ALT-treated
eyes) and a 25.8 ± 17.2% reduction in the control eyes. Conclusions:
Latanoprost is less effective in ALT-treated eyes than in eyes
with POAG not treated with ALT.
M & T Commentary
Note the very wide-ranging responses in IOP reduction. We imaging
these findings would hold true for any of the prostaglandins.
Association between topical prostaglandin
analog use and development of choroidal neovascular membranes
in patients with concurrent glaucoma and age-related macular
degeneration: Conclusions:
No association between long-term topical prostaglandin use
and CNVM development was found in patients with AMD and POAG.
Long-term follow-up of selective laser
trabeculoplasty in primary open-angle glaucoma: Results: The success rate after
12 months determined by Kaplan-Meier survival analysis was
94%; after 24 months 85%; after 36 months 74%; after 48 months
68%; and after 72 months 59%. Conclusions: SLT is an effective
procedure offering an additional therapy option for the treatment
of POAG, but the effect diminishes over time.
M & T Commentary
This diminution of effect over time is similar to that seen
with argon laser trabeculoplasty.
Long-term outcome of selective laser
trabeculoplasty as correlated with circadian intraocular
pressure: Results: At the final
observation, IOP decreased by 2.8 ± 3.3mmHg. Success rate was
71.6% after 6 months and 62.2% after 12 to 24 months of treatment.
Argon versus selective laser trabeculoplasty: Purpose: To
compare argon laser trabeculoplasty (ALT) with selective trabeculoplasty
(SLT) in terms of their efficiency in lowering the intraocular
pressure. Results: A similar hypotensive efficacy was found
between ALT (-19%) and SLT (-17.9%). Conclusions: The short-term
efficacy of ALT and SLT was similar. In this study, patients
with PDG who underwent SLT showed a paradoxical rise in IOP.
This finding may indicate that even lower energies are required
when performing SLT in patients with heavily pigmented trabeculae.
Aqueous shunts for glaucoma: Conclusions: To date, there
is no evidence of superiority of one shunt over another.
The cost-effectiveness of bimatoprost,
latanoprost and timolol in treatment of primary open-angle
glaucoma in five European countries: Conclusion:
First-line treatment of latanoprost is dominated in all countries.
In four out of five countries, the timolol first-line therapy
with add-on latanoprost is also dominated. Based on this
pharmacoeconomic analysis, the most cost-effective strategy
seems to be timolol first line with add-on latanoprost if
target is not met after 3 months.
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