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1Multi-spot laser coagulation with the VISULAS 532s VITE :A
comparative study of 101 proceduresA mono-center clinical study to
compare treatment workflow and patient compliance of multi-spot
coagulation with the new VISULAS 532s VITE laser in comparison to
single-spot laser therapy with the conventional green coagulation
laser VISULAS 532s
Antje Rckl, MD, Marcus Blum, MD, Department of Ophthalmology,
Helios Kliniken Erfurt, Germany
ABSTRACT
BACKGROUND
VISULAS 532s VITE is a 532 nm photocoagulation la-ser which is
able to operate both in classic single-spot treatment modes as well
as in a new, semi-automated multi-spot treatment mode. In the
latter mode, the laser fires a predetermined linear spot sequence
at high speed, released with the joystick trigger button of the
laser slit lamp. The authors report their early experience with the
system and compared the new multi-spot with the con-ventional
single-spot functionality.
METHODS
101 procedures of pan-retinal photocoagulation (PRP) have been
divided into two groups - group A: laser therapy in classic
single-spot coagulation with the con-ventional VISULAS 532s, and
group B: laser therapy in multi-spot operation using the new
functionality of the VISULAS 532s VITE. The shorter pulse duration
of 20 ms in multi-spot group B in comparison with 100-150 ms in
single-spot group A, has been compensated for by high-er laser
power values in order to achieve a comparable, moderate blanching
of the retina.
RESULTS
Compared with the single-spot treatment group, mul-ti-spot
coagulation with the VISULAS 532s VITE saves half a minute per 100
applied laser shots in an average PRP session.
Depending on the number of laser spots per multi-spot sequence,
up to 2/3 of the overall treatment time of an average PRP session
can be saved. Whereas 46.0% of patients of single-spot group A have
reported feeling some degree of pain during la-ser treatment, only
1.3% of the patients in multi-spot group B have reported feeling
pain during their treat-ment.The average pain value in the
single-spot coagulation group A was 2.1. In the multi-spot
coagulation group B, the average pain value was only 0.1.No adverse
events were noted in either of the two groups.
INTRODUCTION
Laser photocoagulation remains the gold standard in the therapy
of many retinal vascular disorders.For more than 30 years, it has
been known that panretinal laser photocoagulation (PRP) is
effective in treating proliferative retinopathy in a wide variety
of underlying conditions, of which diabetic retinopathy is the most
common indication. The most frequently used photocoagulation
settings are still based on the original recommendations of the DRS
study from the late seventies /1/. Classic photocoagula-tion
conditions of pulse widths from 100 to 200 ms and laser powers from
200 to 400 mW are still widely recom-mended although commercially
available photocoagula-tion lasers have been capable of delivering
both shorter
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2pulse widths as well as higher laser power for years. For
instance, the VISULAS 532s from Carl Zeiss delivers laser pulses
with pulse durations from 10 ms to continuous wave, offering a
maximum laser power of 1.5 W (mea-sured at the cornea). Recently,
Zeiss has implemented the concept of fast and flexible multi-spot
cascades in the new VITE option of the VISULAS 532s
photocoagulation laser. The purpose of this study was to compare
the new multi-spot to the tra-ditional single-spot operation of the
VISULAS 532s VITE. One goal was to investigate if and how the
improved VITE functionality accelerates photocoagulation work-flow
in daily clinical practice in comparison to classic single-spot
use. The second goal was to evaluate if and how patient compliance
is influenced by the change in the modus operandi.
METHODS
PATIENTS
Only patients whose diagnosis definitely requires a pan-retinal
photocoagulation therapy have been recruited for this study. No
restrictions regarding the patients race or gender have been
postulated. Only patients aged 18 years or older participated in
this study. Patients with ocular pathologies such as tremor,
cataract, cloudy vitre-ous or acute inflammation have been excluded
from this study. Also patients who received a laser treatment with
less than 350 burns were retroactively excluded from the study. All
patients were treated from June 2009 to Octo-ber 2009.
Of the group A procedures of the single-spot group, 28 (80%)
were for Proliferative Diabetic Retinopathy, 4 (11%) for Central
Retinal Artery Occlusion, and 3 (9%) for Central Retinal Vein
Occlusion. 7 (20%) of group A treatments were initial first
treatments, and 28 (80%) re-treatments (including a second and
third PRP session and re-filling procedures).
Of the group B procedures of the multi-spot group, 50 (75%) were
for Proliferative Diabetic Retinopathy, 7 (11%) for Central Retinal
Artery Occlusion, and 9 (14%) for Central Retinal Vein Occlusion.
15 (23%) of group B treatments were initial first treatments, and
51 (77%) re-treatments (including both a second / third PRP session
and re-filling procedures).
Group A (non-VITE)Single-spot
[100 150 ms]
Group B (VITE)
Multi-spot [20 ms]
Number of Procedures 35 66
Patient Gender Female Male
49% [17]51% [18]
33% [22]67% [44]
Patient AgeMean valueStandard DeviationRange
6312
37 90
6411
38 88
Diagnosis Diabetic Retinopathy Central Retinal Artery
OcclusionCentral Retinal Vein Occlusion
80% [28]
11% [4]
9% [3]
76% [50]
14% [9]
10% [7]
Laser Therapy First treatment Re-treatment
20% [7]80% [28]
23% [15]77% [51]
Table 1: Patient demographics
TREATMENT REGIMEN
The VISULAS 532s VITE is a frequency-doubled, neodym-ium-doped
yttrium aluminum garnet (Nd:YAG) solid-state laser operating at 532
nm wavelength. Besides the clas-sical single-spot treatment mode,
the VISULAS 532s VITE is capable of delivering multi-spot sequences
at a single press of the release button on the slit lamp joystick.
Based on the concept of flexible treatment multi-spot cascades,
linear, circular or customized coagulation strategies can be
pursued (see Fig. 1). Linear spot sequences of variable orientation
consisting of 3 to 8 single laser spots are most suitable for
pan-retinal photocoagulation. Semi-automated parallel movement of
the slit lamp field and the laser beam in the multi-spot mode
allows indi-vidual application of several spots consecutively in
fast linear sequences to fill in a large retinal area.During the
normal retina consultation hours in the Helios Kliniken Erfurt, all
patients were randomly allocated to receive either laser treatment
in regimen A or B. In both treatment regimens, a single quadrant of
the retina was treated with about 500 peripheral laser spots. In
group A, shots of scatter laser photocoagulation using
con-ventional laser parameters in the single-spot operation mode
were applied: a spot size of 200 m, exposure times between 100 and
150 ms, and laser power values sufficient to cause moderate
blanching of the retina were used. In group B, laser treatment was
also performed
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3with 200 m spot size, but this time in multi-spot opera-tion
with a pulse duration of 20 ms. Therefore, higher laser power
values had to be used in order to provide a similar visible laser
effect in both study groups. For the VITE group B we used straight,
linear spot sequences of variable orientation. We decided to use 3
to 6 individual laser spots per sequence with a spacing of a single
spot diameter.
Group A Non-VITE treatmentSingle-spot
[100 150 ms]
Group BVITE
treatmentMulti-spot
[20 ms]
Laser spot diameter [m]
200 200
Laser power [mW]Mean valueStandard deviationRange
15688
70380
280105
120600
Pulse duration [ms]Mean valueStandard deviationRange
11622
100 150
20020
Number of laser burns Mean valueStandard deviationRange
50965
462 609
55582
400 837
Table 2: Treatment parameters
The treatment of all patients was recorded on video in order to
compare treatment times with the two treat-
ment regimens. The video camera, which was placed on a
co-observation tube, was switched on when the pa-tient took a seat,
and switched off when the patient left from the chair after
treatment. The treatment time was defined as the time from the
first to the last applied laser pulse in a treatment session. It
was measured after treat-ment on the basis of the acquired video
data. Fundus im-ages were acquired after laser treatment with an
FF450 fundus camera from Carl Zeiss in order to compare treat-ment
regimens regarding the spatial regularity, homoge-neity and
intensity of the applied laser spots.
At the end of the laser treatment, patients were asked to mark
on a visual analog, linear scale the severity of the pain
experienced for the two treatment regimens with 0 (= no pain) to 10
(= most severe pain ever experienced). The results were presented
in terms of mean pain scores and analyzed in terms of standard
deviations.
RESULTS and DISCUSSION
In the study period, 142 procedures were included. Finally, a
complete set of data was available from 101 procedures after
exclusion criteria. 35 of them were ap-plied in the single-spot
treatment mode (= Group A, non-VITE group), and 66 in the
multi-spot treatment mode (= Group B, VITE group).
The average laser pulse of the 35 conventional treat-ments in
the single-spot treatment mode (= Group A,
Fig. 1: Possible, multi-spot treatment strategies with the
VISULAS 532s VITE
Colour fundus image of a multi-spot laser treatment with
linear cascades of the VISULAS 532s VITE
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4non-VITE group) had a duration of 116 ms and a laser power of
157 mW. The average non-VITE treatment consisted of 512 laser
burns. The average laser pulse of the 66 treatments in the
multi-spot treatment mode (= Group B, VITE group) had a duration of
20 ms and a laser power of 290 mW. The average VITE treatment
consisted of 555 laser burns.
200
250
300
350
r Pow
er [m
W]
0
50
100
150
0 20 40 60 80 100 120 140 160
Aver
age
Lase
r
Pulse Duration [ms]
Fig. 2: Average laser power values used depending on laser
pulse duration
Fig. 2 displays the average values of the mean laser power
values for all applied pulse durations. The applied laser power
values in the multi-spot treatment group B had been chosen in such
a way that the visible clinical endpoint (the burns) in this group
corresponds to the clinical outcomes in group A. Fig. 2 illustrates
that shorter laser pulse durations have to be compensated for with
higher laser power values. Because of the relatively gen-tle laser
powers we used in our single-spot therapy regi-men, this
compensation for the shorter 20 ms multi-spot pulses did not cause
any clinical side-effects at all.It should be noted that physicians
who already coagulate with higher laser powers in conventional
treatment may also use 30, 40, or 50 ms pulse durations with the
multi-spot option VITE, which require less compensation in the
applied laser power. We extracted the individual treatment times
from the recorded videos of all laser treatments. Based on the
individual treatment times we calculated a normalized treatment
time value which represents the individual treatment time
normalized to the application of 100 la-ser pulses.
Group A (non-VITE group)
Group B(VITE group)
Number of procedures 35 66
Treatment time (normalized to 100 burns)
Mean valueStandard deviationRange
73.4 sec
9.6 sec61.6 103.7 sec
49.4 sec
14 sec24.0 97.5 sec
Mann Whitney U-Test P < 0.05
Table 3: Normalized treatment time statistics in both study
groups
Comparing the normalized treatment times in the two study
groups, a treatment with 100 laser shots in single-spot treatment
group A takes an average of 73.4 sec-onds, a treatment with 100
laser shots in multi-spot treatment group B takes 49.4 seconds on
average. This corresponds to a time saving of 24.0 seconds per 100
ap-plied laser shots or a relative time saving of 33% in the
multi-spot VITE group B.In order to take into account an initial
learning curve when the operator has to become accustomed to the
system and gain experience with the new multi-spot sequences, we
divided the VITE group B into two subgroups:
Group B1 contains all multi-spot treatments within the first 8
weeks after installation of the system (June and July 2009). Group
B2 contains all multi-spot treatments after week 8 from
installation of the same operator (September and October 2009).
Group B1 (VITE group 8 weeks)
Number of procedures 29 37
Treatment time (normalized to 100 burns)
Mean valueStandard deviationRange
55.5 sec
17.0 sec24.0 97.5 sec
44.8 sec
9.9 sec27.2 62.3 sec
Mann Whitney U-Test P < 0.05
Table 4: Normalized treatment time statistics in both B sub-
groups
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5Comparing the normalized treatment times between the two B
sub-groups, a treatment with 100 laser shots with-in the adoption
phase of 8 weeks takes 55.5 seconds on average; after an adoption
phase it shortens to an aver-age of 44.8 seconds. In other words:
on average, a skilled operator of group B2 saves half a minute per
100 applied laser shots with the multi-spot option VITE compared to
a skilled single-spot treatment operator. This corresponds to a
relative time saving of 40%. Comparing the stan-dard deviation
values of the normalized treatment times of groups A, B1 and B2
from tables 3 and 4, these values suggest that after the adoption
phase of 8 weeks (with a treatment of approximately 50 eyes), the
operator in multi-spot group B2 has gained a similar skill level as
in single-spot reference group A based on several years of
experience with the VISULAS 532s laser.The normalized treatment
time values for all the treat-
ments within this clinical study are displayed in Fig. 3. The
shortest normalized treatment times of about 25 seconds per 100
shots were reached in both B sub-groups. The longest normalized
treatment time of about 95 seconds in group B1 was significantly
reduced to about 60 sec-onds in group B2 after the adoption phase
of 8 weeks. Therefore, the linear interpolation curve of the
normal-ized treatment values of groups B2 shows an identical slope
to the line of single-spot group A, visualizing simi-lar skill
levels of the operator in both groups. Both the faster individual
treatments (left-hand side of the graph) and the slower individual
treatments (right-hand side of the graph) of multi-spot treatment
group B2 show the same time saving of half a minute in comparison
with a comparable treatment procedure in single-spot treat-ment
group A.
60
80
100
120
t tim
e fo
r 100
lase
r sho
ts
0
20
40
0 5 10 15 20 25 30 35 40
Nor
mal
ized
trea
tmen
t
Patient Number
Group A (skilled) Group B1 (< 8w) Group B2 (> 8w)
Linear (Group A (skilled)) Linear (Group B1 (< 8w)) Linear
(Group B2 (> 8w))
Fig. 3: Comparison of the normalized treatment times of groups
A, B1 and B2
Generally, initial PRP sessions on patients with good
com-pliance take the shortest normalized treatment times, whereas
re-filling procedures and patients with weak compliance slow down
the PRP treatment workflow. When working with the multi-spot option
VITE, even the most demanding treatments have a comparable or
short-
er normalized treatment time than the fastest single-spot
therapy outcomes. The therapy workflow can be flexibly adjusted to
the individual patient case by variation of the spot sequence
length. Table 5 shows the statistics of spot sequence lengths used
within the treatment group B2:
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6Number of laser spots per spot-sequence
Patients
3 only 3 % [1]
3 and 4 3 % [1]
4 only 11 % [4]
4 and 5 8 % [3]
5 only 53 % [20]
5 and 6 3 % [1]
6 only 8 % [3]
More than 2 changes between 3, 4, 5, 6 spots (mostly
re-filling)
11 % [4]
Table 5: Statistics of applied multi-spot sequences in Group
B
after 8 weeks
Based on these statistics, Fig. 4 shows the dependency of the
normalized treatment time from the length of the applied
spot-sequence. In this figure, we have considered treatments with a
single sequence length value as well as treatments where we
switched between two length val-ues. Preferably, we treated with 5
spots per sequence in order to have a similar confidence level and
control as we did in the past with single-spot laser treatment.
Sequen-ces of 2 spots only provide minor workflow acceleration.
Large sequences of 7 or 8 spots could be beneficial for initial PRP
treatments. In our study, however, we stayed with our very
controlled way of operation, which makes it more comfortable and
easy both for the operator as well as for the patient. The linear
interpolation curve of Fig. 4 shows a clear trend: The larger the
spot sequence length, the shorter the normalized treatment time.
Treat-ments which alternated between two spot sequence lengths
required slightly longer normalized treatment times because of the
need to switch between the dif-ferent spot sequence length values.
Therefore, they are generally situated above the interpolation
line. Although not experimentally proven in this study, an
extrapolation of the linear regression line to the largest
available spot sequence length value of 8 spots suggest that it may
be possible to shorten the normalized treat-ment time to an average
of 20 to 25 seconds per 100 applied laser spots.
40
50
60
70
80
aliz
ed tr
eatm
ent t
ime
00 la
ser s
hots
0
10
20
30
40
1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0
Aver
age
norm
per 1
0
Laser spots per spot sequence
Fig. 4: Dependency of average normalized treatment time from
the length of a multi-spot sequence
Pain response during laser photocoagulation is variable among
patients and also depends on the treated area on the retina.
However, discomfort remains an impor-tant cause of unsatisfactory
treatment sessions for both patient and physician. Strategies to
make the treatment more comfortable include changing of the laser
param-eters. The results of a small study in the 1990s showed that
patients found shorter exposure, higher power laser treatment much
more comfortable than conventional settings with no apparent
reduction in visible endpoint. A more recent study on 20 patients
has clearly proven that reducing the exposure time and increasing
the laser power reduced pain significantly without compromising the
long-term results of the laser therapy /3/. Shorter du-ration laser
burns may be less painful due to the thermal conduction effects in
the treated tissue. Short-duration burns cool off more rapidly in
comparison with the longer duration burns, in which adjacent
tissues become heated and the energy reaches the pain-sensitive
region in the deeper retinal and choroidal layers.When applying
multi-spot sequences either by the press of the laser slit lamp
joystick or the footswitch pedal, the overall treatment time of a
sequence should not signifi-cantly exceed half a second in order to
avoid interference with eye movements of the patients. Therefore,
when using multi-spot sequences with the VISULAS 532s VITE, the
pulse duration of the individual laser pulses within a sequence is
limited to 2050 ms. In our clinical study, we used significantly
shorter pulse durations in multi-spot group B than in single-spot
group A, which had to be compensated for by laser power (see Table
1).
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7In order to investigate the pain perception connected with the
different laser treatment regimens in both groups, we defined a
graphical linear scale on which we defined de-grees of perceived
pain from 0 (= no pain) to 10 (= severe pain). Patients were shown
this scale right after the laser treatment and asked to score the
perceived pain value. 16 (46.0%) out of the 35 patients of group A
scored a value greater than zero, which indicated some degree of
pain during the laser treatment. The statistics of the pain
response of the single-spot treatment group A is shown in figure
5.2 (1.3%) of the 66 patients of group B reported pain after
treatment with the multi-spot option VITE, with one scoring a value
of 3 and one a value of 4. All other pa-tients of group B had no
pain at all during the multi-spot treatment.
12
14
16
18
20
atie
nts
0
2
4
6
8
10
0 1 2 3 4 5 6 7 8 9 10
Num
ber o
f pa
Pain score
Fig. 5: Pain score statistics of single-spot treatment group
A
The results confirm the findings in /3/ that reducing the
exposure time and increasing the laser power can reduce pain
significantly without compromising the long-term results of the
treatment. Due to the shorter pulse du-ration, there is a reduced
thermal diffusion to adjacent retinal and choroidal layers which
prevents a heating of the pain-sensitive areas.
CONCLUSION
In this study, we treated 35 patients in single-spot treat-ment
with the VISULAS 532s and 66 patients with the new multi-spot
option of the VISULAS 532s VITE.Compared to conventional
single-spot photocoagulation, laser treatment with the VISULAS 532s
VITE significantly reduces the overall treatment time while shorter
pulse durations improve patients pain perception. Our results
suggest that after a learning phase of 8 weeks with a VITE
multi-spot treatment of approximately 50 eyes, an operator can gain
the same degree of routine as a skilled single-spot user with more
than 4 years of experience.Compared with the single-spot treatment
group, multi-spot coagulation with the VISULAS 532s VITE saves half
a minute per 100 applied laser shots in an average PRP ses-sion.
Depending on the number of laser spots per multi-spot sequence, up
to 2/3 of the overall treatment time of an average PRP session can
be saved. Although rapid laser treatment with multi-spot cascades
requires short individual pulse durations, which have to be
compensated for with higher laser power, no adverse side-effects
have been observed during the multi-spot treatment sessions with
the VISULAS 532s VITE. On the contrary, only 2 patients (1.3%)
treated with the VISULAS 532s VITE in the multi-spot group reported
feel-ing pain, whereas 16 patients (46.0%) patients treated in the
conventional way reported feeling pain during the laser
treatment.
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8Carl Zeiss Meditec AG
Goeschwitzer Str. 5152
07745 Jena
GERMANY
Phone: +49 3641 220 333
Fax: +49 3641 220 112
[email protected]
www.meditec.zeiss.com
Publ
icat
ion
No:
000
000-
1839
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REFERENCES
/1/ The Diabetic Retinopathy Study Research Group:
Photocoagulation treatment of proliferative diabetic retinopathy:
The second report from the Diabetic Reti-nopathy Study. Arch
Ophthalmol 1978; 85: 81106.
/2/ Friberg et al.: Alteration of pulse configuration af-fects
the pain response during diode laser, Lasers Surg Med 16, 1995,
380-383.
/3/ Al-Hussainy et al.: Pain response and follow-up of patients
undergoing pan-retinal laser photocoagulation with reduced exposure
times, Eye 22, 2008, 96-99.
