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NR 7-9/2008
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Transitory hypotony
as a prognostic factor in combined procedures of
phacoemulsification and deep sclerectomy
Przejściowa hypotonia jako
czynnik prognostyczny po operacji sklerektomii głebokiej
łączonej z fakoemulsyfikacją
Marek Rękas, Anna Siemiątkowska, Andrzej
Stankiewicz
Department of Ophthalmology, Military Health Service Institute
in Warsaw
Head: Prof. Andrzej Stankiewicz, MD, PhD |
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| Summary: |
Purpose: To determinate
the influence of hypotonia on the effectiveness of
phacoemulsification and deep sclerectomy performed
simultanously with the SK-gel implant in 15 months
follow up.
Material and methods: The retrospective analysis
comprised group I (IOP ≤ 6 mm Hg) – 50 eyes and group II
(IOP > 6 mm Hg) – 75 eyes. Uncontrolled primary
open-angle glaucoma and coexisting cataract were the
indication. DBCVA, IOP, anterior segment and eye fundus
were assessed as well as the number of antiglaucoma
medications. The patients were examined on the first and
the seventh day as well as at 1, 3, 6, 12 and 15 months.
IOP ≤ 12.15 and 18 mm Hg was accepted as surgical
success criterion. T - Student test was used in
statistical analysis and variance was analysed. The
survival analysis was worked out with Kaplan-Meier
method.
Results: After 15 months the decrease of mean IOP was
obtained in group I by 35.9% (p< 0.05) and in group II
by 33.5% (p< 0.05). There were no statistical
differences between the number of the applied
antiglaucoma medications in the investigated groups.
Finally, a qualified surgical success was obtained for
the criterion ≤ 18 mmHg in 97.7% of cases in group I and
in 87.9% in group II (p= 0.013). For the criterion ≤ 15
mm Hg – in group I 84.3% and in group II 66.4% (p<
0.001), whereas for the criterion ≤ 12 mm Hg
respectively in group I 41.2% and in group II 39.3% (p =
0.015). DCBVA 15 months after the surgery was 0.84 ±
0.24 in group I and 0.71 ± 0.25 in group II. At the end
of the follow up no significant differences of DBCVA
were found between the investigated groups (p> 0.05).
Conclusions: Hypotonia is an important positive
prognostic factor in the first 24 h after surgery in the
case of phacoemulsification, performed at the same time
with deep sclerectomy. |
| Słowa kluczowe: |
hypotonia, sklerektomia
głęboka, SK-gel implant. |
| Key words: |
hypotonia, deep
sclerectomy, SK-gel implant. |
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Introduction
The fibrosis in postoperative period is a limitation in
penetrated procedures applied in current glaucoma surgery (1,2).
This process can limit to a lesser extent the results of
non-penetrating surgeries because subconjunctival route is one
of four routes of aqueous humour outflow (3). However, it should
be emphasized that the presence of a flat filtering bleb also in
this case is a favourable prognostic symptom (4). In the initial
postoperative period deep sclerectomy functions similarly to
classic trabeculectomy through subconjunctival route and only
then transcleral, suprachoroid and Schlemm’s canal routes are
activated (3). Thus, the filtering membrane TDM (trabeculo-Descemet’s
membrane), containing Descemet’s membrane and Schlemm’s canal
devoid during surgery of the external wall, is the main barrier
between the anterior chamber and subconjunctival space.
Particularly that the scleral flap contrary to trabeculectomy is
not a marked counterbalance for this outflow in the case of
non-penetrating procedures due to decompressive space formed in
the sclera.
Non-penetrating deep sclerectomy is technically a difficult
surgical procedure and thus it does not find many supporters
among glaucoma surgeons. The most difficult technically moment
of the surgery is identification of Schlemm’s canal and its
deroofing as well as separation of the Descemet’s membrane from
the sclera (5). Cicatricial changes resulting either from the
nature of the pathological process or from iatrogenic effect of
previous procedures such as trabeculoplasty, goniopuncture or
prolonged pharmacotherapy can be the cause of technical problems
and in consequence of intraoperative complications (6). And in
this aspect, to achieve good follow up results the above remarks
should be taken into account in the qualification for surgery.
Hypotony in the initial postoperative period may be the
reflection of the surgical technique particularly of the
correctness of TDM dissection. Thus, it is justified to verify
its effect on the outcome of non-penetrating surgeries combined
with phacoemulsification which has become the aim of this study.
Material and methods
125 eyes of 111 patients with medically uncontrolled primary
open angle glaucoma were subjected to prospective analysis. All
these patients were treated at the Military Health Service
Institute in Warsaw. There were 59 women and 52 men, mean age
73.4 ± 7.5 years. Each patient underwent phacoemulsification and
deep sclerectomy at the same time with SK-gel implant. Open
angle glaucoma treated with at least two antiglaucoma drugs,
without satisfying IOP control or progression of defects in
visual field and coexisting cataract, were the indications for
surgery.
In the first stage non-penetrating deep sclerectomy was
performed according to the technique suggested by Shaarawy et
al. (7). In the next stage phacoemulsification was performed
with implantation of intraocular lens (IOL) MA60BM, SA60AT,
SN60AT or SN60WF into the lens capsule.
The patients received an antibiotic with corticosteroid and
nonsteroidal anti-inflammatory drugs into the conjunctival sac
for 4 weeks after the procedure. Then, topical steroid drops
were applied again for 4 weeks to preserve the effect of the
surgery.
The investigated group was divided into two groups according to
the occurrence of hypotony within the first postoperative day or
its lack. The criterion of division was accepted at 6 mm Hg on
the basis of hazard coefficient ≈ 1.0. Group I (IOP ≤ 6 mm Hg)
included 50 eyes (40% of all cases), whereas group II (IOP > 6
mm Hg) included 75 eyes (60% of all cases). Demographic data of
both groups are demonstrated in table I.
Before surgery, the patients underwent distance and near
corrected visual acuity assessment (DBCVA, NBCVA), IOP was
measured using applanation tonometry method, anterior segment
was estimated in biomicroscope and fundus stereoscopy was
performed. After surgery the examinations were conducted on the
first and the 7, 30, 60, 90, 180, 360 and 450 day.
Surgery was considered a complete success when IOP was ≤ 12, 15,
18 mm Hg without glaucoma medication and a qualified success
when IOP was ≤ 12, 15, 18 mm Hg without or with maximum 2
antiglaucoma medications.
Statistical analysis was performed using t-Student test and
variance was analysed. The survival analysis was worked out with
Kaplan-Meier method using log rank and regression was analysed
with Cox proportional hazards model.
Results
IOP control
The mean IOP before surgery was in group one 19.5 ± 4. 5 mm Hg
and it decreased at the first postoperative day by 72.3% to the
value 5.4 ± 0.9 mm Hg (p < 0.001). After 15 months follow up
mean IOP was 12.5 ± 2.5 mm Hg and it was lower by 35.9% (p <
0.05) in relation to IOP before the surgery. Mean IOP in group
II was respectively before the procedure 20.3 ± 5.9 mm Hg and it
decreased at the first postoperative day by 38.5% to the value
12.6 ± 4.9 mm Hg (p < 0.001) . After 15 months follow up mean
IOP was 13.5 ± 2.0 mm Hg and it was lower by 33.5% (p < 0.05) in
relation to IOP before the surgery. In the whole follow up
period mean IOP values in group I were significantly lower than
in group II (p <0.05).
Glaucoma medications
The number of the administered antiglaucoma medications
decreased in group I from 2.28 ± 0.68 before surgery to 0.20 ±
0.64 after 15 months follow up (p < 0.05). Whereas in group II
it decreased from 2.29 ± 0.74 before the procedure to 0.26 ±
0.78 at the end of the follow up (p < 0.05).
At the end of 15 months follow up the difference between both
groups was statistically insignificant.
Surgical success rate
At the end of the follow up a complete success for the criterion
≤ 18 mm Hg was obtained in 94% of group I cases and in 72% of
group II cases (p < 0.013), a qualified success in 98% of group
I cases and in 88% of group II cases (p = 0.011) (Fig. 2). At
the same time for the criterion ≤ 15 mm Hg a complete success
was obtained in 81% of group I cases and in 57% of group II
cases (p = 0.001), whereas a qualified success in 84% of group I
cases and in 66% of group II cases (p = 0.001) (Fig. 3). For the
criterion ≤ 12 mm Hg a complete success was obtained in 41% of
group I cases and in 39% of group II patients (p < 0.015) and a
qualified success in 42% of group I cases and in 38% of group II
cases (p = 0.013) .
Best corrected visual acuity (BCVA)
BCVA in group I changed from 0.56 ± 0.28 before surgery to 0.84
± 0.24 after 15 months follow up, whereas in group II it changed
from 0.44 ± 0.27 to 0.71 ± 0.25. At first day post surgery BCVA
in group I was 0.45 ± 0.23 and in group II 0.47 ± 0.26. Both, at
first day 1 post surgery and at the end of the follow up no
significant differences were observed in visual acuity between
the investigated groups (p> 0.05).
Discussion
The safety of non-perforating operations results from the fact,
that during the procedure the opening of the eye anterior
chamber is not necessary. Owing to that, in the postoperative
period no anatomical changes are observed between the anterior
and posterior segment of the eye. Hypotony, being the
complication of perforated operations, becomes simultaneously
the limitation of their effects in long-term follow up due to
fibrosis (1, 2). Both, in the case of perforating and
non-perforating operations hypotony results from excessive
outflow of aqueous humour from anterior chamber in postoperative
period. However, in sclerectomy TDM provides outflow resistance
and prevents from excessive filtration and the resulting
hypotony is usually short-lasting and without changes of
anatomical relations (1,8,9) (Fig. 1). Sclerectomy is in fact
microtrabeculectomy, because during the Schelmm’s canal
deroofing there comes to perforation of its opposite wall
through septa connecting these walls (10). On the other hand,
the outflow of aqueous humour also takes place through
Descemet’s membrane, devoid of connective tissue. These two
elements decide on the technique of surgical procedure and
postoperative hypotony can be their derivative.
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In our observations,
mean IOP decreased at first day after surgery by 72.3% in group
I and by 38.5% in group II, and after 15 months follow up the
reduction of mean IOP was respectively 35.9% and 33.5%. In the
group of patients with hypotony, lower IOP values were obtained
throughout the whole follow up period and they differentiated
significantly the investigated groups (p= 0.014). Shaarawy et
al. (11) in similar study, in the group of patients with IOP 5.1
mm Hg at first day after surgery, noted reduction of mean IOP by
55.5% after 30 months and by 55.4% after 48 months of follow up.
However, it should be observed that mean initial IOP in this
group was 26.8 mm Hg, but at the end of the follow up period it
was 12.2 mm Hg and it was similar to the value obtained in our
study. The authors emphasize in other studies that obtaining low
IOP at first day of the surgery enables to obtain stable IOP in
many years follow up (7,12). Nevertheless, there is a question
whether IOP obtained in the group with hypotony is a sufficient
indicator proving correct functioning of TDM? Similarly as in
the case of trabeculectomy filtering bleb fibrosis also in
sclerectomy is a limitation in the surgery functioning, and the
established balance between aqueous humour filtration through
TDM and resistance of scleral flap and the remaining routes of
outflow decide of the effective IOP control. Thus, in this
aspect we analysed the success of the surgery according to the
criteria of IOP ≤ 12, 15, 18 mm Hg. In the case of the group
with hypotony a complete success was obtained respectively in
41, 81 and 94% of patients and the differences between the
investigated groups were statistically significant at all levels
(p < 0.05). Significant differences were also observed between
the investigated groups in the case of qualified success (p <
0.05) in group I it was 42, 84 and 98% respectively for the
criteria accepted for this study. Karlen et al. (13) in 38
months follow up noted a complete success in 44.6% of patients
with hypotony and a qualified success in 97.7% . However,
Shaarawy et al. (7) a complete success found in 61.9% of
patients, a qualified success in 94.8% of patients after 60
months of follow up and they confirmed their results in 8 years
follow up (14). In the mentioned studies a complete surgical
success was defined as IOP < 21 mm Hg without antiglaucoma
medications, a qualified surgical success as IOP < 21 mm Hg with
or without medications (7,12,13,14). Thus, it seems that
normally functioning TDM and at the same time not too aggressive
process of bleb obliteration enable to control IOP after surgery
at the level of 12 mm Hg which in our study concerned only 41%
of patients. In the remaining cases when IOP was regulated at a
higher level without medication we can assume that the cause of
this condition may be TDM dysfunction. Introduction of
medication results from progressing fibrosis of subconjuncitval
route of outflow, particularly that we did not find differences
between the number of applied medications after surgery in both
the investigated groups (p > 0.05). However, these conclusions
require confirmation in histological examinations of sclera and
Schlemm’s canal which we have not performed. The fact that the
surgical technique decides on the effectiveness of
non-perforating surgeries has been emphasized by numerous
authors (11,15,16,17,18). Rossier et al. and Vandaux et al.
think that appropriately deep excision of sclera guarantees IOP
stabilisation (17,18), while Jonescu-Cuypers et al. (15)
emphasize the surgeon’s experience and Mermound points to the
anatomy of iridocorneal angle (16). In our study hypotony was
obtained in the first postoperative day in 40% of patients,
while in the study of Shaarawy et al. (11) in as many as 61% of
patients from the investigated group. In the first postoperative
week in group I we observed decrease of BCVA resulting from
hypotony, which finally did not have any effect on the result
after 15 months. Similar tendency was observed in our previous
study and it was also confirmed by other authors (7). Hypotony
after phacodeepsclerectomy occurring directly after the
procedure seems to be a prognostic factor which proves proper
functioning of TDM. However, this conclusion requires
confirmation in histological examinations of TDM in the aspect
of its functioning after surgical procedure. Undoubtedly, the
occurrence of hypotony affects the results of survival and IOP
control in 15 months follow up.
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Praca wpłynęła do redakcji 15.08.2008 r. (1062)
Zakwalifikowano do druku 30.08.2008 r.
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