High resolution imaging of the equine cornea using the DUB

1
Original Article
High resolution imaging of the equine cornea using
the DUB®-SkinScanner v3.9
Lena E. Herbig1; Lothar Köhler2; J. Corinna Eule1
Small Animal Clinic, Freie Universität Berlin, Berlin, Germany; 2Faculty of Veterinary Medicine, Department for Large Animal Diseases with Clinic, Research Center for Veterinary
Medicine, Warsaw University of Life Sciences (SGGW), Poland
Keywords
Schlüsselwörter
Ultrasound, eye, biometry, keratitis, equine
Sonographie, Auge, Biometrie, Kornea, Pferd
Summary
Zusammenfassung
Objective: The aim was to describe the use of the DUB®-SkinScanner
v3.9 (taberna pro medicum GmbH, Lueneburg, Germany) for the examination of the equine cornea. Material and methods: Using the
DUB®-SkinScanner v3.9 various pathological corneal conditions were
pictured in the A- and B-mode at a frequency of 22 and/or 50 MHz in
nine eyes of eight horses. Scans were obtained from standing horses
or from horses under general anesthesia non-related to image acquisition. Results: The examination allowed real time imaging and measurement of the equine cornea in vivo. Compared to slit-lamp biomicroscopy additional information was obtained in seven of nine eyes
regarding the corneal thickness, in four of nine eyes regarding the
epithelium, in five of nine eyes regarding the stroma and in five of
nine eyes regarding the endothelium. Conclusion and clinical relevance: The DUB®-SkinScanner v3.9 is a valuable high-resolution imaging tool for the evaluation of the equine cornea under practice conditions. The image acquisition does not depend on corneal transparency and provides additional diagnostic information to the standard
slit-lamp biomicroscopy.
Ziel war, mit dem DUB®-SkinScanner v3.9 (taberna pro medicum
GmbH, Lüneburg, Deutschland) die Kornea des Pferdes darzustellen
und zu untersuchen. Material und Methoden: Neun Augen von acht
Pferden mit verschiedenen pathologischen Veränderungen der Kornea
wurden im A- und B-Mode mit einer Frequenz von 22 und/oder
50 MHz dargestellt. Die Bildgebung fand am stehenden Pferd oder
unter Vollnarkose statt, die nicht im Zusammenhang mit der Untersuchung der Hornhaut stand. Ergebnisse: Die Untersuchung ermöglichte eine Echtzeit-Bildgebung und Messungen an der Pferdehornhaut in vivo. Im Vergleich zur Spaltlampenuntersuchung ergaben sich
bei den neun untersuchten Augen zusätzliche Informationen bezüglich
der Korneadicke bei sieben Augen, bezüglich des Epithels bei vier
Augen und bezüglich des Stromas sowie des Endothels bei jeweils
fünf Augen. Schlussfolgerung und klinische Relevanz: Der
DUB®-SkinScanner v3.9 ist ein wertvolles Instrument für die hochauflösende Bildgebung, Messung und morphologische Beurteilung der
Hornhaut des Pferdes. Die Untersuchung lässt sich unabhängig von
der Transparenz der Hornhaut durchführen. Das Gerät kann im klinischen Alltag zur Bildgebung der Pferdehornhaut eingesetzt werden
und biometrische und diagnostische Daten liefern, die die Befunde der
Spaltlampenuntersuchung ergänzen.
Correspondence to
J. Corinna Eule
Small Animal Clinic
Freie Universität Berlin
Oertzenweg 19b
14163 Berlin
Germany
Email: [email protected]
Hochauflösende Darstellung der Hornhaut des Pferdes mit dem DUB®-SkinScanner v3.9
Tierärztl Prax 2016; 44 (G): ■■■
http://dx.doi.org/10.15653/TPG-160344
Received: March 21, 2016
Accepted after revision: May 31, 2016
Epub ahead of print: July 19, 2016
Introduction
Various ophthalmic conditions can lead to a loss of transparency
of the anterior segment and lens. Contrary to established examination techniques such as slit-lamp biomicroscopy (SLB) and ophthalmoscopy, the use of ultrasound is not dependent on the translucence of the optic media. In horses ocular ultrasonography using
frequencies between 5 and 10 MHz has been described as a non© Schattauer 2016
invasive, safe and practical tool for clinical examination, diagnosis
and treatment monitoring (13, 14, 18). Compared to diagnostic
ultrasound high frequency ultrasound (HF) and ultrasound biomicroscopy (UBM) have a higher resolution and a smaller tissue
penetration depth caused by a stronger absorption of the ultrasound waves (▶ Table 1) (16).
Fundamental properties of ultrasound such as attenuation, reflectivity and the speed of sound influence the imaging. In general
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L. E. Herbig et al.: High resolution imaging of the equine cornea
Table 1 Frequency ranges of diagnostic ultrasound, high frequency ultrasound (HF) and ultrasound biomicroscopy (UBM). Examples of different
ultrasound frequencies, their penetration depth and axial resolution are displayed (16).
Tab. 1 Frequenzbereiche von diagnostischem Ultraschall, hochfrequentem
Ultraschall (HF) und Ultraschallbiomikroskopie (UBM). Beispiele für die verschiedenen Ultraschallfrequenzen, ihre Eindringtiefe und ihre axiale Auflösung werden aufgeführt (16).
Classification Frequency
Frequency Penetration Axial resolrange (MHz) (MHz)
depth (mm) ution (µm)
Diagnostic
ultrasound
5–10
50–70
210
10
HF
UBM
7.5
35
158
10–40
22
8–10
72
40–100
50
3–4
31
the tissue reflectivity is composed by the specular reflection and,
when the target is comparable to or smaller than the wavelength of
sound, by backscatter (17). In the cornea the amount of backscatter is reported to increase with higher frequencies (20). Artifacts regularly encountered with diagnostic ultrasound may also
occur while using UBM. Shadowing, mostly due to air bubbles in
the coupling medium, improper positioning of the probe (not perpendicularly to the scanned area), motion, as well as compression
artifacts can reduce the image quality (16, 17).
In human ophthalmology HF and especially UBM are established in-vivo imaging techniques of the anterior segment at an almost microscopic level. Various applications have been described
such as anterior segment anatomy and diagnostic imaging of corneal pathologies (16, 19). The use of HF or UBM for anterior segment imaging, biometry and assessment of ocular clinical conditions has also been reported for cats, dogs and horses (1, 3, 5, 7–9).
The aim of this study was to examine nine equine eyes suffering
from different corneal pathologies with the DUB®-SkinScanner
v3.9 (taberna pro medicum GmbH, Lueneburg, Germany). The
additional information gained to previous SLB as well as the benefit for the therapy should be monitored.
Material and methods
All examined equines were privately owned and in a condition of
good general health. Seven warm blood horses and one pony presenting various pathological findings of the cornea were examined
(▶ Table 2). Owner consent was given for examination.
All animals were submitted to a thorough ophthalmic checkup
including SLB (SL-15, Kowa®, Tokyo, Japan) and direct ophthalmoscopy (Heine Beta® 200 Ophthalmoskop, Heine, Herrsching
Germany). The HF and/or UBM scans were either obtained from
the standing horse or during anesthesia. Six horses were manually
restrained and one horse required additional sedation (▶ Table 2).
Two horses were examined while undergoing general anesthesia.
Topical anesthesia of the cornea was performed in every case with
0.6% tetracainhydrochlorid eye drops (Ophtocain®-N, Dr. Winzer
Pharma GmbH, Berlin, Germany).
The DUB®-SkinScanner v3.9 was used to picture the cornea at a
high resolution in the A- and B-mode. The HF transducer works
at a frequency of 22 MHz (tissue depth 4 mm, axial resolution
74,6 µm) and the UBM transducer at a frequency of 50 MHz (tissue depth 4.15 mm, axial resolution 32.8 µm). A velocity of sound
of 1.640 m/s was chosen. Ten scan loops per second were stored.
For image acquisition the transducer was gently placed on the
cornea (▶ Fig. 1). Warm saline solution (NaCl 0.9% B. Braun®,
B. Braun Melsungen AG, Germany), the coupling medium, was
flushed into the silicone eye cap adapted to the shape of the equine
cornea. Two different caps, one without and one with a flange over
which the third eyelid could slip, were used. An example of a
healthy equine cornea pictured with both the HF and the UBM
transducer is shown in ▶ Fig. 2.
Table 2 Signalment, ocular abnormalities and examination conditions of the nine horses that were examined with the DUB®-SkinScanner v3.9.
Tab. 2 Signalement, Hornhautveränderungen und Untersuchungsbedingungen der neun mit dem DUB®-Skin Scanner v3.9 untersuchten Pferde
Breed
Gender
Holsteiner
mare
Holsteiner
Eye
Number of
the eye
Corneal condition
Probe
Restraint and
sedation
2
left
1
conjunctival flap
HF
manually restrained
mare
3
left
2
generalized stromal edema
UBM
manually restrained
Holsteiner
male
0.5
right
3
punctate keratitis
UBM
anesthesia
Holsteiner
mare
5
right
4
punctate keratitis
UBM and HF
manually restrained
German Riding Pony castrated male
9
left and right
5a and 5b
corneal erosion
UBM
manually restrained
Holsteiner
castrated male
6
right
6
ulcerative keratitis
UBM
manually restrained
Holsteiner
mare
4
right
7
ulcerative keratitis
HF
anesthesia
Thoroughbred
castrated male
18
left
8
stromal abscess
UBM
manually restrained
and sedated
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Age
(years)
© Schattauer 2016
L. E. Herbig et al.: High resolution imaging of the equine cornea
B-mode. The second line was positioned at the decreasing part of
the second prominent peak (A2) that stands for the Descemet’s
membrane and endothelium (DE). In the B-mode this corresponds to the back of the most reflective area of the DE (B2).
The information obtained during the examination of the cornea with the DUB®-SkinScanner v3.9 was compared to the results
of former SLB.
Results
Fig. 1 DUB®-SkinScanner v3.9 (taberna pro medicum GmbH, Lueneburg,
Germany) to which a silicone eye cap with a flange adapted to the equine
cornea is attached.
Abb. 1 DUB®-Skin Scanner v3.9 (taberna pro medicum GmbH, Lüneburg,
Deutschland) mit einem der Pferdehornhaut angepassten Silikonaufsatz
For measurements of the corneal thickness an internal caliper
was used. The first measurement line was set on the increasing
part of the first prominent peak (A1) in the A-mode. This corresponds to the front of the reflection of the epithelium (B1) in the
a
Fig. 2 a) High frequency ultrasound scan loop (22 MHz, A- and B-mode) of
a healthy cornea. In the A-mode the first prominent peak (A1) stands for the
corneal epithelium and the second peak (A2) corresponds to the Descemet’s
membrane and endothelium complex (DE). In the B-mode the epithelium
(B1) and the DE (B2) are both pictured as highly reflective arcs. One white or
black bar on the left side or on the bottom of the B-mode image corresponds
to 1 mm. b) Ultrasound biomicroscopy (UBM) scan loop (50 MHz, A- and
B-mode) of the same healthy cornea. The UBM image can be read almost in
the same way. Behind the first strong peak emitted by the epithelium,
multiple peaks are seen throughout the stroma (A3). In the B-mode the corneal stroma (B3), especially the anterior stroma, shows poor echogenicity
due to physiological backscatter.
© Schattauer 2016
Corneal thickness. The measured thickness of the corneas ranged
between 809 and 2055 μm. Corneas presenting erosion (n = 2) or
ulceration (n = 2) were thicker than the corneas of horses with
punctate keratitis (n = 2). The center of a corneal abscess had a
thickness of 1838 μm and in one horse with medically uncontrolled stromal edema a thickness of 2055 μm was measured
▶ (Fig. 3). Due to the ability of performing precise corneal
measurements with the DUB®-SkinScanner v3.9 in seven out of
nine eyes the information regarding the corneal thickness was
more accurate than with SLB (▶ Table 3).
Epithelium. In three examined eyes the first peak normally observed in the A-mode in the area of the epithelium was very small.
In the B-mode the arc corresponding to the epithelium was less reflective and discontinuous (▶ Fig. 4). In two horses with ulcerative
keratitis in the area of the stromal defect the anterior surface of the
b
Abb. 2 a) Hochfrequenz-Ultraschall(HF)-Scan (22 MHz, A- und B-Mode) einer gesunden Hornhaut. Im A-Mode steht die erste prominente Zacke (A1)
für das Hornhautepithel und die zweite Zacke (A2) für die Descemet‘sche
Membran und das Endothel (DE). Im B-Mode stellen sich das Epithel (B1)
und DE (B2) als hochreflektierende Bögen dar. Ein weißer oder schwarzer
Balken auf der linken Seite und auf der Unterseite des B-Mode-Bildes entspricht 1 mm. b) Ultraschallbiomikroskopie(UBM)-Scan (50 MHz, A- und
B-Mode) der gleichen gesunden Hornhaut. Das UBM-Bild kann fast in der
gleichen Weise interpretiert werden. Hinter der ersten durch das Epithel verursachten hohen Zacke sind mehrere Ausschläge im gesamten Stroma (A3)
zu erkennen. Im B-Mode fällt eine geringe Echogenität des Hornhautstromas
(B3), insbesondere des vorderen Stromas, auf, die durch physiologische
Rückstreuung entsteht.
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L. E. Herbig et al.: High resolution imaging of the equine cornea
Number of
the eye
Corneal condition
Corneal
thickness
Epithelium
Stroma
Endothelium
1
conjunctival flap
+
–
+
+
2
generalized stromal
edema
+
+
+
+
3
punctate keratitis
–
–
–
–
4
punctate keratitis
–
–
–
–
5a
corneal erosion
+
–
–
–
5b
corneal erosion
+
–
–
–
6
ulcerative keratitis
+
+
+
+
7
ulcerative keratitis
+
+
+
+
8
stromal abscess
+
+
+
+
Table 3
Information gained during corneal examination
with the DUB®- SkinScanner v3.9 compared to
information provided by slit-lamp biomicroscopy.
The plus (+) indicates that supplement information was gained and the minus (–) that no additional findings could be obtained using the
DUB®-SkinScanner v3.9.
Tab. 3
Vergleich zwischen den Ergebnissen der Hornhautuntersuchung mit dem DUB®-SkinScanner
v3.9 bzw. der Spaltlampen-Biomikroskopie. Das
Plus (+) gibt an, dass durch den DUB®-SkinScanner v3.9 zusätzliche Informationen gewonnen
wurden, das Minus (–), dass das Gerät keine weiteren Befunde lieferte.
cornea generated peaks of small amplitude in the A-mode and
echoes of varying intensity in the B-mode (▶ Fig. 5). Compared to
SLB additional information was obtained in four of nine eyes regarding the structure and thickness of the epithelium (▶ Table 3).
Stroma. In all the examined eyes changes of the stroma, especially in the anterior and mid part, were seen both in the A- and
B-mode. In the A-mode an increase of the amount and amplitude
of the peaks was observed. In the B-mode a higher reflectivity was
pictured. The amplitude of the peaks as well as the intensity of the
reflection was variable between the examined eyes. In five of nine
eyes supplement information regarding the stroma was gained
with the DUB®-SkinScanner v3.9. Here a clear advantage of the device was the ability to picture the complete stroma even if opacities
obscured the SLB (▶ Table 3).
Endothelium. In two eyes, one with chronic generalized stromal edema and one with ulcerative keratitis, the scans revealed
changes of the morphology in the area of the DE. Adjacent to the
DE in the anterior eye chamber of both patients irregular, echogenic structures were pictured (▶ Fig. 6). In five of nine eyes additional information regarding the structure and the continuity
of the endothelium was achieved with the SkinScanner v3.9.
(▶ Table 3).
Corneal vascularization. In four eyes neovascularization of the
cornea was observed. The vessels were pictured in two eyes (cornea with conjunctival flap and ulcerative keratitis). In both eyes
the A-mode revealed various small peaks throughout the stroma.
In the B-mode multiple round and oval anechoic inclusions were
found in the anterior and mid stroma (▶ Fig. 7).
Fig. 3 UBM scan loop (50 MHz, A- and B-mode) of a generalized stromal
edema. A corneal thickness of 2055 µm was measured.
Abb. 3 UBM-Scan (50 MHz, A- und B-Mode) eines generalisierten Stromaödems. Die gemessene Hornhautdicke betrug 2055 µm.
Fig. 4 UBM scan loop (50 MHz, A- and B-mode) of a cornea with ulcerative
keratitis. The area of the epithelium (yellow line) shows only a small peak in
the A-mode and in the B-mode the epithelium displays a low echogenicity.
Abb. 4 UBM-Scan (50 MHz, A- und B-Mode) einer Hornhaut mit ulzerativer
Keratitis. Der Bereich des Epithels (gelbe Linie) stellt sich im A-Mode als eine
kleine Spitze dar und im B-Mode ist das Epithel von geringer Echogenität.
Tierärztliche Praxis Großtiere 5/2016
© Schattauer 2016
L. E. Herbig et al.: High resolution imaging of the equine cornea
Fig. 5 HF scan loop (22 MHz, A- and B-mode) of a cornea with ulcerative
keratitis. The anterior surface of the cornea (yellow line) generates peaks of
small amplitude in the A-mode and echoes of moderate echogenicity in the
B-mode.
Abb. 5 HF-Scan (22 MHz, A- und B-Mode) einer Hornhaut mit ulzerativer
Keratitis. Die Oberfläche der Hornhaut (gelbe Linie) erzeugt im A-Mode Ausschläge geringer Amplitude und im B-Mode Reflexionen von mittlerer Echogenität.
Fig. 6 UBM scan loop (50 MHz, A- and B-mode) of a cornea with chronic
generalized stromal edema. The arrow points out the irregular echogenic
structures that were pictured in the anterior eye chamber.
Abb. 6 UBM-Scan (50 MHz, A- und B-Mode) einer Hornhaut mit chronischem generalisiertem Stromaödem. Der Pfeil zeigt auf die unregelmäßigen
echogenen Strukturen, die in der vorderen Augenkammer abgebildet wurden.
Artifacts. In scans of four eyes artifacts were seen. A large, irregular, echogenic structure was pictured in the lower part of the
B-scan in front of the endothelium of one eye (▶ Fig. 8). In the
anterior eye chamber of one horse an echoic, large and irregularly
shaped structure was seen. In two eyes small echogenic structures
were seen in the B-mode scan in front of the cornea (▶ Fig. 9
[circle]).
Discussion
The aim of this study was to describe the use and the benefits of
the DUB®-SkinScanner v3.9 for the clinical examination of the
equine cornea. The obtained A- and B-mode scans allowed invivo, high-resolution, real time imaging and biometry the cornea.
The examination was not dependent on transparency of the cornea and procured reliable and accurate additional information to
the standard slit lamp examination.
In veterinary ophthalmology image acquisition and diagnosis
with HF and UBM has been described as a valuable technique that
is not dependent on the transparency of the ocular structures. Reported applications are the biometry of the anterior segment such
as corneal thickness measurements, the assessment of the iridocorneal angle, as well as the evaluation of various conditions of the
anterior segment (4, 5, 7–10, 15). To our knowledge only one study
reported the use of HF for the examination of a slowly growing
mass on the surface of an equine cornea in a single patient at a frequency of 20 MHz (3).
With the DUB®-SkinScanner v3.9 various observations were
made during the examination of nine eyes presenting different
© Schattauer 2016
Fig. 7 UBM scan loop (50 MHz, A- and B-mode) of a cornea with ulcerative
keratitis. The area of neovascularization is pictured. In the A-mode various
small peaks throughout the stroma (area between the yellow and red line)
and in the B-mode multiple round and oval anechoic inclusions are seen especially in the anterior and mid stroma.
Abb. 7 UBM-Scan (50 MHz, A- und B-Mode) einer Hornhaut mit ulzerativer Keratitis. Der Bereich mit Neovaskularisation ist abgebildet. Im A-Mode
sind verschiedene kleine Ausschläge im gesamten Stroma (Bereich zwischen
der gelben und der roten Linie) zu erkennen. Im B-Mode stellen sich vor allem im vorderen und mittleren Stroma mehrere runde und ovale anechogene
Einschlüsse dar.
corneal conditions. The corneal thickness was remarkably increased in all eyes presenting a corneal erosion, ulceration or abscess. The thickening is most likely due to the corneal swelling
caused by a higher stromal hydration caused by a discontinuity or
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L. E. Herbig et al.: High resolution imaging of the equine cornea
Fig. 8 UBM scan loop (50 MHz, A- and B-mode) of a corneal erosion. On
the bottom of the B-mode scan the arrow points out a large echogenic structure that corresponds to the third eyelid.
Abb. 8 UBM-Scan (50 MHz, A- und B-Mode) einer Hornhauterosion. Im
B-Mode zeigt der Pfeil auf eine große echogene Struktur, die dem dritten
Augenlid entspricht.
destruction of the limiting layers (epi- and endothelium) and their
dehydration mechanisms (11, 12). The neovascularization of the
cornea that was seen in some eyes might have caused punctual
edema resulting in an additional increase in thickness (6). The
thickening was also seen during previous SLB. Here the increase in
thickness of the corneal section was, if not obscured by corneal
Fig. 9 UBM scan loop (50 MHz, A- and B-mode) of a corneal erosion. The
corneal stroma (area between the yellow and the red line) especially the anterior and mid stroma emits various peaks in the A-mode. In the B-mode a
higher reflectivity of this area is seen. The echogenic structures pictured on
the bottom of the B-scan are artifacts (circle).
Abb. 9 UBM-Scan (50 MHz, A- und B-Mode) einer Hornhauterosion. Im
A-Mode generiert das Stroma (Bereich zwischen der gelben und der roten Linie), insbesondere das vordere und mittlere Hornhautstroma, mehrere Ausschläge. Im B-Mode zeigt sich eine höhere Reflektivität in diesem Bereich.
Die echogenen Strukturen im unteren Bereich des B-Scans sind Artefakte
(Kreis).
Tierärztliche Praxis Großtiere 5/2016
edema and opacity, estimated. With the DUB®-SkinScanner v3.9
the increase in thickness was objectified by precise measurements.
It was possible to picture epithelial thinning, loss, discontinuity
and restructuration with the DUB®-SkinScanner v3.9. In eyes with
an epithelial defect in the area of the anterior surface of the cornea
echoes of varying intensity were seen. These were most likely generated by necrotic tissue, cellular infiltrates and fluid. With the
DUB®-SkinScanner, especially if the external surface of the cornea
was strongly damaged and opaque, supplement information was
gained regarding for example the thickness and structure of the
epithelium and of the stroma behind. In these cases the examination with SLB was limited. A loss of intensity of the reflected light
and an irregular image were seen in the area of the defect and a
precise examination of the structures behind the defect was not
possible.
In all scans the stroma showed a higher amount of peaks in the
A-mode and an increase of echogenicity in the B-mode. In humans an increase of reflectivity of the stroma was found when
structural changes in the microanatomy, caused for example by
edema, the presence of blood vessels or scarring of the tissue were
present (2, 16, 17, 21). Previous examinations with a 20 MHz
ultrasound device of one diseased equine and one feline cornea
also showed that structural changes of the corneal stroma resulted
in an increase of echogenicity (3).
Various inflammatory and healing processes were pictured
with the DUB®-SkinScanner v3.9. Leucocyte migration, the presence of edema fluid, cellular debris, scarred tissue and small blood
vessels might have altered the microanatomy of the stroma and
therefore have lead to an increase and variability of reflectivity. In
eyes with a mostly clear cornea the stroma was examined using
SLB. However if a part of the cornea was covered by a conjunctival
flap or if the stroma was opaque, SLB of the stroma was impeded
and information about deeper structures of the cornea were not
gained. With the DUB®-SkinScanner v3.9 an increase of echogenicity was seen in areas with changes in the stromal microanatomy. The rest of the cornea was pictured in detail and all structures could be examined.
With the DUB®-SkinScanner v3.9 structural changes of the
Descemet’s membrane and the endothelium (DE) were pictured.
In the anterior eye chamber adjacent to the DE ill-defined echogenic structures, which seem to correspond to aggregations of cellular and/or organic material, were pictured. These echogenic
structures were more or less attached to the DE and could be interpreted as endothelial precipitates. During previous SLB of eyes
with opaque corneal media it was not possible to examine the DE
in detail neither was it possible to picture structures behind the
DE.
The examination of the eye with a conjunctival flap and of the
vascularized area of an ulcerated cornea revealed small round anechoic patterns in the flap and in the stroma. These are most likely
corresponding to the lumen of small blood vessels seen during the
previous SLB. However this finding needs to be clarified by the use
of a device with a Doppler function in the future.
© Schattauer 2016
L. E. Herbig et al.: High resolution imaging of the equine cornea
Clinical relevance
The DUB®-SkinScanner v3.9 is a good and financially affordable tool
to picture and measure the equine cornea. Especially if a tremendous
edema and/or inflammatory infiltrate impaires both the clinical examination and slit-lamp biomicroscopy additional clinical information can be achieved with this device. The depth and extent of a
lesion can be evaluated and an appropriate medical and/or surgical
approach can be chosen. The ability of performing precise measurements makes it possible to objectify structural changes. During follow-up examinations the data can be compared to previously obtained findings and a close and objective monitoring of the impact of
therapy is possible. Additionally with the obtained scans the owners
are able to visualize and understand the corneal pathologies and a
positive influence on the compliance is noticed.
Some artifacts were encountered. The small, echogenic structures that were seen in front of the cornea of two eyes most likely
correspond to small air bubbles in the coupling medium. The
echogenic structure pictured in front of the cornea corresponds to
the third eyelid and the structure in the anterior eye chamber corresponds to the corpora nigra of the right eye. The artifacts did not
impair image quality and interpretation.
The examination with the DUB®-SkinScanner v3.9 was well tolerated by standing and manually restrained horses. Only one horse
required light sedation. To prevent the occurrence of motion and
compression artifacts the silicone eye caps were adapted to the
curvature of the equine cornea and local anesthesia of the cornea
was performed. The device is small and easy to handle and can be
used for examinations under practice conditions. Due to the limited penetration depth of HF and UBM devices we additionally
recommend scanning the affected eye and annexes with a lower
frequency ultrasound device.
In conclusion it can be said that the DUB®-SkinScanner v3.9
allows the in-vivo, high-resolution, real time imaging and biometry of the equine cornea. Additional information to standard
SLB can be gained. Changes in the thickness of the cornea are objectified by precise measurements. Image acquisition is not dependent on optical transparency and the full thickness of the cornea can be assessed even when the cornea is opaque or covered by
a conjunctival flap. Therefore the morphology of structures behind
opacities such as the DE can be examined. Overall it is a precise
and valuable device for corneal biometry and an adjunct to standard SLB in clinical diagnosis.
Conflict of interest
The authors declare not to have any conflict of interest.
© Schattauer 2016
References
1. Aubin ML, Powell CC, Gionfriddo JR, Fails AD. Ultrasound biomicroscopy
of the feline anterior segment. Vet Ophthalmol 2003; 6 (1): 15–17.
2. Avitabile T, Russo V, Ghirlanda R, Castiglione F, Marino A, Reibaldi A.
Corneal oedemas: diagnosis and surgical planning with ultrasound biomicroscopy. Ophthalmologica 1998; 212 (Suppl. 1): 13–16.
3. Bentley E, Miller PE, Diehl KA. Use of high-resolution ultrasound as a
diagnostic tool in veterinary ophthalmology. J Am Vet Med Assoc 2003;
223 (11): 1617–1622.
4. Bentley E, Miller PE, Diehl KA. Evaluation of intra- and interobserver reliability and image reproducibility to assess usefulness of high-resolution
ultrasonography for measurement of anterior segment structures of canine
eyes. Am J Vet Res 2005; 66 (10): 1775–1779.
5. Cronau M, Gerhards H. Hochauflösende Sonographie am Auge des Pferdes. Pferdeheilk 2004; 20: 321–326.
6. Cursiefen C, Seitz B, Dana MR, Streilein JW. Angiogenesis and lymphangiogenesis in the cornea. Pathogenesis, clinical implications and treatment
options. Ophthalmologe 2003; 100 (4): 292–299.
7. Herbig LE, Eule JC. Central corneal thickness measurements and ultrasonographic study of the growing equine eye. Vet Ophthalmol 2015; 18 (6):
462–471.
8. Hoffmann I, Köstlin R. Die sonographische Untersuchung des vorderen
Augenabschnittes beim Kleintier. Teil 1: Untersuchungstechnik und echographische Normalbefunde. Tierärztl Prax 2004; 32 (3): 175–179.
9. Hoffmann I, Schäffer E, Reese S, Köstlin R. Die sonographische Untersuchung des vorderen Augenabschnittes beim Kleintier. Teil 2: Pathologische
Befunde. Tierärztl Prax 2004; 32 (4): 238–246.
10. Kawata M, Hasegawa T. Evaluation of the distance between Schwalbe‘s line
and the anterior lens capsule as a parameter for the correction of ultrasound biomicroscopic values of the canine iridocorneal angle. Vet Ophthalmol 2013; 16 (3): 169–174.
11. Maurice DM, Giardini AA. Swelling of the cornea in vivo after the destruction of its limiting layers. Br J Ophthalmol 1951; 35 (12): 791–797.
12. Meek KM, Leonard DW, Connon CJ, Dennis S, Khan S. Transparency,
swelling and scarring in the corneal stroma. Eye 2003; 17 (8): 927–936.
13. Mettenleiter EM. Sonographic diagnosis (B-mode technique) for the eyes
in horses. 1. Methods and normal findings. Tierärztl Prax 1995; 23 (5):
481–488.
14. Mettenleiter EM. Sonographic diagnosis (B-mode techniques) for the eyes
of horses. 2. Pathological cases. Tierärztl Prax 1995; 23 (6): 588–595.
15. Moodie KL, Hashizume N, Houston DL, Hoopes PJ, Demidenko E,
Trembly BS, et al. Postnatal development of corneal curvature and thickness in the cat. Vet Ophthalmol 2001; 4 (4): 267–272.
16. Pavlin CJ, Foster FS. Ultrasound Biomicroscopy of the Eye. New York:
Springer 1995; 214.
17. Pavlin CJ, Harasiewicz K, Sherar MD, Foster FS. Clinical use of ultrasound
biomicroscopy. Ophthalmology 1991; 98 (3): 287–295.
18. Scotty NC. Ocular ultrasonography in horses. Clin Tech Equine Pract 2005;
4 (1): 106–113.
19. Silverman RH. High-resolution ultrasound imaging of the eye – a review.
Clin Experiment Ophthalmol 2009; 37 (1): 54–67.
20. Ye SG, Harasiewicz KA, Pavlin CJ, Foster FS. Ultrasound characterization
of normal ocular tissue in the frequency range from 50 MHz to 100 MHz.
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
1995; 42 (1): 8–14.
21. Zhou SY, Wang CX, Cai XY, Huang D, Liu YZ. Optical coherence tomography and ultrasound biomicroscopy imaging of opaque corneas. Cornea 2013; 32 (4): e25–30.
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