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Glaucoma - Visual Fields
• Program Strategies
• Perspectives on Perimetry
• Visual Field Interpretation
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Foundational guidelines
Catch trials
Grey scale
Total and Pattern deviation
Glaucoma hemifield test
Global indices
Summary
• Plaquenil Visual Field Testing
Zeiss-Humphrey Visual Field
Program Strategies of HFA-II
Full Threshold
Standard
Fastpac
SITA- Standard
SITA- Fast
30-2 or 24-2 Tests
Standard Automated Perimetry
(white on white)
“Although different structural and functional tests
are used to diagnose and monitor glaucoma,
standard automated perimetry (SAP) remains the
most widely used methods to assess visual
function loss.”
Reference: Ophthalmology, January 2010
Swedish Interactive
Thresholding Algorithm (SITA)
SITA Standard: Twice as fast as “full threshold”
algorithm
SITA Fast: Twice as fast as “Fastpac”
Requires a powerful computing system (only for
HFA-II)
Intuitive and artificial intelligence is the key
element
Constant monitoring allows patient to set pace of
stimuli
Short Wavelength Automated
Perimetry (SWAP) (SITA-SWAP)
• Uses blue target on bright yellow background
• Theorized to detect functional loss earlier than
white on white
• Can be used with an HVF-II units only
• Advise to look for:
• localized color change (from yellow to violet)
• an achromatic spot
• If patient has 20/30 or worse NS, use W on W
• If patient is felt to have moderate to advanced
glaucoma, use white on white
• SITA-SWAP-much enhanced but clinical value is
debated
SITA-SWAP VS SITA-FAST
• “Bengtsson and Heijl, Ophthalmology, July 2006.
• “Surprisingly, there was no significant difference
between conventional SAP and the 2 SWAP
programs in diagnostic sensitivity.”
• “SITA-Fast has previously been reported to be able
to identify at least as much significant glaucomatous
field loss as SITA Standard . . . and to have a
diagnostic sensitivity of more than 90%.”
• “Our results indicate that there may be some
differences in sensitivity between SWAP and SAP,
but that those differences are probably smaller than
what has been believed previously.”
• SWAP 12 min - - SITA-SWAP 4.1 min - - SITA-Fast 3.5
min.
SAP vs SWAP
• Of 416 patients, 15% were “high risk” for POAG
• Only about half of this 15% converted
• Despite its limitations, SAP has become a standard in
clinical care across the world. SWAP, however, has never
gained such widespread acceptance.
• It is possible that SITA SWAP will prove to be useful for
early detection of glaucomatous conversion. To date, there
is insufficient evidence for that. We therefore recommend
that clinicians use SAP rather than SWAP in their daily
practices to detect early glaucomatous conversion in OHT.
• Although early SWAP visual field defects have been
suggested typically to precede those in SAP in conversion
from OHT to POAG, our prospective, longitudinal follow-up
study does not support this suggestion. On the contrary,
SAP appears to be at least as sensitive to conversion as
SWAP in a majority of eyes.
Reference: Ophthalmology, January 2010
Frequency Doubling Technology
• FDT isolates subset of retinal ganglion cell
mechanisms in the magnocellular (M-cell)
pathway. These M-cells have large diameter
fibers and comprise only 3% to 5% of all retinal
ganglion cells. The damage of these cells in the
disease process makes FDT efficient and
effective for the detection of visual field loss.
• Supra-threshold screening in 45 seconds. Full
threshold testing in under 4 minutes.
• Tests central 20-30 degrees; patient wears own
correction; normal room lighting
Debunking Myths
Once thought rare, optic disc hemorrhages occur in
most glaucoma patients.
It has been proposed that IOP fluctuations represent a
key risk factor for glaucoma progression, however,
there is no clear evidence to support this concept.
Another myth is that selective perimetric testing (such
as SWAP or FTD) can detect VF loss before standard
white-on-white perimetry.
Reference: International Glaucoma Review of the
World Glaucoma Association, Vol. 10, 2008
Humphrey Matrix
• 2nd generation frequency
doubling technology
• Original FDT: tests 17 points
with 10 degree targets
• Matrix 24-2 equivalent: tests 55 points with 5
degree targets
• Has 5 threshold tests: N-30, 24-2, 30-2, 10-2, and
macular test
• Has small footprint, easy to operate, floppy & CD
drives
• A close “second” to the Humphrey VF Analyzer
SITA vs Matrix Study
No significant difference in outcomes
“Each visual field test tended to identify different
subsets of eyes with glaucomatous-appearing optic
discs as abnormal.”
Functional changes in glaucoma detection may
differ significantly between individuals
Matrix perimetry may not detect more extensive
damage as compared to SITA
Reference: Archives of Oph., March 2007
Perspective On The Grey Scale
Only a general guide to field defects
Tested points are six degrees apart
The grey scale is an interpolation
Good for educating patients regarding their
individual field status
Show patient their grey scale mapping and then
one that is normal. This helps the patient
understand their status and need for compliant
medical therapy.
Total Deviation (TD)
• The point by point deviation from age-matched
normals
• Deviation threshold is +/- 5DB, depending on the
points location within the field
• Because of the increased precision of SITA
thresholding, deviation threshold is +/- 4 DB
• Displayed in a two-fold format:
• Actual numeric deviation from normal (? value)
• Probability of the response sensitivity being normal
(very valuable)
Pattern Deviation (PD)
• A refinement beyond total deviation
• Uses a representative point within the least
diseased portion of the field to establish a new,
more sensitive evaluation of the pattern of the
field defects
• Working as an “elevator of the entire hill of
vision, it will factor out generalized depression as
is commonly seen with cataracts, miotic pupils,
and inaccurate trial lenses.
• Also displayed in a two-fold format:
• Actual numeric deviation from normal (? value)
• Probability of the response sensitivity being normal
(very valuable)
Glaucoma Hemifield Test
• Assumes that glaucoma does not cause a
generalized global depression of the field of
vision
• Takes advantage of the asymmetric field loss
patterns generally seen in glaucoma
• Analyzes defects in the superior hemifield and
compares to mirror image locations in the inferior
hemifield
• Included in Standard Strategy, SITA, and SITAFast, but not in Fastpac
• Useful, but not critical data
The Global Indices
(MD)
(PSD)
Mean deviation
Pattern Standard Deviation
- These indices use a number to characterize the
visual field.
- Only the probability score beside the raw data
number has any importance. A probability score
appears next to the raw data number only if the
data deviates significantly from normal.
Mean Deviation (MD)
Simply the weighted average of how much the
patient’s overall function deviates from that of
age-matched normals.
General barometer of overall field depression (or
rarely elevation)
Pattern Standard Deviation (PSD)
Field loss in glaucoma is not diffuse, but rather
there are points, or clusters of points, that are
irregularly affected
These irregularities are seen as a “pattern” of field
loss
PSD is a characterization of localized change in the
visual field
When the patterns of field loss are significant, a
percent probability is given (P ranges from 10% to
0.5%)
Ultrasummary
• A combined cerebral assessment of:
• Pattern Deviation probability plots as compared to
Total Deviation probability plots
• Pattern Standard Deviation probability values
• These probability plots give the greatest VF data
guidance to the functional status of the patient’s
optic nerves
• Remember: ALWAYS CORRELATE THE
CLINICAL FINDINGS WITH THE VISUAL FIELD
STUDIES!
Perspective on Progression
“Because fluctuation in visual sensitivity is a
confounding factor, if a follow-up visual field test
discloses progression, it must be repeated at least
once – preferably twice – before you conclude that
the deterioration is indicative of true progression.
Most clinicians know from experience that patients
often exhibit apparent visual field progression on a
single test, only to have the next test clearly
demonstrate stability relative to the baseline visual
fields, and multiple clinical trials have confirmed
this.”
Rev of Ophthal, January 2008
Consensus on Visual Fields
“It was generally agreed that the noise level can be
very high in VF testing, an a high number of tests is
always required to reveal the true trend.”
When in doubt, Repeat the Field!
Ophthalmology, November 2007
Glaucoma Progression Analysis
A software program for Humphrey perimeters
Statistically analyses all points for progression
Can be immensely helpful in detecting VF
progression
Can be done both retrospectively and prospectively
A new standard in detecting progression
Available from Carl Zeiss-Meditec
Optic Nerve Head Image Analyzers
GDX-VCC, OCT, HRT, RTA, etc.
Can be helpful in early diagnosis
Limited value in advanced glaucoma
Excellent for detection of progression
A COMPONENT of the glaucoma evaluation
Not a “litmus test” for glaucoma
Imaging Technology in Glaucoma
“Given the substantial advances in glaucoma
imaging, it is important to remind clinicians that
current glaucoma diagnosis cannot be solely
instrument-based. Rather the imaging information
should be considered as being complementary to
other clinical measures.”
International Glaucoma Review of The World Glaucoma Association.
Volume 10-3 2008
Nerve Fiber Layer Analyzers
in Perspective
These so-called “objective” nerve fiber layer
scanning devices are only relatively objective
compared to highly subjective perimetry. Looking
at this next series of GDx scans very nicely
demonstrates this clinical truth.
Optic Nerve Imaging
“Given the variability of clinician documentation,
imaging may elevate the assessment of the optic
nerve by the general clinician, perhaps to the level
of a fellowship-trained expert.”
“The clinician who successfully integrates imaging
in practice compliments their clinical evaluation
and adjunctive testing.”
American Journal of Ophthalmology, April 2008
Optic Nerve Imaging
“Ongoing advances in imaging as well as
impracticalities associated with obtaining and
assessing optic nerve stereo photographs have
made imaging increasingly important.”
“These technologies “…should not mislead a
clinician to think that glaucoma diagnoses can be
solely machine-based at present. Rather, the
imaging information should be considered as being
complementary to other clinical measures.”
American Journal of Ophthalmology, April 2008
RNFL, Neuroretinal Rim, and
Visual Field Progression
• Regarding optic disc photos, “the agreement for
assessment of progressive optic disc changes is
poor even among glaucoma specialists.”
• RNFL is mostly ganglion cell axons, whereas
neuroretinal rim tissues contain nonneural structures
• Because rate of change within these two tissues may
vary with the stage of disease, interpretation of
progression should be evaluated on an individual
basis
• “It is plausible that detection of progression with
OCT RNFL thickness may not be as effective as
visual field measurement in moderate and advanced
glaucoma.”
Oph. August 2011
Treatment Goals For POAG
• Establish a target IOP below which optic nerve
damage is unlikely to occur
• Maintain an IOP at or below this target level with
appropriate therapy
• Monitor VF's and ONH appearance to refine the
adequacy of the target IOP
• Optimally balance the benefits of therapy with
any side effects
• Educate and engage patients in the management
of their disease
Diagnosis Does Not
Mandate Treatment
“Although decisions on treatment may not
necessarily be made at an early stage, other
appropriate measures, such as close monitoring,
may be considered. It was generally agreed that
early detection does not automatically imply early
treatment and that early detection and early
treatment should be considered separately.”
Reference: Ophthalmology, November 2007
When to Treat?
• “Patients with normal optic disc and visual field
could tolerate an IOP of 30 mmHg for many years
without need of treatment.”
• “What it comes down to is . . . treat young patients
who are in the high-risk group, and it is worth
watching the elderly in a low-risk group. The
problem remains what to do for those in the middle.”
Ref: A Sommer/Johns Hopkins Univ. Ophthalmology Times. Jan. 2011.
Melton-Thomas: All glaucoma doctors struggle with the
decision of whom to treat, and when. Remember: medical
care is an art, and equally well-trained doctors commonly
differ in clinical decision-making.
Factors Regarding Treatment Initiation
• Use of a “risk calculator”, and lack of glaucoma specialty
training were associated with physicians being more
likely to treat ocular hypertension
• 2 / 58 glaucoma specialists and 4 / 118 ophthalmologists
reported treating all patients with an IOP >21 mmHg
Most critical factors: IOP, C/D ratio, and CCT (both groups)
• Rational estimation of “risk of conversion” to OAG is
essential for proper clinical decision-making
• Treatment by default or faulty decision-making remains a
healthcare crisis in glaucoma patient care management
Reference: AJO, October, 2011
The Holy Grail in
Glaucoma Management
“At the most basic level we have yet to determine
at which stage of disease is the initiation of
treatment superior to natural history.”
Said less eloquently: The ultimate management
decision is WHEN to initiate therapy.
AJO, December 2011
Target Range of IOP
• Set target IOP range when initiating therapy
• General guideline: reduce IOP by the % of the
pretreatment baseline IOP. (Example, if the initial
IOP is 30 mmHg, try to reduce IOP by 30%,
yielding a target IOP of approximately 20 mmHg.)
• Modify target IOP according to the stage and
severity of the disease ( plus 0-20% for severity,
other factors)
• Re-evaluate and adjust over time (years)
• Target IOP ranges
• Low teens (10-13 mmHg)
• Mid teens (14-16 mmHg)
• High teens (17-19 mmHg)
Expert Perspective on “Target IOP”
“Estimation of target pressure is based on a
patient’s risk factors for progression, the level of
IOP that caused damage, the severity of disease,
and longevity. There is, of course, no way to
determine in advance which IOP will be safe. There
is no evidence that setting a variable target has
clinical value for most patients with chronic
glaucoma.”
Reference: Caprioli, J. Archives of Ophthalmology, Aug. 2007
Target Pressure: Use and Abuse
“Despite recent breakthroughs in our knowledge of
risk of progression, we still are making educated
guesses. At all but the highest pressures, not all
patients will progress. Some patients may have
non-pressure dependent optic neuropathies that
are beyond our current understanding and
treatment capabilities. Around half of patients with
normal tension glaucoma will not progress even
without treatment.”
Reference: Werner M. Ophthalmology Web. March 12, 2010.
Predicting Response to Glaucoma Therapy in
One Eye Based on Response in the Fellow Eye
Conclusions: The change in IOP of one eye due to
a medication may be predictive of the subsequent
response of the fellow eye to the same medication
in glaucoma suspects, but not in patients with
POAG.
Using the fellow eye as a control may confer a
more accurate portrayal of the true therapeutic
effects of a medicine although further study is
needed to support both of these findings.
Reference: O Chaudhary et al. Arch of Ophthalmol. September 2008
The Therapeutic Monocular
Trial in Glaucoma
“The most reliable method of assessing drug
effectiveness is by performing a series of pre- and
post-treatment IOP measurements, but in practice
this has obvious resource implications.”
“The monocular trial provides a significantly more
accurate estimate of the therapeutic response
when initiating prostaglandin monotherapy in
untreated eyes. It is particularly helpful in avoiding
overestimation of effectiveness and so reducing
the number of patients on inadequate treatment.”
Oph. November 2011
Contrary View on the Monocular Trial
• Spontaneous IOP variation might mask or mimic
the true drug effect
• IOP change in one eye may not adequately
predict IOP effect in the fellow treated eye
• “There is no useful information about drug
efficacy to be gained by testing only one eye if
both need to be treated.”
• And, just for perspective; “Glaucoma is a chronic
and slowly progressive disease, and most
patients do not require acute IOP reduction.”
Oph. November 2011
Glaucoma Follow-Up
• Most controlled glaucoma patients are seen
every 3 to 4 months for monitoring of the IOP and
ONH status
• Visual Fields and/or a scan are done as
frequently as necessary, and at least once yearly
• A dilated stereoscopic view of the optic nerve
should be performed at least yearly, however, a
quick look should be done at each visit.
• If control is felt inadequate, more aggressive
follow-up is in order until adequate control of the
patient is achieved
Key Excerpts From
Glaucoma Clinical Trials and What They Mean for Our Patients
Paul R Lichter, MD, AJO, July 2003
“Extrapolating the results of clinical trials to everyday practice is a
challenge not only for the average clinician reading the literature, but
also for experts in clinical research.”
“…there is no way for the trial results to indicate whether that
treatment will be effective in a particular patient.”
“In contemplating decisions on whether to treat ocular hypertensive
patients, we should recognize that letting the patients progress (under
careful observation) to frank glaucoma before treating them still will
allow for control of the disease in the vast majority of patients. In
addition, we know that this control can occur well before there is a
threat to interference with activities of daily living.”
“It may be very reasonable to watch for documented progression of
mild visual field loss detected at the initial examination before beginning
treatment. This way, our patients could avoid the unnecessary burden
of nuisance, side effects, and cost associated with a questionable need
for treatment. Conversely, if the field loss is moderate or worse to begin
with or if the patient had high risk for progression, treatment could be
undertaken immediately.”