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A Continuing Education Review for Optometrists from the New England College of Optometry
Normal Tension Glaucoma
Murray Fingeret, OD, FAAO
Many glaucoma patients have normal intraocular pressure,
indicating that other factors are contributing to their disease.
Lacking the red flag of elevated IOP, optometrists need to maintain
a high index of suspicion for normal tension glaucoma so that
patients can be diagnosed and receive treatment to prevent
progression.
Among patients with glaucoma,
30% or more have intraocular pressures (IOPs) within a so-called “normal” range; and among certain glaucoma subpopulations, such as ethnic
Japanese, “normal” IOP rates are even
higher.1,2 Without the most common
indicator of glaucoma—high IOP—nor-
TARGET AUDIENCE This educational activity is intended for
optometrists.
LEARNING OBJECTIVES Upon completion of this activity,
participants will be able to:
1.Differentiate normal tension from high tension glaucoma.
2.Conduct an appropriate workup to diagnose normal tension
glaucoma.
3.Identify early glaucomatous damage on visual field based on
established guideline for minimal glaucomatous defect.
4.Properly stage glaucoma using the AGS severity scale.
EDITORIAL COMMITTEE
Baharak Asefzadeh, OD, MS, FAAO, is an adjunct assistant
professor of optometry at the New England College of Optometry
and director of the VA Boston Optometric Research Fellowship.
Tony Cavallerano, OD, FAAO, is an adjunct professor of optometry at the New England College of Optometry, where he is also
the director of professional relations and the executive director
of clinical training and patient care.
Mark T. Dunbar, OD, FAAO, is the director of optometric services
and optometry residency supervisor at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine.
Key Issues in Glaucoma Management: A Review for Optometrists
is sponsored by the New England College of Optometry and
supported by an unrestricted educational grant from Bausch +
Lomb, Inc. This publication is administered by an independent
editorial committee.
© 2016 Candeo Clinical/Science Communications, LLC. All rights
reserved. Neither the New England College of Optometry nor
Candeo Clinical/Science Communications, LLC, assumes any
responsibility for injury or damage to persons or property arising
from the use of information or ideas contained in this publication.
COURSE DIRECTOR
Tony Cavallerano, OD, FAAO
New England College of Optometry
Boston, MA, USA
mal tension glaucoma (NTG) is harder
to detect and, in several important
ways, more challenging
to manage than glaucoma associated with
elevated IOP. This review
will examine ways in
which normal tension
and high tension glaucoma differ and outline
a management strategy
for optimal detection
and management of
normal tension variants.
ING
INU
NT
CO
EDUC
AT
IO
N
CE
Issue 3
21 mm Hg.5 However, the authors
cautioned against misinterpreting their
data to mean that IOP above that level
indicated clinical abnormality.
As early as the 1960s, researchers
were aware that factors beyond IOP
likely contributed to glaucoma development. For example, Armaly observed
that a majority of individuals with
IOP greater than 21 mm Hg did not
develop glaucoma over the course of
the 7 years,6 nor were patients with low
IOP immune to developing glaucoma.
What Is Normal?
As convenient as it
would be to have one,
there is no hard and
fast line between normal and abnormal IOP.
Figure 1 A disc hemorrhage is seen at 7 o’clock, along
Studies conducted in
with a wedge shape retinal nerve fiber layer (RNFL) defect.
The disc hemorrhage borders the RNFL defect. Also note
the 1950s in the general
that there is focal neuroretinal rim loss inferiorly.
population found that
IOPs ranged between 13
and 30 mm Hg, with an average of 19
The lack of a distinct boundary
mm Hg.3 Other studies showed average
between “normal” and “elevated” IOP
IOP in the general population of 15-16
is further complicated by significant
mm Hg by applanation and 16-17 mm
variability in IOP measurement beHg by Schiotz tonometry.4 The idea of a
“normal” IOP originated with population studies conducted by Hollows and
More INSIDE:
Graham in the 1960s showing that
Visual Field Testing for Glaucoma
2.5% of the general population (two
Leo Semes, OD, FAAO
standard deviations above the mean)
had intraocular pressures greater than
To take the test online and obtain CE credit for this activity, go to
http://www.neco.edu/academics/continuing-education/online-ce/key-issues-glaucoma
Key Issues
in Glaucoma
Supported by an unrestricted
educational
grant fromManagement Bausch + Lomb, Inc.1
tween IOP-measuring devices, between
operators, and between days or even
different times on the same day.
Beyond IOP
Rather than relying on an arbitrary
cutoff point between normal and high
tension glaucoma, we can conceive of
glaucoma risk as a continuum. Cutoff
points give the erroneous impression of
a clean division between two populations: one that is at risk and one that
is not. But this is somewhat misleading. Barring certain acute conditions,
there is no pressure so high that every
patient with it will develop glaucoma,
nor is there any sustainable pressure so
low that the patient has absolutely no
chance of developing glaucoma. Furthermore, focusing on an IOP cutoff
point can make it seem as if IOP is the
sole risk factor, which is not the case.
Beyond IOP, factors that may be
involved in glaucoma pathogenesis
include optic nerve sensitivity, nonIOP pressure dynamics (eg, perfusion
pressure, translaminar pressure), and
immunologic factors. Indeed, what
Key Issues in Glaucoma Management — Issue 3
STATEMENT OF NEED
Glaucoma, a group of ocular diseases characterized by progressive damage to the optic nerve, is the second leading cause of
blindness worldwide. It affects a significant and growing portion
of the US population.1,2
CREDIT DESIGNATION STATEMENT
The New England College of Optometry designates this activity
for a maximum of 1 hour of COPE-approved continuing education
credit. Clinicians should only claim credit commensurate with the
extent of their participation in the activity.
As primary eyecare providers, medical optometrists are well
positioned to identify patients at risk and to diagnose, monitor,
and treat glaucoma. However, given that the expanded scope
of practice incorporating glaucoma treatment is relatively new,
many optometrists lack confidence in their ability to treat this
potentially blinding disease. In order to instill confidence and
help optometrists make sound clinical judgments about the care
of glaucoma patients, Key Issues in Glaucoma Management
will help optometrists better understand the various aspects
and nuances of the disease, including our current understanding of the role of intraocular pressure (IOP) in glaucomatous
optic nerve damage. Course content will also include current
rationale on glaucoma diagnosis and evidence-based strategies for reducing IOP.
EDITORIAL COMMMITTEE DISCLOSURE STATEMENTS
Baharak Asefzadeh, OD, MS, FAAO, is an adjunct assistant
professor of optometry at the New England College of Optometry
and director of the VA Boston Optometric Research Fellowship.
She has no financial disclosures related to this activity.
Each installment of Key Issues in Glaucoma Management will
look at an important topic in glaucoma diagnosis or therapy.
Each issue will build from a basic level to instill understanding
and confidence in medical optometrists. Key Issues in Glaucoma
Management aims to support optometrists’ clinical reasoning and decision-making abilities and help them turn medical
management of glaucoma into a vital segment of their practices.
REFERENCES
1.Resnikoff S, Pascolini D, Etya’ale D, et al. Global data on visual
impairment in the year 2002. Bull World Health Organ. 2004
November;82(11):844-51.
2.Eye Diseases Prevalence Research Group. Prevalence of
open-angle glaucoma among adults in the United States. Arch
Ophthalmol. 2004;122:532-8.
OFF-LABEL USE STATEMENT
This work may discuss off-label uses of medications.
GENERAL INFORMATION
The New England College of Optometry designates this activity
for a maximum of 1 hour of COPE-approved continuing education
credit. There is no fee to participate in this activity. In order to
receive CE credit, participants should read the report and then
take the posttest. A score of 70% is required to qualify for CE
credit. Estimated time to complete the activity is 60 minutes.
DATE OF ORIGINAL RELEASE February 2016. Approved for a
period of 24 months.
ACCREDITATION STATEMENT
This activity has been planned and implemented through the
joint sponsorship of the New England College of Optometry
and Candeo Clinical/Science Communications, LLC. The New
England College of Optometry is accredited by The Council on
Optometric Practitioner Education® (COPE® ), created by the Association of Regulatory Boards of Optometry (ARBO) to accredit
continuing education on behalf of optometric licensing boards.
2 Key Issues in Glaucoma management
Tony Cavallerano, OD, FAAO, is an adjunct professor of optometry at the New England College of Optometry, where he
is also the Director of Professional Relations and the Executive
Director of Clinical Training and Patient Care. He has no financial
disclosures related to this activity.
Mark T. Dunbar, OD, FAAO, is the director of optometric services
and optometry residency supervisor at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine. He states that
in the last 12 months, he has been a consultant for Allergan and
has participated in advisory boards for Carl Zeiss, Regeneron
Pharmaceuticals, Inc., Bio-Tissue, ArcticDx, and B&L Nutrition.
AUTHOR DISCLOSURE STATEMENT
Murray Fingeret, OD, is chief of the optometry section, Department of Veterans Affairs, New York Harbor Health Care System,
Brooklyn Campus, and clinical professor, SUNY College of
Optometry. He is a consultant for Alcon, Aerie, Allergan, Bausch
+ Lomb, Carl Zeiss Meditec, Diopsys, Heidelberg Engineering,
and Topcon.
Leo Semes, OD, FAAO, is professor of optometry at the
University of Alabama at Birmingham School of Optometry in
Birmingham, AL. Dr. Semes is a consultant, advisor, or speakers’
bureau member for Alcon, Allergan, ArcticDx Inc., and OptoVue.
He is also a stock shareholder for High Performance Optics.
DISCLAIMER
Participants have an implied responsibility to use the newly
acquired information to enhance patient outcomes and professional development. The information presented in this activity
is not meant to serve as a guideline for patient care. Any procedures, medications, or other courses of diagnosis or treatment
discussed or suggested in this activity should not be used by clinicians without evaluation of their patients’ conditions and possible
contraindications or dangers in use, applicable manufacturers’
product information, and comparison with recommendations
of other authorities.
COMMERCIAL SUPPORTERS
This activity is supported by an unrestricted educational grant
from Bausch + Lomb, Inc.
we call “glaucoma” is probably a collection of interrelated (or perhaps
dissimilar) diseases with a common
endpoint of optic nerve damage.
Translaminar pressure (TP), the
pressure across the lamina cribrosa,
is a gradient that is thought to enable
maintenance of normal structure
and function of the optic nerve.7 The
lamina cribrosa is a series of channels
in the optic nerve that allows the fibers
of the optic nerve to pass from inside
the eye back toward the brain. Having
a low TP, even if IOP is also low, may
be a risk factor for NTG.7 Translaminar
pressure is based on cerebrospinal fluid
pressure (CSFP), which is assessed by
spinal tap, an invasive procedure not
practical in everyday clinical practice.
Thus, TP remains a variable that is, for
the time being at least, confined to research investigation. However, as more
is learned about the role of CSFP and
TP in the pathogenesis of NTG, there
is increased possibility for research
into much needed novel therapeutic
approaches beyond IOP lowering.
Hidden Hypertension
Before a patient is identified as
having NTG, efforts should be made
to detect elevations in IOP that may
be present but undetected. IOP tends
to fluctuate throughout the day and
night and with varying body positions;
sleep studies have observed that IOP
may peak in early morning. Assessing
IOP at multiple times throughout the
day can help uncover diurnal fluctuations in IOP, including high IOP not
observed at the initial check.8
In addition, systemic medications,
specifically oral beta-blockers for the
treatment of cardiovascular hypertension, can lower IOP as an unintended
side effect. It is important to maintain
up-to-date medical and medication
histories as a matter of good practice
and in order to identify treatments that
might affect IOP.
Lastly, using the transcorneal IOP
assessment methods currently available to us, IOP may read falsely low
in eyes with thin central corneas. And
IOP may be falsely high across thicker
than average central corneas. It is,
To take the test online and obtain CE credit for this activity, go to
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therefore, good practice to measure
central corneal thickness in conjunction with initial IOP testing to be sure
that IOP determination is not influenced by unusual pachymetry.
the PatIeNt eValuatIoN
When IOP is “normal,” eyecare
providers should be on the lookout for
sometimes subtle physical examination findings consistent with NTG.
Although there is overlap with hypertensive glaucoma, features commonly
seen in association with NTG include
optic disc hemorrhages (flame-shaped
or splinter hemorrhages) on the inferior
or superior temporal disc border, optic
nerve cupping with focal loss of the rim,
and peripapillary atrophy surrounding
the edges of the optic disc (Figure 1).
Optical coherence tomographic (OCT)
images should be obtained to record
and follow the appearance of the optic
nerve (Figure 2). Of course, visual fields
and IOP should be assessed.
Serial IOP checks can be conducted
at different times on different days or
every 2 hours on the same day. Studies have shown that IOP assessment
outside of normal office hours can be
useful in discovering otherwise hidden IOP elevations.8 For patients with
elevated IOP, gonioscopy should be
performed to rule out a closed angle
or other outflow obstruction. And, as
noted, pachymetry is helpful for assuring that IOP measurement is accurate.
PerfusIoN Pressure
It is important to include blood
pressure measurement as part of the
exam when glaucoma is suspected in
order to calculate perfusion pressure
(PP). When low, this is a red flag for
glaucoma risk. Perfusion pressure is calculated by subtracting the highest IOP
from the lowest diastolic pressure. For
example, if the blood pressure is 120/80
mm Hg and IOP is 20 mm Hg, the PP is
80 – 20 or 60 mm Hg, which is good. If,
Figure 2 The field of the optic nerve seen in Figure 1. A visual field defect often
associated with glaucoma is seen with the superior defect running through fixation.
To take the test online and obtain CE credit for this activity, go to
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Core CoNCePts
● NTg is likely part of a continuum
of open-angle glaucomas.
● NTg is an indication that factors
in addition to iOP are important
in glaucoma pathogensis.
● All patients with normal iOP
need a careful examination of
the optic nerve to rule out early
or subtle changes consistent
with NTg.
● Management of NTg is similar to
other open-angle glaucomas.
on the other hand, the patient’s blood
pressure is lower, for example 90/60
mm Hg, and IOP is 15 mm Hg, the PP
is 45 mm Hg, which is less favorable. As
a rough guideline, PP that is lower than
50 mm Hg is concerning and lower
than 30 mm Hg is very concerning.
How low blood pressure may
contribute to glaucoma pathophysiology remains unclear. Raynaud’s phenomenon is a vasospastic condition
characterized by relatively low blood
pressure, cold extremities, and thin
body habitus that is more common in
women and is associated with higher
than average rates of NTG.9 This association points to a likely vascular
component, perhaps hypoperfusion of
optic nerve tissue, in the pathophysiology of NTG. Low nocturnal blood pressure is more prevalent in those with
NTG.10 In some cases, it may be useful
to discuss with a patient’s primary
care provider whether to switch blood
pressure medication from nighttime
administration to morning to potentially reduce nocturnal hypoperfusion
of the optic nerve.
Another comorbidity to bear in
mind when evaluating patients with
glaucoma is obstructive sleep apnea,
which has been shown to increase risk
for NTG.11,12 A sleep study to rule out
sleep apnea is appropriate and may be
useful in patients with normotensive
glaucoma who also exhibit signs or
symptoms of sleep apnea.
treatmeNt
As with other forms of open-angle
Key Issues In Glaucoma manaGement 3
glaucoma, treatment of NTG centers
on IOP reduction. It is reasonable to
start treatment with a topical ocular
prostaglandin analog and follow patients closely for adequate response,
aiming for about 30% IOP reduction.
One new agent, latanoprostene bunod,
which is not approved in the US but is
in phase III clinical trials, combines
the PGA latanoprost with a nitric
oxide-donating moiety and may have
a positive impact on PP as well as on
IOP. I often recommend regular exercise (eg, walking 20 minutes per day)
to my patients as an adjunct for IOP
lowering.13 Additionally, while there is
a paucity of literature linking smoking
to glaucoma, I will often recommend
smoking cessation classes to my patients who smoke.
In my experience, it is easier to
achieve substantial IOP reduction
when IOP is elevated compared to
when it is normal or low, so aggressive
IOP reduction therapy and monitoring
at least as intensively as for hypertensive glaucoma is appropriate. For
patients unresponsive to a maximum
of three medications (two bottles with
4 Key Issues in Glaucoma Management
one bottle a fixed combination), my
practice is to refer for selective laser
trabeculectomy or even surgical intervention if progression is continuing.
Conclusion
Normal tension glaucoma is a
common and uniquely challenging
clinical variant (or group of variants)
of glaucoma. Glaucoma patients with
normal IOP need careful retinal examinations and aggressive IOP-lowering
therapy and follow-up. As research on
glaucoma continues, new insights into
the non-IOP parameters that contribute to glaucoma will likely emerge and
open the door to new treatments.
Murray Fingeret, OD, is chief of the optometry
section, Department of Veterans Affairs, New York
Harbor Health Care System, Brooklyn Campus, and
clinical professor, SUNY College of Optometry. He
is a consultant for Alcon, Aerie, Allergan, Bausch +
Lomb, Carl Zeiss Meditec, Diopsys, Heidelberg Engineering, and Topcon. Medical writer Noelle Lake,
MD, assisted in the preparation of this manuscript.
REFERENCES
1. Anderson DR. Normal tension glaucoma. Ind J
Ophthalmol. 2011;59(Suppl 1):S97-101.
2. Pekmezci M, Vo B, Lim AK, et al. The characteristics of glaucoma in Japanese Americans. Arch
Ophthalmol. 2009;127:167-71.
3. Alimuddin M. Normal intra-ocular pressure. Br J
Ophthalmol. 1956 Jun;40(6):366-72.
4. Armaly MF. The Des Moines population study of
glaucoma. Invest Ophthalmol. 1962;1:618.
5. Hollows FC, Graham PA. Intra-ocular pressure,
glaucoma, and glaucoma suspects in a defined
population. Br J Ophthalmol. 1966;50:570-86.
6. IOP and Tonometry. http://eyewiki.aao.org/
IOP_and_Tonometry. Accessed on October 21,
2015.
7. Jonas JB. Role of cerebrospinal fluid pressure in
the pathogenesis of glaucoma. Acta Ophthalmol.
2011;89:505-14.
8. Arora T, Bali SJ, Arora V, et al. Diurnal versus officehour intraocular pressure fluctuation in primary
adult onset glaucoma. J Optom. 2015;8:239-43.
9. Konieczka K, Ritch R, Traverso CE, et al. Flammer
syndrome. EPMA J.2014;5:11.
10. Hayreh SS, Zimmerman MB, Podhajsky P, Alward
WL. Nocturnal arterial hypotension and its role
in optic nerve head and ocular ischemic disorders.
Am J Ophthalmol. 1994;117(5):603-624.
11.Sergi M, Salerno DE, Rizzi M et al. Prevalence of
normal tension glaucoma in obstructive sleep apnea syndrome patients. J Glaucoma. 2007; 16:42-6.
12. Bendel RE, Kaplan J, Heckman M et al. Prevalence
of glaucoma in patients with obstructive sleep
apnea – a cross-sectional case-series. Eye. 2008;
22:1105-9.
13.Passo MS, Goldberg L, Elliot DL, et al. Exercise
training reduces intraocular pressure among
subjects suspected of having glaucoma. Arch
Ophthalmol. 1991;109:1096-8.
To take the test online and obtain CE credit for this activity, go to
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Visual Field Testing for
Glaucoma
LEo SEMES, od, Faao
Visual field testing serves as the primary method for detecting and
evaluating functional loss and progressive damage from glaucoma,
but its clinical value depends heavily on obtaining good data.
Visual field testing measures the
ability of a patient to detect stimuli of
varying brightness throughout the field
of vision. In glaucoma, where loss of
central visual acuity occurs late, visual
sensitivity testing within the central
30 degrees is the primary method of
assessing a patient’s visual function.
Visual field results are typically used
to support a glaucoma diagnosis by
identifying the initial functional loss
and to establish a baseline to guide
management on subsequent visits.
Visual fields can also help guide treatment by providing an index of stability
or progression for patients on treatment to lower IOP. Most of today’s
visual field instruments are equipped
with event- and trend-based programs
for progression analysis, allowing us to
assess the stability of the patient’s disease over time and determine whether
treatment needs to be more aggressive.
ClINICal PerImetry
The most commonly used visual
field test is standard automated perimetry (SAP), a computerized threshold
test with a static white stimulus presented on a white background. SAP
measures primarily the central 30
degrees of fixation. Light sensitivity
within this region reflects the function
of the majority of retinal ganglion cells
and over 83% of the visual cortex.1
Among several stimulus presentation
patterns, two are standard in visual
field analysis in glaucoma: 30-2 (76
points within 30 degrees of visual
field) and 24-2 (54 points within 24
degrees of the visual field but retaining
the two outermost nasal points from
30-2, which are particularly sensitive
to early change in glaucoma). Because
of its shorter testing time and lower error rate, 24-2 has become established
as the test of choice in glaucoma.
Researchers have recently found
that early glaucomatous damage
commonly affects the macula,2 which
represents a small portion of the central field of vision (about 8 degrees
in diameter) but contains about one
third of the retinal ganglion cells.1
This finding suggests that a 10-2 test
may be of particular value in detecting early glaucomatous changes. The
10-2 pattern tests the same number
of points as the 24-2 but is limited to
the central 10 degrees of visual field.
On the 10-2 tests, points are within
2 degrees of each other, whereas the
separation of test points on the 24-2
field is 6 degrees. The closer proximity
of the test stimulus on a 10-2 allows
for the detection of early defects that
might not be seen on a 24-2 test. The
dense test pattern can be extremely
tedious for patients, and its clinical
application is not yet established.
In the US, the most widely used
instrument for visual field testing is
the Humphrey Field Analyzer (Carl
Zeiss Meditec Inc., Dublin, CA). The
preferred test program for diagnosing
and monitoring glaucoma is the Swedish Interactive Threshold Algorithm
(SITA) Standard, an algorithm also
widely used in clinical trials. Developed
to shorten test time, the SITA algorithm takes into account information
gathered from surrounding locations
as well as responses at each point when
calculating threshold values.3,4
glauComatous VIsual
fIeld loss
Visual field defects in glaucoma
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Core CoNCePts
● Visual field testing can provide
invaluable diagnostic information
on functional visual loss.
● SAP, a computerized, threshold
static test, has been the
mainstream test in glaucoma
management. it measures
differential light sensitivity of
the central visual field, primarily
within the central 30 degrees of
fixation.
● The SiTA Standard in 24-2
pattern is the test most often
used for routine visual field
examination in glaucoma.
● The goal of a visual field test is to
search for indicators of departure
from normal light sensitivity.
The diagnosis of glaucoma
can be made using any of the
following three measures: the
pattern standard deviation, the
glaucoma hemifield test, and
point-wise analysis of the pattern
deviation plot.
● glaucomatous visual field
damage is classified as mild,
moderate, or severe, based
primarily on the extent and
location of the defect(s).
● Artifacts and variable results
are fairly common in visual
field testing. Before making
the diagnosis of glaucoma
or determining true disease
progression, it is important to
confirm suspected changes by
repeat testing.
result from axonal loss in the retinal
nerve fiber layer secondary to damage
at the optic nerve head. Accordingly,
a visual field defect should reflect the
pattern of nerve fibers in the affected
retinal area. As the superior and inferior poles of the optic nerve are most
susceptible to glaucomatous damage,
visual field progression in glaucoma
typically begins with the superior and
inferior arcuate fibers. There are three
established criteria for determining
early damage: a cluster of three or more
significantly depressed points (outside
the 95% statistical range considered to
be normal) on a pattern deviation plot;
Key Issues In Glaucoma manaGement 5
abnormal glaucoma hemi-field test;
and an abnormal pattern standard deviation value (again, outside the 95%
statistical range of normal). Pattern
standard deviation may be the most
important index when looking for
very early changes, but the diagnosis
of glaucoma should be considered if
any one of the three criteria is met, on
repeated testing.
The severity of the visual field
defect, an indicator of the degree of
functional damage, may be used to
determine the aggressiveness of initial
therapy and, in established patients,
to assess the effectiveness of ongoing
IOP-lowering treatment. Several severity grading systems have been proposed
and used in different clinical trials.5
The severity scale incorporated in
ICD-9 and ICD-10 coding for staging
glaucoma was developed in 2011 by
an American Glaucoma Society (AGS)
work group based on the extent of the
visual field defect and its proximity to
fixation.6
In the AGS staging system, sever-
ity of glaucoma (measured in the
more affected eye) is graded using
the following definitions: 1) mild or
early-stage: optic nerve changes consistent with glaucoma but no visual
field abnormalities on any visual field
test or abnormalities present only on
short-wavelength automated perimetry or frequency doubling perimetry;
2) moderate-stage: optic nerve changes
consistent with glaucoma and glaucomatous visual field abnormalities
in one hemi-field and not within 5
degrees of fixation; and 3) severe- or
advanced-stage: optic nerve changes
consistent with glaucoma and glaucomatous visual field abnormalities in
both hemi-fields and/or loss within 5
degrees of fixation in at least one hemifield (Figures 1, 2, and 3).6
Differential Diagnosis
When analyzing perimetry results,
it is important to recognize that glaucoma is only one of many possible
causes of visual field defects. Visual
field abnormalities may result from
Figure 1 Moderate but not consistently repeatable visual field
depressions in a 76-year-old ocular hypertensive patient. The
lack of repeatability is due to fixation losses.
6 Key Issues in Glaucoma Management
damage anywhere along the visual
pathway, from retina to cortex. The
visual field patterns of nonglaucomatous retinal or neurological conditions,
however, often differ from that of
glaucoma. Tissue damage to the outer
retina, for example, will cause defects
that may or may not respect either the
horizontal or vertical midline. Usually
these defects are limited to just one eye,
and the local pathologies (eg, retinal
vascular occlusions) are visible on
fundoscopy. In contrast, visual field damage
from neurological disorders affecting
the brain (eg, a brain tumor or stroke)
is bilateral (in most cases) and presents
in a characteristic pattern. Usually it is
a defect respecting the vertical meridian, with a distinct pattern of dense
depressions. Post-chiasmal lesions,
for example, generally result in defects
confined to the contralateral visual
hemifield, while pituitary tumors affecting the middle portion of the optic
chiasm are known to cause bitemporal
hemianopsia.
Figure 2 Severe visual field defects in a patient who also has
anterior ischemic optic neuropathy (AION). Central depressions,
as well as depressions in both superior and inferior hemispheres,
can be seen.
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a high level of
attention during
the test, which
can be fatiguing
to the patient.
Some patients
tend to do better
on the test than
others, but even
good test-takers
have aberrant results from time
to time.
Today’s perimetry software,
whether for diagnosis or analysis
of visual field
progression, has
become highly
robust. But no
matter how robust or innovative the software,
it ultimately
must rely on input from the patient. Most clinicians do not perform the visual
Figure 3 Trend and event analysis showing stability over a
field examinadecade in a 54-year-old female glaucoma suspect. The event
tion themselves.
graph (lower panel) indicates a single point of likely progression
(filled triangle) and three sporadic points that are flagged for the
This makes it
first time. All of these points are isolated and not indicators of
critical to have
glaucomatous; the picture is consistent with a stable optic nerve
a well-trained
appearance.
and experienced
technician as test
administrator. Careful test administraTest Variability
tion is important not only for field
To appropriately interpret visual
analysis but also for practical reasons.
field results, it is important to underIn many practices, clinicians can be restand the test’s limitations. Perimimbursed for no more than one visual
etry is based on identification of any
field test per year. If the data collected is
variation from normal, yet the most
of poor quality, the doctor will have to
important problem with perimetric
either wait another year or repeat the
data is its variability. A patient’s first
test in order to establish the patient’s
visual field tests often show defects that
disease status. When it is in the best
disappear on repeat testing. By nature
interest of the patient, this should be
subjective and susceptible to random
done regardless of reimbursement,
variations and artifacts, visual field
which varies by jurisdiction.
testing requires the subject to maintain
To take the test online and obtain CE credit for this activity, go to
http://www.neco.edu/academics/continuing-education/online-ce/key-issues-glaucoma
Explaining the test process carefully to first-time patients may help
prevent unnecessary mistakes. Repeat
testing can effectively minimize variability and improve accuracy in recognizing the presence or progression
of visual field damage.7 What is most
important, however, is to interpret observed changes in light of other clinical
findings. Typically, visual field changes
in glaucoma patients correlate well
with structural changes in the optic
nerve and the retinal nerve fiber layer
that are observable on clinical examination or imaging studies. If glaucoma
is an elephant, then the best way for
us to sidestep the fate of the six blind
men is to look at all aspects of clinical
assessment.
Leo Semes, OD, FAAO, is professor of optometry at
the University of Alabama at Birmingham School
of Optometry in Birmingham, AL. Dr. Semes is a
consultant, advisor, or speakers’ bureau member
for Alcon, Allergan, ArcticDx Inc., and OptoVue.
He is also a stock shareholder for High Performance
Optics. Medical writer Ying Guo, MBBS, assisted
in the preparation of this manuscript.
REFERENCES
1. Harwerth RS, Quigley HA. Visual field defects and
retinal ganglion cell losses in patients with glaucoma. Arch Ophthalmol. 2006 Jun;124(6):853-9.
2. Hood D, Raza A, de Moraes C, et al. Glaucomatous
damage of the macula. Prog Retina Eye Res. 2013;
32:1-21.
3.Bengtsson B, Olsson J, Heijl A, Rootzén H. A
new generation of algorithms for computerized
threshold perimetry, SITA. Acta Ophthalmol
Scand. 1997;75(4):368-75.
4. Budenz DL, Rhee P, Feuer WJ, McSoley J, Johnson
CA, Anderson DR.Sensitivity and specificity of
the Swedish interactive threshold algorithm for
glaucomatous visual field defects. Ophthalmology.
2002;109(6):1052-8.
5.Brusini P, Johnson CA. Staging functional damage in glaucoma: review of different classification
methods. Surv Ophthalmol. 2007;52(2):156-79.
6.Fellman RL, Mattox CG, Ross KM, Vicchrilli S.
Know the new glaucoma staging codes. Available
at: http://www.aao.org/eyenet/article/knownew-glaucoma-staging-codes?october-2011
7.Schulzer M. Errors in the diagnosis of visual
field progression in normal-tension glaucoma.
Ophthalmology. 1994;101(9):1589-94; discussion
1595.
Key Issues in Glaucoma Management 7
Examination Answer sheet — Key Issues in Glaucoma Management — Issue 3
This CE activity is sponsored by the New England College of Optometry and
is supported by an unrestricted educational grant from Bausch + Lomb, Inc.
Submit your answers to the below test online by visiting http://www.neco.edu/
academics/continuing-education/online-ce/key-issues-glaucoma. You may
also access the online test by scanning the QR code on the right. The New
England College of Optometry designates this activity for a maximum of 1 hour of
COPE-approved continuing education credit. There is no fee to participate in this
activity. In order to receive CE credit, participants should read the report and then
take the posttest. A score of 70% is required to qualify for CE credit. Estimated
time to complete the activity is 60 minutes. CE exam expires January 31, 2017.
1.Elevated IOP can be missed
on a single visit because:
A.It is temporarily low
due to normal diurnal
fluctuation
B.The patient was
recently lying down
C.The patient has a
normal trabecular
meshwork
D.All of the above
2.Which of the following
is a likely cause of
simultaneous loss of
temporal visual field in
both eyes?
A. Pituitary tumor
B. Stroke
C. Glaucoma
D. Retinal vascular
occlusion
3.Ocular perfusion pressure
is determined by which of
the following formulas?
A. Cerebrospinal fluid
pressure divided by IOP
B.Two times systolic
blood pressure minus
diastolic pressure
C. Translaminar pressure
minus IOP
D. Diastolic blood
pressure minus IOP
4.Within the glaucoma
patient population, the
proportion of patients with
normal tension glaucoma
is about:
A. 0.3%
B. 3%
C. 30%
D. 63%
5.On the AGS severity scale,
which of the following is
most consistent with mild
or early stage glaucoma?
A. Optic nerve
changes consistent
with glaucoma and
glaucomatous visual
field abnormalities
B.Visual loss within 5
degrees of fixation in at
least one hemi-field
C.Optic nerve changes
consistent with
glaucoma but no visual
field abnormalities
D. None of the above
6.Which of the following is
the preferred test pattern
for routine visual field
testing in glaucoma?
A. 60-4
B. 30-2
C. 24-2
D. 10-2
7.Appropriate treatments for
normal tension glaucoma
may include:
A. High-dose topical
steroid
B. Ocular hypotensive
medication(s)
C.Cessation of daily
NSAID usage
D. Oral omega-3
supplements
8.Which of the following
is the major weakness
of visual field testing
according to Dr. Semes?
A. It’s time-consuming
B. It’s expensive
C.It’s too complex—
clinicians can’t
understand it
D.It’s subjective and
results can be variable
9.Armaly observed that:
A.Most eyes with IOP
> 21 mm Hg do not
develop glaucoma
within 7 years
B.65% of eyes with IOP
> 21 mm Hg develop
glaucoma in 7 years
C.Glaucoma is common
in patients with
obstructive sleep apnea
D.None of the above is
true
10.According to Dr. Semes,
which of the following is a
factor that has significant
influence on the quality of
perimetric data obtained?
A.The clinician who
reviews the data
B.The test administrator
C.The manufacturer of
the testing instrument
D.All of the above
8 Key Issues in Glaucoma management
To take the test online and obtain CE credit for this activity, go to
http://www.neco.edu/academics/continuing-education/online-ce/key-issues-glaucoma