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Monitoring the Progressing Glaucoma Patient – What Are the Challenges?
Artes et al.
21
investigated the relationship between VF and HRT change
Figure 1: Evaluation of Whom to Treat
3
in a prospective longitudinal study with 84 patients and 41 healthy
controls. At intervals of six months, all participants received SAP, high-
Normal
vision
pass resolution perimetry (single-reversal ‘staircase’ technique) and
HRT. During follow-up, change manifested either predominantly in A
the VF or predominantly in the optic disc. Few patients showed disc B
C
and VF change to the same degree. However, Strouthidis et al.
22
reported on the relationship between a functional map based on
D
interpoint correlations of the VF (HFA) and an anatomical map based
on the distribution of the RNFL in the optic disc. They concluded that
G
there was an association between the strength of correlation
Severe
between test locations in the VF and the relative location of these
functional
impairment
points in corresponding RNFL bundles at the optic disc. These findings
E F
confirm that both imaging and perimetry are required if progression is
not to be missed in patients with OHT or early glaucoma. It is not yet
Blindness
Time of Year Death
clear how best to use these available imaging devices. Unambiguous
diagnosis
answers to questions in terms of which machine is best to use, the
frequency of testing and the interpretation of data cannot yet be
Table 1: Rates of Visual Field Change
3
offered. However, HRT is currently the tool with the longest retro-
compatibility. It is also important to remember that the (developing) Progression Rate (dB year)
imaging techniques are still objective adjuncts and they will never A: Total MD change (dB) 2 years 3 years 5 years
replace a meticulous clinical examination.
-1 -0.5 -0.3 -0.2
-2 -1 -0.7 -0.4
Determining the Rate of Progression
-4 -2 -1.3 -0.8
Rate of Progression Provides Important
Annual Examinations
Information About the Risk of Vision Loss
B: Total MD change (dB) 2 years 3 years 5 years
Not all patients progress at the same rate. Therefore, guidelines
-1 7 6 4
recommend determining rate of progression for the individual patient
-2 5 4 3
when planning management. Line A in
-4 3 3 2
Figure 1 represents the effect
of ageing alone on ganglion cell loss. “The patient identified by line B
Rates corresponding to total change in mean deviation over two, three and five years (A)
and the number of visual fields per year required to detect the corresponding change with
is worsening due to disease, but might not need treatment, while
80% power (B). MD = mean deviation.
those following lines C–G will be disabled within their lifetime unless
successfully treated.”
3
algorithms. The standard strategy for Humphrey automatic perimetry
(HFA) is Swedish interactive threshold algorithm (SITA) standard (±6-
Regular Visual Field Assessment Is Recommended to minute testing time). SITA fast is a shorter strategy (±3-minute testing
Identify the Rate of Progression time) that can be used for screening and follow-up, but is slightly more
Evidence-based guidance on the frequency of VF examinations difficult for the patient. The standard strategy for the Octopus is the
required to identify clinically meaningful rates of change in glaucoma dynamic strategy (±6-minute testing time). Fewer test locations in
appeared only recently.
23 23
Table 1 illustrates that three examinations fewer than four stages (e.g. 32 test locations in two stages) can be
per year are required to identify an overall change in mean deviation used for screening (±3-minute testing time). However, four stages (59
(MD) of 4dB over two years in a patient with average VF variability. test locations) are more appropriate when following up VF damage.
From these results, the recommendation can be deduced to perform Tendency-orientated perimetry (TOP) is another fast algorithm from
three VFs (SAP) per year in the first two years of follow-up. Octopus that can be used for screening purposes.
Subsequently, the rate of VF progression can be assessed. Afterwards,
one VF per year is sufficient, with a control VF if any change is In glaucoma the VF is performed in the central 24º field, in correlation
suspected. “There are many circumstances when the frequency of with the distribution of the majority of retinal ganglion cells. This
examinations should be increased because of a higher perceived risk corresponds to the 24–2 programme for HFA and the G1/G2
of functional loss – for example, suspicion of optic disc change, programme for the Octopus. Compared with the 30º programs (30–2
inadequate IOP control, advanced field damage, pseudo exfoliation, for HFA or 32 for Octopus), there is only a small reduction in
increased age and morbidity in the fellow eye.”
23
It is important to information, but fewer artefacts.
stress that non-conventional perimetry (e.g. frequency doubling
technology and short wavelength automated perimetry) can support Computer-assisted progression determination exists in two modes:
but not replace SAP. it can be event- or trend-based.
3
The event-based mode is designed
to determine whether the VF has progressed compared with
Integration of Visual Fields into baseline (e.g. glaucoma change probability maps [GPA]) These
Clinical Practice programmes require a minimum of five tests to exhibit likely
It is important to use the same strategy (threshold algorithm) for repeat progression.
3
By contrast, the trend-based computer-assisted mode
VF examinations.
3
Both Humphrey and Octopus automatic perimetry is designed to determine rate of progression (e.g. Peridata and
can be performed in the standard or in shorter screening modes. The Progressor for point-wise linear regression analysis, or EyeSuite
classic staircase bracketing strategy has now been replaced by faster and GPA for linear regression analysis of the indices).
24–28
EUROPEAN OPHTHALMIC REVIEW 25
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