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A
ngle
-
closure
glaucoma
:
diagnosis
R
ev
A
ssoc
M
ed
B
ras
2014; 60(3):192-195
193
nus), where the aqueous fluid has access to drainage pa-
thways. This is the most important exam for the classifi-
cation of glaucoma, and it is used as a reference for the
evaluation of the anterior chamber angle configuration.
The identification of all anatomical details of the came-
rular sinus allows the assessment of crucial aspects for
diagnosis of several types of glaucoma
3
(
D
). Performed
using lenses (direct gonioscopy) or by using the image re-
flected on a mirror attached to the lens (indirect gonios-
copy with 1-4 mirror lens), it allows to establish whether
a particular angle is open or closed, and if closed, to what
extent
4
(
D
). It also allows, through maneuvering (inden-
tation), differentiation between the overlapping of the
iris and the outer surface of the camerular sinus, and true
goniosynechia. Nevertheless, the findings of gonioscopy
may be compromised by excessive pressure on the lens or
intensity of lighting, which tends to increase the opening
angle of the anterior chamber.
UBM, a diagnostic method described in the early
1990s, uses a high frequency transducer (50-100 MHz),
thus permitting an axial and lateral resolution of around
20 to 40 micra, even though at the expense of a reduction
in ultrasound penetration (approximately 5 millimeters)
5
(
C
). The theoretical advantages of the method are the pos-
sibility of evaluating retro iridian structures and perfor-
ming quantitative measurements of the camerular sinus.
Its main limitations are: high cost, the dependence of a
qualified examiner, the observation of a restricted region
of the camerular sinus, and the need for dipping the ul-
trasound probe
4
(
D
).
In a study involving Chinese subjects with suspec-
ted primary angle closure (characterized as the inability
of seeing through gonioscopy the pigmented portion of
the trabecular meshwork at 180 degrees or more), the
overlapping of the iris and the outer surface of the came-
rular sinus was most commonly detected by UBM than
gonioscopy. The prevalence of overlapping found using
UBM totaled 15.4% in patients with angle grade 4 Shaf-
fer, 45% in those with grade 3, 71% in grade 2, 70.2% in
grade 1, and 86.4% in grade 0
6
(
B
).
Despite published papers on the use of UBM, the li-
terature lacks studies with adequate design and sample,
comparing the use of gonioscopy and UBM for the diag-
nosis of angle-closure glaucoma
7-10
(
B
)
4
(
D
).
Recommendation
UBM proved to be a useful method for quantitative eva-
luation of camerular sinus and its structures and may
complement, but not replace, the semi-quantitative analy-
sis done by gonioscopy.
C
an
anterior
segment
optical
coherence
tomography
(
as
-
oct
)
replace
gonioscopy
in
the
diagnosis
of
patients with
angle
-
closure
glaucoma
?
The assessment of the dimensions and configuration of
the anterior chamber angle makes up an essential part of
the diagnosis and monitoring of patients with closed an-
gle. As previously mentioned, indirect gonioscopy has
been used as a traditional method and reference test for
the diagnosis of primary angle-closure glaucoma. Howe-
ver, this method has limitations, which are mainly depen-
dent on the examiner’s experience
11
(
C
). AS-OCT opera-
tes by a mechanism similar to ultrasound but uses a beam
of light instead of sound waves to study the depth of tis-
sues
12
(
D
). The initial description of this non-invasive and
non-contact method applied in the study of ocular struc-
tures was made in 1991 and, since then, several studies
have reported its utility in the evaluation of anterior and
posterior segments of the eye
7,13-15
(
B
)
16
(
D
). AS-OCT al-
lows for the documentation and evaluation of the profi-
le of the iris and its relations with other anatomical struc-
tures of the anterior segment
17
(
D
). Its main limitations
are due to the impossibility of assessing retro iridian struc-
tures and the high costs.
Furthermore, comparisons between the efficiency
of gonioscopy and anterior segment tomography in the
study of sinus camerular studies are rare. Analyzing in-
dividuals with a mean age of 62.5 years, mostly Asians
(85.7% Chinese), with suspected angle closure or confir-
med primary angle closure (some of whom had been trea-
ted by iridotomy), who underwent OCT and gonioscopy,
there is greater sensitivity of OCT (98%) in the detection
of closed angles (≥ 1 quadrant in one or both eyes) com-
pared with gonioscopy (68%)
18
(
B
). Regarding specificity,
the values observed for gonioscopy (96%) were higher com-
pared with OCT (55%), with a positive likelihood ratio
of 1.8 and 17 for OCT and gonioscopy, respectively
18
(
B
).
On the other hand, a study analyzing subjects with a
mean age of 61 years (SD = 7.6 years) mostly Asians (92%
Chinese), and without ophthalmic complaints (no sus-
pected or confirmed angle closure), who underwent go-
nioscopy and OCT in order to detect closed angles (Scheie
III or IV), identified through the analysis of the four qua-
drants of the right eye sensitivity and specificity of 66%
and 79%, respectively, in gonioscopy with likelihood ratio