Evaluation of Bleb Fluid After Baerveldt Glaucoma Implantation Using Magnetic Resonance Imaging
Kentaro Iwasaki,1 Masayuki Kanamoto,2 Yuji Takihara,1 Shogo Arimura,1 Yoshihiro Takamura,1 Hirohiko Kimura,3 Masaru Inatani1
1Department of Ophthalmology, University of Fukui, 2Radiological Center, University of Fukui Hospital, 3Department of Radiology, University of Fukui.

PurposeThe purpose of the present study was to assess
the bleb structure after tube-shunt surgery
using a 350-mm2 endplate Baerveldt
glaucoma implant, and to determine theparameters of bleb images that correlated withpostoperative IOP in a large sample size.

Methods
Design: Cross-sectional observational caseseries.
Setting: Fukui University Hospital, Japan.
Study population: Patients who had undergone
tube-shunt surgery using the 350-mm2 endplate
Baerveldt glaucoma implant.
Observation: T2-weighted images of bleb fluid
were scanned with 3 Tesla magnetic resonanceimaging (FIESTA-C) in 52 patients
Primary Outcome: The primary outcome
measure was the classification of bleblayer formation.

Secoundary Outcome: The secondary
outcome measures included relationshipsbetween the parameters of bleb images(bleb volume or classification based on thestructure) and preoperative patient data,
endplate position, and postoperative IOP.

Results
In total, 52 blebs were evaluated.
Primary Outcome
In all cases, a curvilinear low-intensity bandthat corresponded to the signal intensity of thesilicone material was observed at the locationof the endplate. Areas with the same highintensity as the intraocular fluid, corresponding
to the signal intensity of the aqueous humor in
the filtering bleb, were located adjacent to theendplate. In 28 out of 52 eyes (53.8%), thesignal corresponding to the aqueous humor in
the filtering bleb was detected on the outsideof the endplate. The remainder of the eyes
(46.2%) showed aqueous humor signals on
both sides of the endplate. Based on thisinformation, we classified the eyes into twogroups: the single bleb layer group and thedouble bleb layer group (Fig 1).

Secoundary Outcome
Relationships between the parameters of bleb
images and postoperative IOP
The mean ± standard deviation bleb volume was
0.23 ± 0.15 cm3 (n = 52). There was nosignificant correlation between bleb volume andpostoperative IOP (r = –0.080; P = 0.57) .
Comparisons of postoperative IOPs between thesingle bleb layer group and the double bleb layergroup revealed significantly lower postoperative
IOPs in the double bleb layer group than the single
bleb layer group (12.3 ± 3.8 mmHg vs. 14.7 ±4.1 mmHg, respectively; P = 0.033). Comparisonof bleb volumes between the two groups showed asignificantly larger mean bleb volume in thedouble bleb layer group than that of the single bleblayer group (0.28 ± 0.2 cm3 vs. 0.19 ± 0.1 cm3,respectively; P = 0.024)

Comparison of patient characteristics between thesingle bleb layer and double bleb layer groups
Among the preoperative data, there was a significant
difference in the number of intraocular surgeries
before Baerveldt glaucoma implantation between thetwo groups. The single bleb layer group had
undergone more intraocular surgeries before
Baerveldt glaucoma implantation than the double
bleb layer group (2.8 ± 1.4 vs. 1.9 ± 0.8,respectively; P = 0.0068).

Determinants for the single/double bleb layer
Multivariate analyzes using Logistic regression
models showed that a higher number of previous
intraocular surgeries was significantly associatedwith the formation of a single bleb layer (relative risk
[RR], 2.85; P = 0.0014).

Conclusion
Figure 1. MRI scans of eyes with the Baerveldt
glaucoma implant(A) A case with a single bleb layer.
(B) A case with a double bleb layer.
A curvilinear low-intensity area was observed at
the location of the endplate (arrows). A highintensity area corresponding to the aqueous humor,
was located adjacent to the endplate (arrowheads).

In conclusion, Baerveldt glaucoma implantation
results in either a layer of bleb fluid on each sideof the endplate or one layer outside the endplate.
Lower postoperative IOPs are associated with theformation of the double bleb layer, not a larger
bleb volume. Repeated intraocular surgery may
cause the formation of the double bleb layer to fail,resulting in a higher IOP after Baerveldt glaucoma
implantation.
Iwasaki K et al. Sci Rep. 2017