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Ultrasound Biomicroscopy and Anterior Segment optical Coherence Tomography in the diagnosis and Management of Glaucoma

  • Hospital Egas Moniz (West Lisbon Hospitals Center Portuguese NHS)

Abstract and Figures

We aimed to summarize the applications, strengths and weaknesses of two anterior segment imaging modalities: the ultrasound biomicroscopy (UBM) and the anterior segment optical coherence tomography (AS-OCT) in the diagnosis and surgical management of glaucoma. This narrative review was based on our clinical experience with these technologies supported on scientific literature review through Medline via PubMed®. The syntax used in the search was “Glaucoma AND Anterior Chamber Angle AND Ultrasound Biomicroscopy OR UBM AND Anterior Segment Optical Coherence Tomography OR AS- OCT”. Publications were selected based on relevance and no redundancy, and authorship from 2007-2014. Additionally, UBM and AS-OCT images were selected from two of the authors’ personal archives to illustrate prevalent glaucoma findings and post- operatory using both technologies. AS-OCT and UBM share overlapping characteristics and are both useful in glaucoma diagnosis and post- operative assessment. However, particular technical features of each will direct the best application to clarify specific glaucoma etiologies, to guide in the most effective management and to explain glaucoma surgical outcomes.
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Filipe HP et al. UBM and AS-OCT in the diagnosis of glaucoma.
Ultrasound biomicroscopy and
anterior segment optical coherence
tomography in the diagnosis and
management of glaucoma
We aimed to summarize the applications,
strengths and weaknesses of two anterior segment
imaging modalities: the ultrasound biomicroscopy
(UBM) and the anterior segment optical coherence
tomography (AS-OCT) in the diagnosis and surgical
management of glaucoma.
This narrative review was based on our clinical
experience with these technologies supported
on scientific literature review through Medline
via PubMed®. The syntax used in the search was
“Glaucoma AND Anterior Chamber Angle AND
Ultrasound Biomicroscopy OR UBM AND Anterior
Segment Optical Coherence Tomography OR AS-
OCT”. Publications were selected based on relevance
and no redundancy, and authorship from 2007-2014.
Additionally, UBM and AS-OCT images were
selected from two of the authors’ personal archives
to illustrate prevalent glaucoma findings and post-
operatory using both technologies.
AS-OC T and UBM share overlapping characteristics
and are both useful in glaucoma diagnosis and post-
operative assessment. However, particular technical
features of each will direct the best application to
clarify specific glaucoma etiologies, to guide in the
most effective management and to explain glaucoma
surgical outcomes.
Key Words: Glaucoma, Anterior Chamber Angle;
Ultrasound Biomicroscopy; UBM; Anterior Segment
Optical Coherence Tomography; AS-OCT
Detailed evaluation of anterior segment
structures is an integral part of ophthalmic
examination, particularly in patients with glaucoma.
Optical biomicroscopy and gonioscopy have been
classically used to assess anterior segment and
anterior chamber angle structures, and how they
relate to one another.
The innovative development of anterior segment
imaging has allowed physicians to visualize anterior
segment, angle structures, and aspects relevant to
diagnosis and management of glaucoma, which
could not be assessed by conventional techniques.
We aimed to summarize the applications,
strengths and weaknesses of two anterior segment-
imaging modalities: ultrasound biomicroscopy
(UBM) and anterior segment optical coherence
tomography (AS-OCT). This narrative review
was based on our clinical experience with these
technologies supported on scientific literature
review through Medline via PubMed® to support
our findings in practice setting. The syntax used in
the search was “Glaucoma AND Anterior Chamber
Angle AND Ultrasound Biomicroscopy OR UBM AND
Anterior Segment Optical Coherence Tomography
OR AS-OCT”. Publications were selected based on
relevance and no redundancy, and authorship from
UBM and AS-OCT images were obtained from an
image library from the priv ate practice of the first and
second authors (HPF and MC) to illustrate prevalent
glaucoma findings and post-operatory features with
both technologies. All images were re-identified
prior to being considered for this publication.
Additionally, images were enhanced (brightness,
contrast, resolution, and orientation) to improve its
didactic purposes using Adobe Photoshop™ version
CS 5.1 software.
Helena Prior Filipe1, 2, 3, Manuela Carvalho3, Maria da Luz Freitas 4,
Zélia Maria Corrêa5
1. Hospital of the Armed Forces. Department of Ophthalmology. Lisbon Portugal
2. ALM, Medical and Surgical Ophthalmology Clinic Lisbon, Portugal
3. Hospital of SAMS. Department of Ophthalmology. Lisbon, Portugal
4. Hospital of Arrábida, Department of Ophthalmology. Porto, Portugal
5. Department of Ophthalmology, University of Cincinnati College of Medi-
cine, Cincinnati, OH, USA
Corresponding author: Helena P Filipe, MD
Rua Sargento José Paulo dos Santos nº 8 1800-331 Lisboa, Portugal, UE
Phone: +351967061457
Funding: None
Proprietary/financial interes: None
Date of submission: 13/01/2016 Date of Approval: 21/04/2016
Vis. Pan-Am. 2016; 15(2): 37-42.
frequencies. Ultrasound waves travel well through
the iris and ciliary body pigment epithelia allowing
the acquisition of high-resolution images of
structures behind the iris and the ciliary body. The
same does not apply to light beams, which are
highly bsorbed by the pigmented posterior layer
of the iris preventing a good visualization of the
retroiridian structures , sometimes essential for an
accurate diagnosis.1-5
The first commercialized UBM machine
(Paradigm Medical Industries, Salt Lake Cit y, UT) with
a 50 MHz probe, offered anterior segment quadrant
images of 25 μm (axial) x 50 μm (transversal)
resolution. Presently, machines as OTI (Ophthalmic
Technologies, Toronto, Canada), VuMax II (Sonomed,
Inc., Lake Success, NY, USA) and New Reflex™
(Reichert® Ultrasound Biomicroscope, Reichert
Technologies, USA) allow the acquisition of a 180º
image in a single frame permitting a comprehensive
qualitative and quantitative appreciation of the
anterior chamber. More recently, ultrasound devices
using a 80-MHz probe (Iscience, Mountain View,
CA) can image the Schlemm’s canal and trabecular
meshwork. However, the higher frequencies used,
the less tissue penetration we obtain, the best
quality eye wall images and the worse for posterior
to the iris. The ultrasound transducer needs to be
immersed in a coupling medium, either by using an
eyecup or a disposable water-filled small cap fixed
to the hand piece allowing the examination in the
sitting position. The ultrasound beam reaches the
anterior segment structures with minimal obstacle
and the reflected echoes generate a bi-dimensional
image. Topical anesthesia and patient cooperation
are essential during examination.5-7
AS-OCT is based on low-coherence
interferometry, that consists on the emission
of one infrared laser light beam by a super
luminescent diode. This is then split in two sub-
beams: one is directed towards the biological sample
and the other one to a mirror on the reference arm
that must be mechanically scanned to get range
information. Analysis of the reflection delay from the
sub-beams as they travel through these structures
is called time-domain technology or TD-OCT.
The Visante OCT (Carl Zeiss Meditec, Inc, Dublin,
California) works through this technology with a
light source of approximately 1310 nm.
In spectral domain OCT (spectral Fourier-
domain or SD/FD-OCT), the combined light beams
are passed through a grating that breaks it into a
spectrum, which is recorded by the line camera.
Fourier analysis is applied to the spectrum to return
it to the spatial domain and form the OCT image.
Spectralis OCT (Heidelberg Engineering GmbH,
Heidelberg, Germany) is based on this technology
and works with a wavelength of 840 nm.
The swept-source OCT or SS-OCT was developed
from SD-OCT and allows a full 360º assessment of the
anterior chamber angle. It works with a frequenc y swept
light source of 1050 nm and a high speed detector to
capture the interference signal as a function of time,
instead of a spectrometer and camera as in spectral-
domain technology. The higher speed imaging avoids
shadowing artifac ts, enables a better tissue penetration
and consequently a better visualization of the anterior
chamber angle through the sclera. Through the use
of Fourier transformation, swept-source and spectral
domain-OCT work faster than TD-OCT because no
mechanical scanning is involved.1-4
AS-OCT provides a resolution, of 18 μm (axial)
x 60 μm (transversal) for time domain AS-OCT
Visante (TD OCT) and as high as 5 μm (axial) x 7 μm
(transversal) for spectral/Fourier domain devices
(SD/FD systems).2,8
The claimed advantage of AS-OCT is its non-
contact scanning method performed in the sitting
position, whereas UBM requires eye contact through
a coupling medium, many times requiring supine
position, topical anesthesia and significantly more
patient cooperation.1
I. Characterization of Anterior Segment
A. Angle Closure Glaucoma
Primary angle closure glaucoma is a
heterogeneous group of eye diseases caused by
a variety of mechanisms. It can be categorized
according to the mainly involved anterior segment
structure showing abnormalities related to size
or position or as a result of abnormal forces in the
posterior segment (Table 1).7,9
This mechanism customarily leads to iris
apposition to the trabecular meshwork and
subsequent increase in intraocular pressure.
High resolution images provided by AS-OCT and
especially UBM can unveil the structure involved in
the underlying mechanism and guide to the most
effective management approach.7,9
A.1. Primary Pupil Block
It is known that aqueous humor flow resistance
at the irido-lenticular contact increases the
We discuss the importance
of anterior segment imaging
in characterizing anterior
segment morphology in angle
closure glaucoma and trauma,
in understanding the effect
of lighting conditions and age
on anterior segment angle
and in secondary open angle
glaucoma. We summarize
aspects related to quantitative
imaging in glaucoma and
discuss the relevance of anterior
segment imaging in glaucoma
surgical outcomes assessment.
Technology and Technique
Since its development,
ultrasound biomicroscopy
(UBM) has played a dominant
role in objective imaging of
the anterior chamber angle
until anterior segment optical
coherence tomography (AS-
OCT) was introduced in 2003.1
Ultrasound biomicroscopy
(UBM) is based on the emission
of a high-frequency ultrasound
beam (35-80 MHz) enabling high-
resolution cross sectional images
of anterior segment. Ultrasounds
at 50 to 80 MHz have axial
resolutions of approximately 50
to 20 µm, whereas a frequency
of 10 MHz has a resolution of
approximately 150 µm. The
higher the frequency, the lower
the penetration depth, which
is about 4-3mm for higher
Figure 1. UBM composite showing occludable angle related to primary pupillary block. (Top left); plateau iris, the angled iris root
pushed forward against the trabecular meshwork by an anteriorly rotated ciliary body (Top right); a thickened lens and a flattened
iris displaying a Mount Vesuvius configuration associated with phacomorphic glaucoma. (Center left); AS-OCT illustrating a plateau
iris, imaging of the ciliary body and its influence on the anterior chamber angle are not seen in so much detail with AS-OCT (Center
right); UBM reveals conjunctival oedema, the uveal effusion (thickened ciliary body and anterior choroid) pushes forward the anterior
segment structures and determines angle closure (Bottom left); AS-OCT reveals supra-ciliary and supra-choroidal effusion pushing
forward the lens equator to flatten the irido-ciliary sulcus and the posterior chamber and cause angle closure. Note the difference
in range and resolution between the two technologies (Bottom center); AS-OCT shows extreme forward positioning of the anterior
segment structures, flat anterior chamber (athalamia), iris and lens contact with the corneal endothelium (Bottom right).
Filipe HP et al. UBM and AS-OCT in the diagnosis of glaucoma.
pressure in the posterior chamber, widens
its area and produces an anterior iris bowing
leading to angle closure (Figure 1. Top left).7
UBM and AS-OCT confirm diagnosis and
document pressure balance restoration between
both anterior and posterior chambers after laser
peripheral iridotomy (LPI). Anterior segment
imaging can also explain the reasons whereby
this procedure is unsuccessful in some angle
closure situations such as incomplete LPI,
goniosynechiae and plateau iris syndrome.
Iris-trabecular apposition disclosed by
gonioscopy, UBM or AS-OCT does not necessarily
imply an intraocular pressure increase. Iris-
trabecular meshwork contact may be intermittent
or relatively short (less than 360o and or not
reaching the Schwalbe’s line) and the uveoscleral
route may represent approximately 10% of
drainage. Usually, mydriasis is associated with an
iris root aqueous volume decrease. In eyes prone
to angle-closure glaucoma, this phenomenon
can be compromised and even be a precipitating
factor.10-13 Considering the latter two aspects,
it is possible to infer the relevance of assessing
iris thickness and standardizing test lighting
conditions when using UBM or AS-OCT for
quantitative assessments.
A.2. Plateau Iris
UBM and AS-OCT typically show a thick, flat or
slightly anterior bowed iris, which abruptly ascends
after its insertion on the ciliary body’s anterior
surface assuming a “square root” appearance.
Indentation gonioscopy or UBM may reveal the
double-hump sign. The most peripheral hump
drapes over the rigid, anteriorly positioned ciliary
body, and the central rests over a long extension
on the anterior lens surface. A modified dynamic
gonioscopy procedure using AS-OCT allowed
the conclusion that anterior chamber angle
(ACA) amplitude was significantly higher after
indentation and that indirect signs were reliable to
suggest a plateau iris. Anterior rotation of the ciliary
body, best observed with UBM, is associated with
anterior positioning of the iris dilator’s anchorage
point and determines: iridociliary sulcus narrowing,
iris apposition to the trabecular meshwork and
angle closure. The farther away the iris dilator “joint”
from the scleral spur, the lower the probability of
angle closure. The central depth of the anterior
chamber is usually normal (Figure 1. Top right and
center right). 11, 14, 15
UBM and AS-OCT images can also be useful
to assess the effect of argon laser peripheral
iridoplasty on the ACA allowing objective anterior
segment measurements.
A.3. Phacomorphic Glaucoma
UBM and AS-OCT can confirm the presence
of an intumescent lens pushing forward the
iris, which can assume a “Mount Vesuvius
configuration”, and the ciliary body determining
iris/trabecular meshwork apposition. An increased
lens vault elevates the probability of progression
to angle-closure glaucoma, regardless of lens
thickness and location (Figure 1. Center left).16
A.4. Uveal Effusion/Malignant Glaucoma
Very small eyes, especially nanophthalmos, are prone to angle
closure due to their dimensions, unsuccessful regulation mechanisms,
and vitreous resistance to fluid flow. All these concur to create expansion
of choroidal volume and consequently high posterior lenticular pressure
promotes extreme forward positioning of anterior segment structures.
This mechanism leads to maximal resistance to aqueous humor flow
and intraocular pressure rise. UBM and AS-OCT document lens, iris and
vitreous anteriorly positioned, absence of posterior chamber, markedly
reduced anterior chamber depth until athalamia, and uveal effusion
(Figure 1. Bottom left, center and right). 11,16
A5. Other Causes of Angle Closure
Primary or secondary cystic or solid lesions of the iris and/or
ciliary body, goniosynechia, cyclitic membrane, vitreous hernia, or
post-vitreoretinal surgery using vitreous tamponade (silicone oil or
gas) may trigger partial or intermittent angle closure that can be
documented by UBM and AS-OCT (Figure 2).
A6. Other structural aspects
When evaluating an eye with a history of trauma, UBM is particularly
important if optical media are not transparent (hyphema or hypopyon)
and can reveal angle recession or cyclodialysis, potentially explaining
respectively intraocular pressure increase or decrease after the injury
Site of aqueous
humor obstruction Angle closure glaucoma
Iris Primary Pupil Block
Ciliary Body Plateau Iris
Lens Phacomorphic Glaucoma
Suprachoroidal Fluid Uveal Effusion / Aqueous Misdirection
Table 1. Classification of angle closure glaucoma according to Ritch. The four anatomic sites where aqueous flow obstruction may occur.
Figure 2. Left UBM images reveal secondary angle closure due to the presence of a single or multiple retro iridian cysts. Note the pseudo
plateau configuration in the down left image. Top right UBM image illustrates an iris tumor. Down right UBM image shows a gonio-
synechia (black arrow)
Vis. Pan-Am. 2016; 15(2): 37-42.
(Figure 3). UBM might be problematic to
use in recent perforating trauma or early
post-operative period. As a noncontact
technology, AS-OCT is potentially a better
option to avoid potential complications
related to wound healing or intraocular
A6.2. Effect of Lighting Conditions
and Age
Lighting conditions may cause relevant
variation in the anterior segment topography.
Additionally, anterior movement of the lens
has been estimated to be approximately 20
μm/year with increasing age. This is associated
with a progressively increasing intumescence
of the lens, reduced anterior chamber
depth and ACA narrowing. The mechanism
is clinically more significant in eyes with
anatomical predisposition to angle closure,
such as in hyperopia, nanophthalmos, plateau
iris, and others.16, 17
B. Secondary Open-Angle Glaucoma
The diagnostic triad of pigmentary
glaucoma consisting of Krukenberg spindle,
radial transillumination defects and trabecular
meshwork pigment is caused by pigment
dispersion due to mechanical friction bet ween
posterior iris surface and zonule. Both UBM
and AS-OCT may reveal a back bowing iris
touching zonular filaments, creating a “reverse
pupillary block ”. In these cases, laser peripheral
iridotomy, flattens the iris, confirming
balanced pressure gradient between anterior
and posterior chambers (Figure 4).18
II. Quantitative Imaging
in Glaucoma
Anterior segment measurements have attained
increased objectivity, accuracy and reproducibility
since Pavlin’s first biometric descriptors were
published. The concept rapidly extended to AS-
OCT. The scleral spur is the landmark from which
many measurement parameters are estimated. After
its manual localization and application with a semi-
automated software system, the anterior chamber
angle can be quantitatively characterized in a fast
and reproducible manner. However, identifying
the scleral spur in angle closure cases may be
challenging, especially in the upper and lower
quadrants. UBM can be a better option in such
cases, due to the ultrasound waves ability to travel
through pigment bearing tissue and better reveal
retro-iridial structures. Research is under way to
find one or a set of effective biometric descriptors
to accurately diagnose angle occlusion and predict
angle closure glaucoma probability.1,6, 7,12,19,20
III. Assessment of Glaucoma
Surgery Outcomes
UBM and AS-OC T substantially complement
slit lamp biomicroscopy in assessing filtering blebs’
features. Yamamoto has proposed a classification
system correlating filtering bleb ultrasound
characteristics and bleb function. The internal
echographic structure of the filtering bleb and the
presence of an intra-scleral route have shown good
correlation with intraocular pressure control (type
L bleb). Based on AS-OCT, Labbé et al. defined four
types of filtering blebs according to its morphology
and internal reflectivity: diffuse, microcystic, flattened
and encapsulated. Good intraocular pressure control
has been shown on diffuse and microcystic filtering
blebs similar to the findings illustrated in Figure 5.21-24
Correlation between in vivo confocal microscopy
findings and filtering bleb reflectivity (AS-OCT)
with filtering glaucoma surgery outcomes, has
suggested that heterogeneous, lower reflective
supra-scleral tissues match with loose connective
tissue, where gaps and high fluid content abound
thus documenting a functional bleb.25
UBM and AS-OCT can also assess several other
glaucoma surgery-related aspects such as the
patency of the glaucoma filtering surgery internal
ostium; the effect of LPI on anterior chamber
morphology; the trabeculo-Descemet window
integrity and thickness; the presence of intra-scleral
route; the intra- and supra-scleral “lake” dimension;
the fluid in supra-choroidal space; the patency,
route and relation of aqueous drainage devices
with neighboring structures and the cause for
non-functioning glaucoma filtering surgery (Figure
5).26 More recently, very high frequency probes (80
MHz) enabled the identification of Schlemm’s canal,
Figure 3. UBM image illustrates post-traumatic anterior chamber angle recession without complete separa-
tion of the iris and ciliary body (cyclodyalisis) but associated with supra-ciliary oedema.
Filipe HP et al. UBM and AS-OCT in the diagnosis of glaucoma.
confirming it’s opening after surgical viscocanaloplasty.
IV. Ultrasound Cyclocoagulation
High Intensity Focused Ultrasound (HIFU) is already
being used to treat refractory glaucoma. Ultrasound waves
are transmitted through a circular microdevice with six
piezoelectric transducers that focus ultrasound emission
on the ciliary body, promoting precise cyclocoagulation.
Evidence shows the efficacy of this therapy in achieving
intraocular pressure control and improved tolerability
when compared to other cyclodestructive techniques.
Morphological alterations produced by circular ultrasound
cyclocoagulation can be evaluated using UBM.27
UBM or AS-OCT enable anterior chamber width (ACW)
measurements to select the best ring diameter for direct use
on the ciliary body.28
Concluding Comments
Our clinical experience shows that AS-OCT and UBM
share overlapping features and both are useful in glaucoma
diagnosis and surgical assessment. This is in accordance to
the literature reviewed. However, specific technical features
of each technology such as axial and transversal resolution,
visualization of retro-iridial structures, detailed appreciation of
tissue microstructure and an easy faster non contact imaging
acquisition tend to determine the choice of technology used
according to the information the examiner is specifically
looking for (Table 2). Examiner and patient biases should also
be recognized and considered when selecting the imaging
method to be employed. User biases include examiner
experience, degree of comfort using a certain technology and
availability of that technology. Patient biases include comfort,
cooperation and other occupational circumstances.
Both technologies provide real time high resolution cross
sectional images of the anterior segment including the ACA
upon which biometric descriptors can be used for quantitative
characterization, diagnosis, and surgical management of
glaucoma. Best advantage of AS-OCT over UBM is that it is a
friendly user, reproducible and swift noncontact technology.
UBM classically requires a supine position, immersion, time,
patient collaboration and a skilled operator. On the other hand,
UBM’s major advantage lies on the ultrasound beam’s ability
Figure 4. AS-OCT shows a back bowing iris that causes zonular fibers friction and a reverse pupil block associated with pigmentary glaucoma (Left). AS-OCT image illustrates
the iris flattening after laser periphery iridotomy and reverse pupil block resolution (Right).
Figure 5. Post-operative findings after non-penetrating deep sclerectomy (NPDS) evaluated by UBM
(Left column) and AS-OCT (Right column). Polycystic blebs feature low reflective supra-scleral tissues
with multiple coalescent low reflective spaces (First row). Diffuse filtering blebs present low reflective
supra-scleral tissues, intra-scleral lake and a trabeculo-Descemet window (Second row). Flattened
filtering blebs feature high reflective supra-scleral tissues, intra-scleral lake and route and a thin
trabeculo-Descemet window (Third row). Encapsulated filtering blebs present high reflective supra-
scleral tissue and a contained lake (Forth row).
Vis. Pan-Am. 2016; 15(2): 37-42.
to travel through iris pigment epithelium
allowing a good view of retro-iridial structures
as the ciliary body, posterior chamber, zonule,
anterior vitreous and lens posterior capsule.
UBM can also provide high resolution imaging
through opaque media.
Despite these high-resolution techniques
with digital capabilities that enhance our ability
to evaluate and share acquired dynamic images
of anterior segment, we can still wonder about
the prevailing technology in glaucoma imaging.
Based on our experience and literature review, we
are certain that both complement each other.
1. Ursea R, Silverman RH. Anterior Segment Imaging
for assessment of Glaucoma. Expert Rev Ophthalmol.
2. Schuman JS. Spectral Domain Optical Coeherence
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3. Huang D, Swanson EA, Lin CP, Schuman JS, Stinson
WG, Chang W, Hee MR, Flotte T, Gregory K,
Puliafito CA et al. Optical coherence tomography. Sci-
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Performance Advantages
Both technologies
- Provide evidence
of contributing
mechanisms and
principal structures
causing angle-
closure glaucoma
to decide the best
effective treatment
- Characterize
anterior segment
using measurement
parameters as
valuable screening,
and treatment
assessment tools
- Illustrate how the
complex ciliary
body/ iris– ACA
changes with age,
accommodative and
light stimuli
- Assess glaucoma
ltering surgery
- Provides high-resolution
cross sectional images of
anterior segment and ACA
including structures behind
the iris such as the ciliary
body, zonule, pars plana,
anterior lens face, lens
equator and anterior vitreous
- Enables visualization
of morphology and
topography changes of
ACA structures associated
with lighting conditions,
drugs, indentation
gonioscopy and age
- Provides high-
resolution cross
sectional images of
anterior segment
to the iris-lens
- Is easy to operate
-Does not require
much collaboration
-Offers fast
-Allows exact
knowledge of image
-Can be used in
early post-operative
period and ocular
- Requires immersion
technique, although a
saline lled eye cap can be
adapted to the probe;
- May cause
Abrasion and infection
Potential anterior segment
Inadvertent indentation
- Is time-consuming
- Requires
Trained operator
Classically a more supine
Collaborative patient
-Does not provide
much detail of
structures posterior
to the iris
Table 2. Advantages and disadvantages of Ultrasound Biomicroscopy (UBM) and Anterior Segment OCT (AS-OCT).
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... UBM is a non-invasive technique which uses high-frequency ultrasound, typically 35-50 MHz, to visualise the anterior segment of the eye in detail [27]. Ultrasound waves have the ability to travel through the iris and ciliary body pigment epithelia, allowing the capture of high-resolution images of the anterior segment, particularly the ciliary body and ciliary processes, which are not otherwise visualised using AS-OCT [27,28]. UBM enables visualisation of morphological and topographical changes in the anterior chamber angle, but tolerance may be an issue, as it requires an immersion technique [28] (Table 2). ...
... Ultrasound waves have the ability to travel through the iris and ciliary body pigment epithelia, allowing the capture of high-resolution images of the anterior segment, particularly the ciliary body and ciliary processes, which are not otherwise visualised using AS-OCT [27,28]. UBM enables visualisation of morphological and topographical changes in the anterior chamber angle, but tolerance may be an issue, as it requires an immersion technique [28] (Table 2). ...
... Provides high-resolution visualisation of iris position [28] Enables visualisation of morphological and topographical changes in the anterior chamber angle [28] May cause discomfort, as it uses a probe that requires an immersion technique (a salinefilled eye cap can, however, be adapted to the probe) [28] May cause abrasion and infection, and potential anterior segment deformation [28] Patients must be in a more supine position and may require general or local anaesthetics [28] Time-consuming [28] Requires a trained operator [28] In vivo confocal microscopy ...
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Cystinosis, a rare autosomal recessive disease caused by intracellular cystine accumulation, occurs in an estimated 1/100,000–200,000 live births. Ocular non-nephropathic cystinosis is typically diagnosed during adulthood, when patients present with corneal crystal deposition and no systemic involvement. Due to the rarity of the condition, diagnosis is often delayed and can have a significant impact on the overall prognosis of the disease. Early diagnosis is therefore imperative to ensure successful treatment and improve quality of life, as most of its clinical manifestations can be prevented or delayed. Early detection strategies and practical approaches for the ocular management of cystinosis were discussed during the Ophthalmology Cystinosis Forum, a 1-day meeting held in Berlin, Germany during June 2017. Recommendations for early detection comprise ophthalmic assessment, including self- and clinician-assessed recording of photophobia, and visual acuity, slit-lamp examination and tonometry ophthalmic examinations. In vivo confocal microscopy and anterior segment optical coherence tomography were highlighted as valuable techniques in evaluating cystine crystals in the cornea, in vivo and non-invasively. The mainstay of ocular cystinosis treatment is the cystine-depleting aminothiol cysteamine. Indeed, early treatment with and strict adherence to cysteamine therapy has a considerable impact on the long-term prognosis of ocular cystinosis. In rare diseases such as ocular cystinosis, standardised guidelines and recommendations for detection, patient care and follow-up assessments are essential. Such guidelines provide a support tool for healthcare professionals caring for ocular cystinosis patients. Multidisciplinary teams (MDTs) are essential for delivering gold standard care and improving quality of life for patients and their families. This review paper highlights current early detection policies, clinical treatment strategies and practical approaches for the ocular management of cystinosis, including implementing a cystinosis MDT. Additionally, discussions of the Ophthalmology Cystinosis Forum held in 2017 are summarised. Funding Orphan Europe. Plain Language Summary Plain language summary available for this article.
... Изображения дренажных конструкций и устройств хорошо визуализируются с помощью ультразвуковой биомикроскопии Accutome (США), так как аппарат получает несколько изображений с разным фокусным расстоянием в быстрой серии снимков в одной и той же области с использованием автоматического точного фокуса. При завершении съемки прибор оценивает ряд сфокусированных кадров и далее у оператора есть возможность выбора альтернативных изображений сечения, обеспечивающих желаемый фокус и область угла передней камеры [11][12][13]. ...
Current methods of studying the angle of the anterior chamber (AAC) make it possible to visualize the structure and anatomical features of the AAC in various modes with high accuracy. In addition, visualization of the AAC in various ways helps to choose the treatment tactics for a patient with complicated cataract combined with lens subluxations. Aim. To compare current methods of visualization of the anterior chamber angle structures and evaluate their advantages and disadvantages in patients with different variants of its structure and features. Material and methods. The study involved 10 patients (10 eyes) who underwent a diagnostic examination using the Anterion OCT device (Heidelberg), the GS-1 electronic gonioscope (NIDEK-CO, LTD), and also performed ultrasound biomicroscopy using the Accutome device (USA) in the Orenburg branch of the S. Fyodorov Eye Microsurgery Federal State Institution. Results. After a detailed examination of the AAC before and after surgery using modern imaging techniques, the advantages and disadvantages of the abovementioned devices were revealed. Conclusion. The complex application of the presented methods of AAC visualization will allow a qualitative and detailed assessment of the advantages and disadvantages of the results of surgical treatment of glaucoma.
... Os primeiros dois tipos correspondem a ampolas não funcionantes. (3)(4)(5)(6) O grau de re etividade dos tecidos subconjuntivais e supra-esclerais tem sido comparado com as observações em microscopia confocal i i e com a funcionalidade da ampola de filtração. ...
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Trabalhar com som e luz para obter imagens é uma das facetas mais maravilhosas da Oftalmologia. Imagens belas, esclarecedoras, que possam ajudar o nosso semelhante é duplamente fantástico. Aqui partilhamos algumas, que esperamos assim possam contribuir e cuja existência deve um agradecimento a todos os colegas que nos confiaram os seus doentes e à sua colaboração...HPF ..."Este Atlas representa exatamente uma viagem de anos de trabalho em Imagiologia do segmento anterior. Representa a confiança de todos os que foram enviando casos para realização de exames, ilustra a dedicação e o tempo com que foram executados e interpretados e mostra a generosidade com que agora são partilhados." MSP
Imaging technologies, such as AS-OCT and UBM, are becoming essential tools for the better diagnosis and management of glaucoma. These devices provide precise visualisation and objective assessment of iridocorneal angle structures and the morphological analysis of filtering bleb that can help to reveal certain features and thereby predict the functional outcome before and after invasive and non-invasive surgery. Anterior segment imaging can explain the reasons whereby this procedure is unsuccessful.
Images captured in outer environment suffer from reduced scene visibility, reduced color contrast, and increased color fading. This may happen due to the presence of haze, fog, smoke, dust and noise present in the outer atmosphere. Haze is formed due to two basic processes, attenuation and air light. Attenuation diminishes the contrast of the image and air light makes the image to be whiter and hence the image captured is unclear. Haze removal or image dehazing is required in real-world weather conditions to obtain a fast and high-quality hazy free image which is used in various fields like satellite systems and aircraft systems. The intention of this review paper is to give a brief analysis on different haze removal techniques.
Glaucoma is one of the major abnormalities in the eye which leads to permanent vision loss over time if left untreated. Prolonged high level of intraocular pressure (IOP) causes optic nerve damage leading to glaucoma. Glaucoma can be detected by analyzing the characteristics of the optic nerve head (ONH) and retinal nerve fiber layer (RNFL). The quantitative analysis of the ocular details obtained by the imaging techniques can help in disease management. The algorithm used here automatically extracts clinical features such as anterior chamber width, iris endpoint width, chamber height, lens vault, angle opening distance, and trabecular iris angle from AS-OCT images to find the condition of eye, namely, the presence or absence of glaucoma.
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High resolution, high frequency, anterior segment ultrasound biomicroscopy (UBM) is a new technique capable of imaging the structures of the anterior segment at a resolution approaching 40 μm. It is now possible to image the structures surrounding the posterior chamber (posterior iris, ciliary body, zonules, peripheral lens), examination of which has been previously limited to histopathologic examination, making it ideally suited to elucidation of the mechanisms involved in the various disorders that produce the final common pathway known as angle-closure glaucoma.
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The purpose of this article is to review the plateau iris configuration demonstrating the importance of ultrasound biomicroscopy in the diagnosis. The possible non-pupillary block mechanism of angle-closure glaucoma and its management are also discussed.
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The anterior segment optical coherence tomography provides an objective method to assess the anterior segment of the eye, including the anatomy of the anterior chamber angle. This technology allows both qualitative and quantitative analyses of the angle and has shown potential in detecting and managing angle-closure glaucoma. In addition, it has a role in identifying pathology in some forms of secondary open-angle glaucoma and postsurgical management of glaucoma. Limitations of this technology include its cost and inability to visualize well structures posterior to the iris, such as the ciliary body. This paper focuses on potential benefits and limitations of anterior segment optical coherence tomography when compared with conventional gonioscopy and ultrasound biomicroscopy. Various clinical entities will be described to discuss its potential role in glaucoma practice.
Optical coherence tomography (OCT) is a cross-sectional, three-dimensional, high-resolution imaging modality that uses low coherence interferometry to achieve axial resolution in the range of 3-20 μm. Two OCT platforms have been developed: time domain (TD-OCT) and spectral (or Fourier) domain (SD/FD-OCT). Visante anterior segment OCT (Carl Zeiss Meditec) is a TD-OCT widely used for anterior segment imaging. The SD-OCT systems with both posterior and anterior segment imaging capabilities include the RTVue, iVue (Optovue), the Cirrus (Carl Zeiss Meditec), and the Spectralis (Heidelberg Engineering, Inc.). Each of the SD-OCTs has a wavelength in the range of 820-879 nm. Anterior segment OCT is a non-contact method providing high resolution tomographic cross-sectional imaging of anterior segment structures. Anterior segment OCT provides qualitative and quantitative assessment of the anterior segment structures important to the pathogenesis and the anatomical variations of glaucoma, and the approach to and success of treatment. We summarize the clinical applications of anterior segment OCT in glaucoma.
To assess the published literature pertaining to the association between anterior segment imaging and gonioscopy and to determine whether such imaging aids in the diagnosis of primary angle closure (PAC). Literature searches of the PubMed and Cochrane Library databases were last conducted on July 6, 2011. The searches yielded 371 unique citations. Members of the Ophthalmic Technology Assessment Committee Glaucoma Panel reviewed the titles and abstracts of these articles and selected 134 of possible clinical significance for further review. The panel reviewed the full text of these articles and identified 79 studies meeting the inclusion criteria, for which the panel methodologist assigned a level of evidence based on a standardized grading scheme adopted by the American Academy of Ophthalmology. Three, 70, and 6 studies were rated as providing level I, II, and III evidence, respectively. Quantitative and qualitative parameters defined from ultrasound biomicroscopy (UBM), anterior segment optical coherence tomography (OCT), Scheimpflug photography, and the scanning peripheral anterior chamber depth analyzer (SPAC) demonstrate a strong association with the results of gonioscopy. There is substantial variability in the type of information obtained from each imaging method. Imaging of structures posterior to the iris is possible only with UBM. Direct imaging of the anterior chamber angle (ACA) is possible using UBM and OCT. The ability to acquire OCT images in a completely dark environment allows greater sensitivity in detecting eyes with appositional angle closure. Noncontact imaging using OCT, Scheimpflug photography, or SPAC makes these methods more attractive for large-scale PAC screening than contact imaging using UBM. Although there is evidence suggesting that anterior segment imaging provides useful information in the evaluation of PAC, none of these imaging methods provides sufficient information about the ACA anatomy to be considered a substitute for gonioscopy. Longitudinal studies are needed to validate the diagnostic significance of the parameters measured by these instruments for prospectively identifying individuals at risk for PAC. Proprietary or commercial disclosure may be found after the references.
To describe the use of anterior segment optical coherence tomography (AS-OCT) in studying the dynamic changes of the anterior chamber angle by corneal indentation. In a prospective observational study, the anterior segments of 21 eyes were imaged using AS-OCT. After the initial scan, a second scan was executed on the same areas with a central corneal indentation. An evaluation of the reopening of the angle and its measurement were performed. With AS-OCT, the indirect signs were accurate enough to guide the diagnosis in all plateau iris confirmed by ultrabiomicroscopy. The angle widths were significantly increased after indentation. This method would appear to offer a convenient and rapid method of assessing the configuration of the anterior chamber; it may help during the routine clinical assessment and treatment of patients with narrow or closed angles, particularly when gonioscopy is difficult to interpret.
Primary angle-closure glaucoma (PACG) frequently leads to severe vision loss. Prevalence among older Asian populations is high and given global demographics, the number of persons with PACG will increase dramatically in the coming decades. Improvements in imaging of the anterior segment will help us to identify more of those with angle closure, and important clinical trials that are currently underway will provide important evidence to support screening and treatment approaches for PACG. In this manuscript, we intend to review the existing evidences, to introduce some important on-going studies on PACG and to share the experience and viewpoints of the authors.
To evaluate the relative safety and potential efficacy of high-intensity focused ultrasound cyclocoagulation by a miniaturized annular device containing six piezoceramic transducers in patients with refractory glaucoma. This was a three-center prospective interventional pilot study. Twelve eyes of 12 patients with refractory glaucoma were insonified using a ring-shaped probe containing six miniaturized high-frequency transducers operating at 21 MHz. Ultrasound biomicroscopy (UBM) and a complete ophthalmic examination were performed before the procedure and at 1 day, 1 week, 1 month, and 3 months after the procedure. Additional visits were performed 6 and 12 months after the procedure. Intraocular pressure was significantly reduced (P < 0.01) from a mean preoperative value of 37.9 ± 10.7 mm Hg to a mean postoperative value of 27.3 ± 12.4, 25.2 ± 11.3, 25.2 ± 7.7, 24.8 ± 9.8, and 26.3 ± 5.1 mm Hg at 1 day, 1 week, 1 month, 3 months, and 6 months, respectively, and to a mean value of 24.7 ± 8.5 at the last follow-up visit. No major intraoperative or postoperative complications occurred. Minor postoperative corneal complications developed in four patients with previous corneal abnormalities: superficial punctate keratitis (n = 3) and central superficial corneal ulceration (n = 1). UBM showed cystic involution of the ciliary body in 9 of the 12 eyes and a suprachoroidal fluid space in 8 of the 12 eyes. Ultrasonic circular cyclocoagulation using high-intensity focused ultrasound delivered by a circular miniaturized device containing six piezoceramic transducers seems to be an effective and well-tolerated method to reduce intraocular pressure in patients with refractory glaucoma.
Angle closure can recur following peripheral iridotomy in up to 58% of cases, due to plateau iris syndrome, lens disproportion or ciliary block. Ciliary block glaucoma is an important differential diagnosis of shallow anterior chamber, angle closure and high intraocular pressure, which may occur spontaneously or following laser or surgery. Some underlying mechanisms of ciliary block glaucoma remain poorly understood but lens-ciliary body apposition and anterior hyaloid changes with increased hydraulic resistance are major pathogenic factors. An understanding of the pathogenic factors facilitates early recognition of ciliary block glaucoma, and aids a logical sequence of intervention. We review the mechanisms of post-iridotomy angle closure and propose a stepwise treatment strategy for these conditions.
With recent advances in imaging techniques such as anterior segment optical coherence tomography and ultrasound biomicroscopy, there is a better understanding of nonpupil block mechanisms and novel risk factors contributing to the pathogenesis of angle closure glaucoma. Recent studies suggest that multiple anatomical and physiological factors interplay in the pathogenesis of angle closure glaucoma. The association of greater iris convexity, area and thickness with narrow angles could result in a more anterior bowing and crowding of the peripheral iris. Other novel anatomic parameters such as greater lens vault, smaller anterior chamber width, area and volume, independently increase the risk of having angle closure. Dynamic increase or lesser reduction in iris volume during dilation supports the theory of physiological predisposition to the disease process. Choroidal expansion has been demonstrated in untreated and treated, acute and chronic primary angle closure eyes. It remains unknown whether this finding is a cause or effect in this condition. With a wider availability of imaging tools and a better understanding of risk factors and mechanisms, clinicians maybe able to more accurately identify those at greater risk of developing angle closure disease and tailor their treatment according to the predominant factor(s) involved.