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EXTENDED REPORT
25-gauge vs 20-gauge system for pars plana vitrectomy: a
prospective randomised clinical trial
Lukas Kellner, Barbara Wimpissinger, Ulrike Stolba, Werner Brannath, Susanne Binder
...................................................................................................................................
See end of article for
authors’ affiliations
........................
Correspondence to:
Dr S Binder, Department of
Ophthalmology, Ludwig
Boltzmann Institute for
Retinology and
Biomicroscopic Laser
Surgery, Rudolph
Foundation Clinic, Juchgasse
25, 1030 Vienna, Austria;
susanne.binder@wienkav.at
Accepted 8 December 2006
Published Online First
3 January 2007
........................
Br J Ophthalmol 2007;91:945–948. doi: 10.1136/bjo.2006.106799
Aim: To compare 25-gauge vs 20-gauge system for pars plana vitrectomy in a prospective, randomised,
controlled clinical trial.
Methods: Three-port pars plana vitrectomy was performed in 60 patients belonging to 2 groups. Evaluations
were performed preoperatively, intraoperatively, during the first three postoperative days, at 1 week, and at
1 and 3 months. The main outcome measure was time for surgery, divided into duration of wound opening,
vitrectomy, retinal manipulation and wound closure.
Results: The total duration of surgery showed no significant difference between the groups (p =0.67). The 25-
gauge group showed significantly shorter duration of wound opening (p,0.001) and wound closure
(p,0.001). In contrast, the vitrectomy duration was significantly longer in the 25-gauge group (p,0.001).
Conjunctival injection and subjective postoperative pain showed significantly lower irritation in the 25-gauge
group (p,0.001 for both).
Conclusion: The 25-gauge vitrectomy system offered significantly improved patient comfort during the first
postoperative week. The smaller surgical openings facilitated wound healing and minimised pain. Duration of
surgery was comparable between the two systems—the shorter time needed for wound opening and closure
in the 25-gauge group being equalised by the longer vitrectomy duration. Intraoperative as well as retinal
manipulation and illumination caused more surgical difficulties using the 25-gauge system.
Three-port 20-gauge vitrectomy systems have been the gold
standard for vitreous surgery since 1974.
1
During the past
30 years, its instrumentation has successfully been devel-
oped further. The standard system, demanding conjunctival
incisions and sclerotomies of 0.89 mm diameter (20 gauge),
was subsequently made smaller and less traumatic. For
example, a 23-gauge system was developed in the 1980s by
Peyman
2
, and 23-gauge-sized instruments have been mainly
used for paediatric ophthalmic surgery.
In 2002, a 25-gauge system was developed and made
commercially available by Fujii et al.
3
First reports have
emphasised several advantages in the use of the new sutureless
transconjunctival system.
4–6
One advantage was a gain in time
for surgery by avoiding extra efforts to open and close sclera
and conjunctiva separately. This subsequently minimises
surgically induced trauma and foreign body perception other-
wise caused by manipulation and sutures, as well as the
possible reactions related to the suture material itself. This was
supposed to reduce the duration of the convalescence period
and of the postoperative inflammatory response. The micro-
cannulas of the system permit interchangeability of instru-
ments between entry sites and might protect the vitreous base
from mechanical traction.
On the other hand, suction and flow rates in the 25-gauge
system are significantly lower than the comparable parameters
in the established 20-gauge technique, as a result of the smaller
diameter of the 25-gauge system.
7
This could eventually cause
difficulties in removing tight vitreous strands, epiretinal
membranes, or denser haemorrhages or clots. Membranes too
thick or too big in size to be cut inside the eye could lead to
enlargement of the sclerotomy and change of instrument sets.
The time advantage gained by the use of the sutureless
technique could perhaps be lost by the need for a longer
vitrectomy time or longer retinal manipulation time in order to
remove the same amount of vitreous through the smaller
calibre of the instrument, or because of difficulties in grasping
with finer forceps. Although single advantages and disadvan-
tages have been reported in case series, precise evaluation in a
prospective randomised clinical trial is missing.
The aim of this study is to compare the functional and
clinical differences between a 20-gauge surgical system and the
newly developed 25-gauge system for pars plana vitrectomy.
METHODS
A randomised prospective controlled clinical trial was designed,
comparing the two vitrectomy systems in a group of diseases
requiring uncomplicated vitreoretinal surgery. Patients with
vitreoretinal pathology such as preretinal membrane, posterior
uveitis, uncomplicated vitreous haemorrhage, synchisis scintil-
lans, macular oedema or macular hole were included. Cases
requiring silicone oil tamponade or pre-vitrectomised or
retinally preoperated patients were excluded. Only one eye
per patient was included in our study. Surgery was performed
by two experienced randomly surgeons (S.B., U.S.). The
number of subjects to be studied was determined by statistical
pre-study evaluation (by the two-group t –test, with a 0.05 two-
sided significance level). Sixty patients were divided into two
randomised groups, 30 for the 25-gauge system (25 gr) and 30
for the 20-gauge system (20 gr). In all cases, a minimum of 80%
of vitreous was removed. Institutional review board approval
and complete informed patient consent were obtained for all
patients, and all interventions followed standard of care
practices for these vitreoretinal diseases.
The data collected included patient age, sex, the duration of
surgery, divided into duration of wound opening, vitrectomy,
retinal manipulation (in eyes with macular holes, pucker and
oedema) and wound closure. Furthermore, the postoperative
subjective pain, conjunctival injection, eye pressure, visual
acuity, the retinal situation, as well as intraoperative or
postoperative complications were evaluated. In addition, the
Abbreviation: IOP, intraocular pressure
945
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surgeons’ judgements of surgical tools and technical difficulties
were documented.
Examinations were performed the day before surgery, the
first, second and third postoperative days, at 1 week, and at 1
and 3 months after surgery.
Intraoperative time measurement
A stopwatch was used from the beginning of the first cut into
the conjunctiva. Measured criteria used for evaluation were the
time needed for conjunctival and scleral preparation, for
vitrectomy (consisting of the vitrectomy itself and the retinal
manipulation) and for withdrawal of the cannulas, closing and
suturing of sclerotomies and conjunctiva.
Assessment of conjunctiva
The conjunctival injection was measured on a scale ranging
from 0 to 4: (no conjunctival injection), 1 (light), 2 (medium), 3
(high) and 4 (heavy).
Assessment of postoperative recovery
Pain and discomfort were measured using a grading scale from
1 to 4: (no pain), 2 (light), 3 (heavy) and 4 (severe).
Intraocular pressure
Intraocular pressure (IOP) was measured using Goldmann
applanation tonometry.
Visual acuity
Visual distance acuity using the log minimum angle of
resolution charts according to the guidelines of the Treatment
of Age-Related Macular Degeneration with Photodynamic
Therapy study (test distance 4 m, letter-by-letter scoring, chart
luminance 100 cd/m
2
) and visual reading acuity using
standardised, German-language Radner reading charts were
measured using the patient’s optimal refractive correction.
89
Surgical technique
All patients underwent surgery in general anaesthesia. The two
surgical systems used (Oertli Instrumente AG, Berneck,
Switzerland and Alcon Laboratories Inc, Fort Worth, Texas,
USA) were commercially available, with comparable cutting
rates of 1200–1500/min (20–25 Hz). Only the suction rate had
to be higher in the 25 gr (400–500 ml/min vs 150–200 ml/min).
In the 25 gr, the trocars were placed through the conjunctiva
and the sclera by shifting the conjunctiva sidewards. After
vitrectomy, the trocars were removed and the sclerotomies
covered by the conjunctiva.
In the 20 gr, the conjunctiva was opened in a nasal triangle
and in a temporal quadrangle 1 mm from the limbus, and then
the scleral incisions were performed. After vitrectomy, the
sclerotomies and conjunctiva were closed with vicryl 7-0 sutures.
Statistical methods
The treatment groups were compared with respect to the
duration of wound opening, vitrectomy, retinal manipulation,
wound closure, as well as their sum (total duration of surgery).
The sum represents the primary end point of the study. We
further considered the improvement in visual acuity 3 months
postoperatively, IOP at days 1 and 2 after surgery, and
conjunctival injection and postoperative pain, as well as the
area under the curve, documented at baseline, days 1, 2 and 3,
at 1 week, and 1 and 3 months after surgery. For patients who
were unable to read the largest test sentence, the Radner value
was set to 1.5.
As most end points exhibit strongly skewed distributions
with heavy ties, the treatment groups were compared using the
exact Wilcoxon’s rank sum test. The improvement in distance
Table 1 Summary of qualitative baseline values
20 gauge 25 gauge
p Value of Fisher’s
exact test
Sex 0.18
Women 16 (53.3) 22 (73.3)
Men 14 (46.7) 8 (26.7)
Diagnosis 0.71
Macular hole 15 (50) 11 (36.7)
Preretinal membrane 14 (46.7) 18 (60)
Synchisis scintillans 1 (3.3) 1 (3.3)
Combined cataract surgery 1
No 8 (26.7) 9 (30)
Yes 22 (73.3) 21 (70)
Eye 0.44
Left 13 (43.3) 17 (56.7)
Right 17 (56.7) 13 (43.3)
Values are given as n (%).
Table 2 Summary of quantitative baseline values for each treatment group
20 gauge 25 gauge p Value of
Wilcoxon’s
testMin 1.Q*Mean (SD) Median 3.QMax Min 1.Q Mean (SD) Median 3.Q Max
Visual acuity (ETDRS) 0.04 0.33 0.48 (0.23) 0.51 0.62 0.86 0.20 0.37 0.50 (0.18) 0.47 0.62 0.88 0.54
Reading acuity (Radner) 0.20 0.50 0.60 (0.20) 0.60 0.70 1.00 0.10 0.30 0.52 (0.24) 0.55 0.70 1.10 0.94
Eye pressure (mm Hg) 10.0 12.0 14.4 (2.50) 14.5 16.0 20.0 8.00 12.5 14.7 (3.30) 15.0 16.0 22.0 0.69
ETDRS, Early Treatment Diabetic Retinopathy Study; Max, maximum; Min, minimum.
*First quartile, mean.
Third quartile, mean.
946 Kellner, Wimpissinger, Stolba, et al
www.bjophthalmol.com
and reading visual acuity 3 months after surgery was investi-
gated by exact one-sample Wilcoxon’s tests.
RESULTS
The treatment groups were compared with respect to the
baseline measurements (tables 1 and 2). No significant
differences were found for the baseline values.
Regarding the duration of surgery, we observed that the 25 gr
showed a significantly shorter duration of wound opening
(p,0.001) as well as wound closing (p,0.001) compared with
the 20 gr. By contrast, vitrectomy duration was significantly
longer in the 25 gr compared with the 20 gr (p,0.001). There
was no significant difference between the two groups regarding
the duration of retinal manipulation. Finally, the total duration
of surgery did not show significant difference between the two
groups (p = 0.67). These results are presented in table 3.
The visual distance and reading acuity changes from baseline
until 3 months after surgery were also similar in both groups. A
significant increase in distance visual acuity (20 gr: p = 0.02; 25
gr: p,0.001) and a significant improvement in reading acuity
(20 gr: p = 0.01; 25 gr: p = 0.003) were observed in both groups
3 months after surgery.
During the first two postoperative days, the 25 gr showed
more eyes with low pressure (,10 mm Hg), but no severe
hypotonies (,6 mm Hg) were observed. During days 1–2, the
IOP dropped below 10 mm Hg in nine patients of the 25 gr and
in two patients of the 20 gr (Fisher’s exact test p = 0.04). The
maximum difference in IOP from baseline at days 1 and 2 was
significantly smaller in the 25 gr than in the 20 gr (day 1;
p = 0.011; day 2: p = 0.003). During the first 2 days after
surgery, IOP was .20 mm Hg for two patients in both
treatment groups. After 3 days, IOP levels no longer differed
significantly.
Conjunctival injection as well as subjective postoperative
pain showed significantly lower irritation in the 25 gr (p,0.001
for both) compared with the 20 gr.
Both groups showed no significant difference regarding the
amount of vitreous removed (p = 0.24), the amount of applied
gas tamponade (p = 0.24), as well as the area under the gas %
time curve measured at days 1, 2, 3 and at 1 week after surgery.
In 11 of 30 (37%) patients of the 25 gr, one or more technical
difficulties occurred during surgery: in seven cases the vitreous
cutter and the endoinstruments were insufficient to dissect
tight vitreous or epiretinal membranes. In four cases the light
source was inadequate to provide sufficient illumination. Two
cases showed blockage of instruments in the trocar system, and
the trocars had to be replaced. In three cases suction was too
weak to remove blood effectively from inside the eye.
Membrane peeling and rotation of the globe were hindered
by the increased flexibility of the 25 g endoinstruments in three
cases. Five cases, for the sake of patients’ security, required an
intraoperative switch to the 20-gauge system; in two cases the
switch of instruments affected only the light source. No
postoperative complications occurred in the 25 gr.
In the 20 gr, bad visualisation was described in 1 of 30 (3%)
eyes, but did not affect proper surgical progression.
In two cases, vitreous haemorrhages occurred on the first
postoperative day after 1 month, both cleared without surgical
intervention. Retinal detachment developed in 2 (6.7%) cases,
which could be cured only by a second vitrectomy. One of these
cases showed multiple inferior breaks on the second post-
operative day, whereas the other presented a macular hole
retinal detachment without any peripheral break 4 months
after surgery.
DISCUSSION
In 2002, Fujii et al
3
introduced a 25-gauge system for
transconjunctival sutureless vitrectomy. Their initial experi-
ences were summarised in a retrospective review of 35 cases,
postulating an overall safety of the new system and faster
patient recuperation. However, no objective inflammation
grading scale was used, and the patients were observed only
for 1 day. In a following comparative interventional study, the
same authors showed a significantly reduced operating dura-
tion using the new 25-gauge system.
4
We did not test this
particular system in our study. However, the results are in
contrast with our findings. A possible explanation could be that
in several cases (ie, sheatotomy, epiretinal membrane peeling)
no vitrectomy was performed before or after retinal manipula-
tion when using the 25-gauge system, and no detailed
information was given about the amount of vitreous removed.
Since then, several authors have published their initial and
further experiences with the new system: Ibarra et al
5
retro-
spectively studied 45 consecutive patients and found no
intraoperative complications, no postoperative hypotonies and
no necessity to convert to the 20-gauge system, but post-
operatively found 1 (2.2%) case of inferior retinal detachment,
1 (2.2%) case of macular hole and 79.3% (23 of 29 phakic eyes)
of cases with worsening of cataracts. The small and more
flexible instruments did not allow the surgeon to move the eye
sufficiently, and lower posterior segment illumination caused
difficulties. The authors found that less peripheral vitreous
removed possibly caused anterior vitreoretinal traction and
retinal tears or detachment.
In a non-randomised study, Rizzo et al
6
compared 46 patients
(26 (25 gauge group) vs 20 (20 gauge group)) reporting no
surgery-related complications, with postoperative pain signifi-
cantly lower in the 25-gauge group, but with pain level assessed
only 1 week after surgery. No postoperative hypotony was
observed, the mean duration of surgery was significantly
shorter in the 25-gauge group. Only a core vitrectomy was
performed, and the amount of vitreous removed was not
documented. The postoperative inflammatory score at the
follow-ups showed significantly lower inflammation in the
25-gauge group. This is consistent with our findings. In their
study, preoperative visual acuity was significantly better in the
20 gr. At 1 month, the improvement in visual acuity was
significantly higher in the 25 gr, but after 6 months no
difference in visual acuity could be found. In our study, the
Table 3 Summary of surgery time values and p values of the Wilcoxon’s rank sum tests for
group comparison
Time (s) 20 gauge 25 gauge p Value (Wilcoxon’s test)
Opening time 306 (143) 173 (80) 0.001
Vitrectomy time 490 (239) 774 (328) ,0.001
Retinal manipulation time 378 (283) 504 (366) 0.18
Closing time 357 (83) 112 (153) ,0.001
Total surgery time 1530 (499) 1564 (626) 0.67
Values are mean (SD).
25-gauge vs 20-gauge system for pars plana vitrectomy 947
www.bjophthalmol.com
preoperative as well as the postoperative visual acuities were
comparable in both groups.
Description of postoperative hypotony by several
authors
Lakhanpal et al
10
published 140 consecutive cases of 25 g
vitreoretinal surgery, and found suturing of transconjunctival
sclerotomies necessary in up to 7.1%, because of bleb formation.
Neither intraoperative complications nor conversion to the 20-
gauge system was reported; the IOP was stable and no retinal
detachment occurred.
In a retrospective study of 41 eyes, Yoon et al
11
saw transient
hypotony of 4 mm Hg in one eye. A further retrospective study
of 71 eyes by Yanyali et al
12
showed hypotony between 6 and
10 mm Hg in 16.9% of the eyes on the first postoperative day,
but normalisation within 1 week. Liu et al
13
published a case
report regarding a patient with a 360˚choroidal detachment on
the first postoperative day, suspected to be postoperative
hypotony. So far only one case of endophthalmitis after 25-
gauge vitrectomy has been reported.
14
In a randomised prospective study of 30 patients, Chang et al
15
measured time for combined surgery, comparing 20-gaugevs 25-
gauge systems only for preparation and closure of sclerotomies,
neglecting conjunctival opening and closing and measuring the
time for phacoemulsification and that for pars plana vitrectomy
together, leaving the time distribution unclear. No objective
staging of ocular redness was performed and not all 25-gauge
instruments were available. Oshima et al
16
performed a retro-
spective review of 150 eyes having previously undergone 25-
gauge vitrectomy, phacoemulsification and intraocular lens
implantation, observing postoperative transient hypotony in
13% (18 eyes) of cases 1 week after surgery, 1 (0.67%) case of
retinal detachment, but no case of endophthalmitis.
In our randomised prospective controlled clinical study, we
found 25-gauge vitrectomy to be a safe and effective system for
the management of a variety of uncomplicated vitreoretinal
diseases, especially those cases requiring lesser intraocular
manipulations. However, setting of the trocars requires a
learning curve, and the higher flexibility of the instruments
hinders management of tight membranes. The 25-gauge system
offers significantly higher patient comfort during the first
postoperative week, and the risk of postoperative severe
complications such as retinal detachment and vitreous hae-
morrhage seems to be lower. This could be related to the fact
that trocars were used in the 25-gauge cases, and also to the
smaller incisions. In our study, 80% of the vitreous was
removed in all cases and great care was taken to remove the
posterior hyaloid in every case, whereas only core vitrectomy of
unknown amount was done in the other studies. We believe
that, for this reason, the total duration of surgery showed no
difference between the two groups. The important factor that
emerged was a clearly higher patient comfort with the 25-gauge
system. This is in accordance with many other studies.
356
Whether a higher percentage of postoperative hypotonies that
we and others observed might lead to a higher rate of
endophthalmitis needs to be investigated further.
14
Although
the learning curve for the 25-gauge sutureless vitrectomy must
be considered, higher flexibility and lesser mechanical stability
can lead to a limitation of surgical indications and increased
costs when an additional 20-gauge vitreous surgery system has
to be provided. Further study as well as technical development
will be needed to improve the principle of sutureless transcon-
junctival pars plana vitrectomy and to minimise intraoperative
handicaps as well as potential postoperative risks.
Authors’ affiliations
.......................
Lukas Kellner, Barbara Wimpissinger, Ulrike Stolba, Susanne Binder,
Department of Ophthalmology, Rudolph Foundation Clinic, Vienna,
Austria; Ludwig Boltzmann Institute for Retinology and Biomicroscopic
Laser Surgery, Rudolph Foundation Clinic, Vienna, Austria
Werner Brannath, Section of Medical Statistics, Medical University of
Vienna, Vienna, Austria
Competing interests: None.
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