DOI:10.2214/AJR.04.1842
AJR 2006; 187:1061-1072
© American Roentgen Ray Society
Sonography of the Eye
Deepak G. Bedi1,
Daniel S. Gombos2,
Chaan S. Ng1 and
Sanjay Singh3
1 Department of Radiology, The University of Texas M. D. Anderson Cancer Center,
Box 57, 1515 Holcombe Blvd., Houston, TX 77030.
2 Department of Ophthalmology (Plastic Surgery), The University of Texas M. D.
Anderson Cancer Center, Houston, TX 77030.
3 Department of Radiology, Methodist Hospital, Houston, TX 77030.
Received December 3, 2004;
accepted after revision August 31, 2005.
Address correspondence to D. G. Bedi
(dbedi{at}di.mdacc.tmc.edu).
CME
This article is available for 1 CME credit. See
www.arrs.org
for more information.
Abstract
OBJECTIVE. The purpose of this study is to show how sonography can
reveal pathology of the eye and to highlight its usefulness as a simple and
cost-effective tool in investigating eye symptoms.
CONCLUSION. The cystic nature of the eye, its superficial location,
and high-frequency transducers make it possible to clearly show normal anatomy
and pathology such as tumors, retinal detachment, vitreous hemorrhage, foreign
bodies, and vascular malformations. Sonography is useful as a treatment
follow-up technique because it has no adverse effects. Sonography is well
tolerated by patients and relatively easy to perform for those familiar with
real-time sonography.
Keywords: eye sonography • ocular imaging • ocular melanoma • ocular sonography
Introduction
The superficial location of the eye, its cystic composition, and the advent
of high-frequency ultrasound make sonography ideal for imaging the eye
[1]. MRI is favored by
radiologists, so there are few reports on ocular sonography in the radiology
literature [2,
3]. Sonography is used more
commonly by ophthalmologists to evaluate the eye, particularly when direct
examination by slit-lamp and funduscopy is not sufficient. Detailed
cross-sectional anatomy of the entire globe is possible with conventional
sonographic equipment
[1-4];
anterior chamber visualization requires a dedicated sonographic biomicroscope
[5]. Color Doppler and A-mode
sonography [1,
6] are reported to be useful in
characterizing masses. The sonography examination is rapid and cost-efficient,
without the contraindications, such as pacemakers, that MRI has. Sonography
avoids the irradiation associated with CT and the need for sedation in
children [7]. Therefore, it can
be used repeatedly during treatment of tumors to assess response to
therapy.
Technique
Conventional gray-scale sonographic equipment (Elegra, Siemens Medical
Solutions; ATL, Philips Medical Systems) and 7.5-15-MHz transducers were used
by the radiology department, scanning through the closed eyelid
(Fig. 1A). The ophthalmology
department used a 10-MHz B-mode probe and an 8-10-MHz A-mode probe (Innovative
Imaging Systems), scanning through the open eye after paralyzing the blink
reflex (Fig. 1B). A dedicated
ocular sonographic biomicroscope, using frequencies up to 50 MHz
(Fig. 1C), was available for a
limited time.
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Fig. 1A —Technique for sonography of eye. Radiologists use compact
"hockey-stick" linear transducer with patient's eyelid closed.
Small amount of gel is sufficient for posterior eye anatomy; standoff pad or
abundant gel can be used for anterior chamber.
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In the illustrations shown here, the radiology transducers were linear and
the images are axial in a traditional anterior-to-posterior orientation.
Ophthalmology used sector transducers, and their images are also axial but
rotated in a left-to-right orientation to show the A-mode echo patterns. The
term "reflectivity" is used in some figure legends to describe
A-mode echo patterns and is similar to the term "echogenicity,"
but in addition describes amplitude of tissue interface reflection.
Normal Anatomy
The cornea, conjunctiva, anterior chamber, posterior chamber. and iris
(Figs. 2,
3A,
3B, and
3C) rarely require sonography
and are not well visualized with conventional sonography, but they are
excellently detailed with newer sonographic biomicroscopes. The lens is best
inspected directly, with no need for sonography. A mature cataract of the lens
may obscure the retina on funduscopy, necessitating sonography. The vitreous
body is gelatinous and anechoic, with loose attachments to the retina, and it
stabilizes the eyeball. The choroid is part of the uveal tract, which also
includes the ciliary body and iris, and is the site of many intraocular
tumors. The choroid has a rich vascular supply from the long and short
posterior ciliary arteries. Because the retina is pigmented, direct inspection
of the choroid by funduscopy is limited, and sonography plays an important
role in diagnosing choroidal melanoma and metastatic tumors. The retina and
choroid are sonographically perceived as one layer in the normal eye; the
sclera is a highly reflective outer layer.
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Fig. 2 —Axial cross-section of eye and diagrammatic representation of
pathology. C = cornea, A = anterior chamber, L = lens, V = vitreous body, CH =
choroid, CB = ciliary body, I = iris, R = retina, S = sclera, CRA = central
retinal artery, ON = optic nerve, PCA = posterior ciliary arteries.
Sonographic anatomic correlation is shown in Figures
3A,
3B, and
3C; some vascular structures
are seen only in Figures 3A,
3B,
3C,
16A, and
16B.
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Fig. 3A —Normal eye anatomy. Axial sonograms show normal anterior
chamber (A), lens (L), choroid (CH), ciliary body (CB), iris (I), and sclera
(S) in A and V = vitreous body (V) and optic nerve (ON) in
B.
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Fig. 3B —Normal eye anatomy. Axial sonograms show normal anterior
chamber (A), lens (L), choroid (CH), ciliary body (CB), iris (I), and sclera
(S) in A and V = vitreous body (V) and optic nerve (ON) in
B.
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Fig. 16A —2-year-old boy with rhabdomyosarcoma of extraocular muscle.
Hypoechoic, conical tumor (short arrows) is seen posterior to eye and
slightly superior to optic nerve (long black arrow). Retinal
detachment is also present (white arrow). Advantages of sonography in
this infant outweigh those of MRI because sedation was avoided with minimal
loss of anatomic information.
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Fig. 16B —2-year-old boy with rhabdomyosarcoma of extraocular muscle.
Color Doppler sonogram shows that despite tumor infiltration around optic
nerve (arrows), blood flow through central retinal artery (CRA) and
posterior short ciliary arteries (PCA) is intact.
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Fig. 4 —34-year-old man with cystic lesion of iris (arrow),
illustrated with use of standoff gel pad to visualize anterior eye anatomy. C
= cornea, A = anterior chamber, P = posterior chamber, V = vitreous body.
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Fig. 6A —52-year-old woman with choroidal melanoma. Typical
sonographic features include hypoechoic mass, lobular in shape, with marginal
retinal elevation (large arrow). Hyperechoic rim is combination of
elevated retina and peripheral blood vessels. Characteristic hypoechoic
echotexture is also seen in A-mode scan (graph at bottom), which
shows decreased reflectivity between two small arrows corresponding to margins
of mass, a feature that sometimes helps distinguish it from other types of
tumor (see Figs. 13,
14A,
14B, and
15).
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Fig. 13 —50-year-old woman with primary breast cancer metastasizing to
eye. Although flat hyperechoic tumor (long arrow) is morphologically
similar to lymphoma (Fig. 15)
or treated melanoma (Figs. 12A
and 12B), its surface is more
irregular, and A-mode sonography (tracing at bottom) shows high
reflectivity (short arrows).
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Fig. 14B —67-year-old man with metastatic adenocarcinoma from unknown
primary site. MR image shows subtle, isointense flat mass in nasal aspect of
right eye (arrow), which is best seen on this T1-weighted image;
T2-weighted images showed similar intensity for tumor and adjacent orbital
fat.
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Fig. 15 —38-year-old woman with lymphoma. Sonography depicts rather
flat mass of moderate echogenicity (long arrow). A-mode sonographic
tracing, taken through black-line axis, shows moderate reflectivity (short
arrows) that iSs greater than that of melanoma (low reflectivity) but
less than that of metastasis (high reflectivity).
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Fig. 6B —52-year-old woman with choroidal melanoma. Funduscopy shows
large dark melanoma (large arrows) with peripheral retinal elevation
(small arrows), which appears translucent yellow because red color of
underlying choroid, seen elsewhere, is lost.
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Fig. 7C —45-year-old woman with ciliary body melanoma. Ophthalmoscopy
shows dark tumor (arrows) partially obscuring normal "red
reflex" of retinochoroidal pigmentation seen through dilated pupil.
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Fig. 8 —62-year-old man with melanoma (arrow) arising from
ciliary body (C), which is small and buttonlike. Small melanoma of ciliary
body can be missed because of its small size and location if funduscopy is
performed without depressing sclera externally.
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The retina has a rich blood supply from the central retinal artery, which
is clearly seen on color Doppler sonography, as are the adjacent posterior
ciliary arteries that supply the choroid and the optic disk. The optic nerve
is visible sonographically as a hypoechoic band starting at the scleral zone
and extending posteriorly and medially.
Pathology
Lesions of the Iris
Cystic or solid lesions of the iris are difficult to show on conventional
equipment (Fig. 4) but are well
detailed on dedicated ultrasound biomicroscopic imaging
(Fig. 5). This equipment,
operating at 50 MHz or sometimes higher, has a resolution of 30 µm, far in
excess of CT or MRI.
Malignant Melanoma
Malignant melanoma (Figs.
6A,
6B,
7A,
7B,
7C, and
8) is the most common primary
intraocular tumor and occurs more often in the choroid than in the iris or
ciliary body. Iris melanomas can cause secondary glaucoma. Ciliary body
melanomas may cause changes in accommodation from lens displacement. Choroidal
tumors present with decreased visual acuity and visual field defects. A small
melanoma of the ciliary body (Fig.
8) can be missed if funduscopy is performed without depressing the
sclera externally. Melanomas of the eye are usually rounded, hypoechoic, and
very vascular. They can be complicated by retinal elevation and vitreous
hemorrhage (Figs. 9 and
10).
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Fig. 10 —Complications of melanoma in 69-year-old woman with
diminished brightness of vision. Vitreous hemorrhage, seen as low-level echoes
filling vitreous body (V), completely obscures direct view of tumor
(arrow) by funduscopy.
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Fig. 11 —Complications of melanoma in 42-year-old man with severe loss
of vision in one eye. Location of melanoma (large arrow) on and
adjacent to optic disk (small arrows) may prevent radiation treatment
and could necessitate enucleation of eye.
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Vitreous Hemorrhage
Vitreous hemorrhage spreads diffusely in the gelatinous vitreous, obscuring
the optic disk, and does not form a fluid meniscus unless the bleeding is in
the space around the vitreous. The causes of vitreous hemorrhage include
vitreous detachment, diabetic retinopathy, retinal microaneurysm, trauma, and
vascular tumors. The patient complains of "black rain" and has
reduced visual acuity. The hemorrhage is absorbed slowly, and the clinical
course depends on the exact cause. If choroid tumors are large or near the
optic disk (Fig. 11),
enucleation of the eye is sometimes necessary. However,
brachytherapy—that is, radiation plaques
[8] placed outside the sclera
adjacent to the tumor—is the preferred mode of treatment (Figs.
12A and
12B).
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Fig. 12A —55-year-old man with choroidal melanoma. Sonogram shows
melanoma (M) before brachytherapy (radiation plaque treatment). Melanoma is
biconvex, with slight elevation of retina (arrow) at one margin
because of serous fluid transudate.
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Fig. 12B —55-year-old man with choroidal melanoma. After radiation
plaque treatment, tumor (M) shows significant decrease in volume. Apical tumor
dimensions can be obtained using A-mode sonography (not shown).
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Metastasis and Lymphoma
Metastasis to the choroid is most common from the breast, lung, and unknown
primary sites (Figs. 13,
14A, and
14B). Metastatic tumors are
discoid in shape and hyperechoic compared with melanoma. A-mode sonography
shows the difference in echogenicity (also called "reflectivity"
in ophthalmology literature; see Figs.
6A,
6B, and
13) between melanomas and
metastases. Lymphoma can occur in isolation or as metastasis to the choroid or
the vitreous body (Fig.
15).
Rhabdomyosarcoma
Rhabdomyosarcoma is the most common primary malignancy of the orbital
cavity in children, presenting with proptosis, inflammation, and loss of
vision. A combination of radiation and chemotherapy makes a cure possible in
many cases. Sedation for repeated CT or MRI during follow-up was avoided in
the child shown in Figures 16A
and 16B by using
sonography.
Hemangioma
Hemangioma is the most common benign tumor of the orbital cavity and can be
capillary (in children) or cavernous (in adults, Figs.
17A,
17B, and
17C).
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Fig. 17A —37-year-old man with hemangioma of orbit. Nasal superior
location is common, as seen on this sonogram, which shows superior ophthalmic
vein (black arrow) draining hemangioma (white arrows).
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Fig. 17B —37-year-old man with hemangioma of orbit. IV
contrast-enhanced CT scan of orbits shows prominent draining vessels
(arrows) more clearly than sonogram, but repeated irradiation from CT
during follow-up was avoided by using sonography, which provided satisfactory
images and flow information.
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Fig. 17C —37-year-old man with hemangioma of orbit. Color Doppler
sonogram shows blood flow of mixed color (arrows), indicating some
turbulence in larger vessels of hemangioma in medial aspect of image. Draining
ophthalmic vein seen on gray-scale images and CT is not visible, presumably
because of low-velocity flow.
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Retinoblastoma
Retinoblastoma is the most common primary intraocular malignancy of
childhood [9] (Figs.
18A and
18B), often occurring before
the age of 3 years, and presenting with a white pupil (leukocoria) and
strabismus. Retinoblastoma is quite vascular and can invade the vitreous
body.
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Fig. 18A —1-year-old girl with retinoblastoma. Irregular shape of tumor
(short arrows) is hard to outline on this sonogram, but hyperechoic
calcific foci (long arrow) are characteristic of retinoblastoma.
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Microphthalmos and Coloboma
Microphthalmos and coloboma are congenital anomalies caused by incomplete
fusion of the optic cup in the sixth week of pregnancy. They cause a posterior
eyeball defect with a posterior orbital cyst and an abnormally short eye
(Figs. 19A and
19B).
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Fig. 19A —37-year-old man with microphthalmos and coloboma. Axial
left-to-right sonogram shows abnormally short length of eye (double
arrow), posterior defect or coloboma (single arrow), and cyst
(C) behind eye.
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Foreign Bodies
Foreign bodies can be metallic, plastic, or wood. The bodies usually lodge
in the conjunctiva or cornea, and the diagnosis is made by direct examination.
Occasionally penetrating through the cornea
(Fig. 20), metallic foreign
bodies may lodge anywhere up to the retina and can cause severe inflammation
and infection.
Asteroid Hyalosis
Asteroid hyalosis (Fig. 21)
is characterized by the presence of minute opacities due to calcific deposits
in the vitreous body, mainly in patients with diabetes and
hypercholesterolemia. It is usually unilateral and rarely bothersome to the
patient, but it can obscure the examiner's view of the fundus. If visual
acuity is affected, the deposits are removed by vitrectomy.
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Fig. 22 —58-year-old man with optic disk drusen. Sonography shows
characteristically hyperechoic spots at fundus (arrow) and is
particularly helpful in revealing drusen buried in optic nerve, which are
otherwise invisible on funduscopy.
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Optic Disk Drusen
Optic disk drusen (Fig. 22)
are calcified lobular bodies in the tissues of the optic disk and nerve that
are bilateral in most cases. Usually asymptomatic, optic disk drusen can cause
visual field defects if buried deep in the disk because of compressive atrophy
of nerve fibers.
Retinal Detachment
Retinal detachment (Fig.
23) is a separation of the neurosensory retina from the underlying
pigmented layer. This condition can be asymptomatic for a long time, then
presents with flashes of light, floaters, "black rain" (if there
is accompanying vitreous hemorrhage), a dark shadow, or loss of visual acuity,
depending on the exact location and severity of the detachment. The three
types are based on the cause: Rhegmatogenous detachment—that is,
associated with a retinal tear—is the most common type and is seen with
advancing age, a familial disposition, and associated myopia. Tractional
detachment originates in adjacent vitreous strands. Exudative detachment is
due to fluid, blood, or lipids behind the neurosensory retina and can be
associated with tumors of the choroid.
Conclusion
Sonography of the eye shows a variety of diseases with remarkable clarity.
The technique is more cost-efficient than other diagnostic techniques and is
well tolerated by the patient. We have experienced no limitations and have
received no complaints from patients. We do not advocate the routine use of
sonography in the asymptomatic eye, but it may serve as a useful extension of
the initial investigation of the symptomatic patient.
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Abstract
Introduction
