1. Purpose Methods
Results
Conclusions
Surgical options for a failed glaucoma drainage device
(GDD) are limited to placement of a second GDD or
diode laser cyclophotocoagulation. Primary GDDs are
usually implanted underneath Tenons layer. Favorable
results from placing a Baerveldt 250 mm2 GDD in the
supra-Tenons space directly underneath the conjunctiva
have been described previously1. We now extend this
concept to create a new procedure in which a failed
infra-Tenons GDD is replaced by a supra-Tenons GDD in
the same quadrant, thereby preserving conjunctival
tissue for future procedures. Results of this supra-
Tenons “tube exchange” procedure are compared to
those of a second infra-Tenons GDD in the infero-nasal
quadrant.
Supra-Tenons Placement of a Baerveldt Glaucoma Drainage Device in Eyes
with a Previous Infra-Tenons Glaucoma Drainage Device
California Pacific Medical Center, San Francisco, CA
Derek Huang, MD; H. George Tanaka, MD
We identified twelve patients who underwent a tube
exchange (TX) and ten who underwent placement of a
second tube (TT). There were no statistically significant
differences in age, sex, race, glaucoma type, prior
surgeries or pre-operative IOP. The tube exchange group
had a higher mean pre-operative IOP and were using
more glaucoma medications.
Both groups showed a significant drop in IOP following
surgery with a p-value of 0.0003 in the TX group and
0.05 in the TT group. The mean post-operative IOP was
11.8 mmHg in the TX group and 14.2 mmHg in the TT
group. The number of post-operative glaucoma
medications was 2.25 and 2.8 in the TX and TT groups,
respectively. Converted visual acuity was 20/115 for the
TX group and 20/158 in the TT group. These differences
were not statistically significant.
Post-operative complications included hyphema (2),
vitreous obstruction (1), wound leak (1), and corneal
endothelial damage (1) in the TX group and corneal
decompensation (3) and iris obstruction (1) in the TT
group. No patients in either group developed tube
erosions. One patient in the TX group and three
patients in the TT group required additional glaucoma
procedures for IOP control.
Our results suggest that in patients with a failed GDD,
supra-Tenons tube exchange in the same quadrant
provides similar clinical outcomes to placing a second
GDD in a different quadrant. Equivalent IOP results
were seen in spite of using a smaller 250 mm2 GDD for
the tube exchange and placing the new GDD directly
over the previous surgical site. Tube exchange preserves
conjunctival tissue for future surgery and results in less
hardware in the eye. Shortcomings of this study include
its retrospective nature, low number of study subjects
and relatively short follow up period. Further studies
are needed to confirm that tube exchange is a viable
surgical alternative to placement of a second GDD or
cyclodestructive procedures.
References
1. Sy A and Tanaka G. Supra-Tenon Capsule Placement of Baerveldt Implant. Poster
presentation at the 25th American Glaucoma Society Annual Meeting, Coronado, CA.
February 27, 2015.
The tube exchange surgical technique is demonstrated
at: https://www.youtube.com/watch?v=Zjh9bSXkQwI
We performed a retrospective chart review of consecutive patients
who had a supra-Tenons tube exchange (TX group) and compared
them to a group of patients who underwent placement of a second
infero-nasal GDD (TT group). All surgeries were performed by one
surgeon. (GHT) Main outcome measures were post-operative IOP,
number of glaucoma medications, and logMAR visual acuity. The t-
test was used to compare the groups.
Mean pre- and post-operative IOPs in the two groups. The tube exchange group
had a higher mean pre-operative IOP but a lower post-operative IOP compared to
the second tube group.
Derek Huang, MD: No Financial Disclosures
H. George Tanaka, MD: Allergan, Alcon, Merck,
iScience, Glaukos
Tube Exchange
(N=12)
Second Tube
(N=10)
P-value
Mean (median)
Mean
(median)
Demographics
Age 61 (63) 67 (64) 0.30
Gender (M:F) 2.7:1 2.3:1
Baseline
Characteristics
Number of prior
surgeries
4.33 (5) 4 (3.5) 0.67
Length of follow
up (months)
11.33 (10) 25.3 (24.5) 0.02
Pre-IOP 23 (22) 18.8 (17.5) 0.17
# of meds pre-
procedure
4 (4) 3.1 (3.5) 0.05
Pre-operative
Visual Acuity
(logMAR)
0.31 (0.3) 0.62 (0.3) 0.18
Table 2 shows the IOP, number of glaucoma medications, and visual
acuity after surgery in the tube exchange and second tube groups.
Tube
Exchange
(N=12)
Second
Tube
(N=10) P-value
Mean
(median)
Mean
(median)
Outcome
measures
Post-IOP 11.8 (12) 14.2 (5.5) 0.21
# of meds post-
procedure
2.25 (2) 2.8 (3) 0.40
Post VA
(logMAR)
0.76
(0.60)
0.90
(0.43)
0.72
Number of glaucoma medications before and after surgery. The tube exchange
group was using more medications before surgery and less medication after
surgery compared to the second tube group.
Table 1 shows the baseline characteristics of patients included in the
study.
Results
4
3.1
2.25
2.8
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Tube Exchange Second Tube
# of Meds Pre-
Procedure
# of Meds Post-
Procedure
23
18.8
11.8
14.2
0
5
10
15
20
25
Tube Exchange Second Tube
Pre-IOP
Post-IOP
P = 0.0003 P = 0.05