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Ocular ultrasound
Clinical Radiology (1996) 51, 533-544
Pictorial Review Ocular Ultrasound J. A. FIELDING
Department of Radiology, Royal Shrewsbury Hospital, Shropshire, UK
The anatomy of the eye is faithfully reproduced by high frequency ultrasound. When the light-conducting media are opacified by cataract, haemorrhage or membranes preventing clinical examination by ophthalmoscopy, ultrasonography is the most practicable and rapid method of obtaining images of the posterior segment. Contact scanning is a simple technique which requires careful application, releasing information for diagnosis and pre-operative planning, and providing an accurate depiction of the internal structure. The 2-D images assessed in real-time enable the operator to construct mentally a 3-D concept of intraocular pathological processes. Ophthalmic ultrasonography has long been the province of ophthalmologists, often using dedicated equipment. However with the advent of high resolution general purpose scanners with small parts probes, radiologists are becoming increasingly involved in this field [!]. The globe is the dominant structure in the anterior orbit, and its cystic structure and superficial position make it ideal for ultrasound examination (Fig. 1). To understand the pathological appearances of the detached retina,~choroid and vitreous, a clear knowledge of the anatomy and fixed anchoring points of the inner and middle coats and vitreous is required (Fig. 2). Ultras(ound is the quickest and simplest method of imagin'g the eye, and at energy levels used for diagnostic purposes, no known adverse effects have been demonstrated [2]. Opaque media caused by cataract, haemorrhage or vitreous membranes conceal the intraocular contents from clinical examination, making ultrasonography the most useful examination for assessment and prior to vitrectomy [3,4]. Although computed tomography [5] and magnetic resonance imaging are invaluable in many orbital conditions, they cannot scan in real-time, lack spatial resolution, and have considerable limitations when imaging the vitreous and retina, where ultrasound contributes more to tissue diagnosis. Dynamic scanning is important, and with increasing experience the examiner is able to study characteristics of the motion and topography of pathological intraocular conditions [6], enabling differentiation of retinal detachment and vitreous membrane, or tumour and haemorrhage [7]. Colour Doppler imaging is a recent development, facilitating the study of ocular and orbital blood flow. Colour coded Doppler information is superimposed upon a conventional B scan image, so that structure and blood flow are seen simultaneously, aiding identification of small orbital vessels, direction of flow, and calculation of flow velocity in vascular disease and tumours [8]. Correspondence to: Dr J.A. Fielding, Department of Radiology, Royal Shrewsbury Hospital, Shropshire SY3 8XG, UK. © 1996 The Royal Collegeof Radiologists.
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The image resolution of current ultrasound scanners has brought eye scanning within the scope of departments possessing a short-focus 7.5 or 10 MHz real-time, small parts probe [9]. A built-in stand-off facility improves image quality of the anterior structures, but is not necessary for the posterior segment. Sector scanning is carried out with the patient lying supine, when the pull of gravity is exerted in the direction of the optic axis. This enables a detached vitreous still suspended from the vitreous base, or the sedimentation of blood, to be assessed with the patient in a relaxed and supported state. However, some operators prefer the patient to be scanned in the sitting position. The simplest way of examining the eye is contact scanning, when the probe is placed directly on the closed eyelid, with an intervening sterile coupling gel. The aim is to image the globe while static, and during rapid eye movement with the patient deviating the eyes to the right and left side. Mobility of the pathological vitreous and retina is observed during dynamic scanning, together with vitreoretinal adhesions, and following an ocular excursion, after-movements may continue for approximately a second [6]. The gel moves as a complete body, but the detached retina undulates as a membrane, unless fixed by fibrosis. Choroidal tumours are solid, and their attachment to the ocular wall is apparent, whereas vitreous, retrohyaloid or sub-retinal haemorrhage may swirl and sediment during eye movements. When vitreoretinal microsurgical techniques are being considered, information provided by these methods of scanning about the structure and mobility of the ocular contents is of great importance when assessing surgical approach and prognosis.
Indications The indications for eye scanning are as follows: (a) opaque light-conducting media, precluding ophthalmoscopy; (b) suspected intra-ocular tumour solid lesions are readily identified, positioned and measured by ultrasound; (c) differentiation of serious and solid retinal detachment. Detachments may conceal a tumour - the subretinal area is clearly demonstrated by ultrasound; (d) examination of the vitreous; (e) localization of foreign bodies; (f) ocular measurements (biometry - needs calibrated equipment); (g) proptosis; (h) colour Doppler imaging in ocular and orbital vascular disease and tumours. Patients with opaque, light-conducting media are the majority of referrals, especially those with cataracts and
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Fig. 1 - Normal eye showing iris (small arrow), and posterior lens surface (arrow). Horizontal scan.
haemorrhages. It is not necessary to scan every patient with a cataract, but if there are concurrent symptoms, for example, inflammation, pain, rapidly worsening vision, or the development of glaucoma, then a scan must be performed to determine any co-existent pathology. Prior to vitreoretinal surgery ultrasound assessment of the globe is mandatory [4]. Information required includes: (a) the state of the vitreous; (b) the position and extent of any intraocular lesion; (c) the condition of the retina, and particularly, the macula; (d) the mobility of the contents of the globe, which influences operability; (e) the relation between the vitreous and retina, mapping vitreoretinal adhesions.
Fig. 3 - Subcapsular cataract. Horizontal scan.
PATHOLOGY A range of the most commonly encountered and important clinical entities is described and illustrated. Lens
The lens contents are normally ar~echoic but immature cataract forms lenticular opacities seen as reflective areas. Subcapsular cataract leaves a deposition of reflective material outlining the lens capsule. A mature cataract causes a totally reflective cortex resulting in a very dense lens on scanning (Fig. 3). A plastic lens implant is frequently inserted after cataract extraction. It is important to be aware of the presence of these as they cause a dense artefact in the vitreous, so scanning must be carried out in a plane which avoids the implant (Fig. 4). Retina and Choroid Retinal Detachment
Fig. 2
Section of eye.
There are two main types of retinal detachment: rhegmatogenous (arising from a retinal break or tear), and non-rhegmatogenous (or secondary detachment): Retinal breaks which result in detachment are caused by weakness in the peripheral retina from degeneration (Fig. 5), for example lattice degeneration in myopes [10] and vitreoretinal traction from a detached vitreous [11]. The forms of non-rhegmatogenous retinal detachment are tractional and exudative [12,13]. Tractional © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533-544.
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Fig. 4 - I m p l a n t artefact (arrow). Horizontal scan. Fig. 6 Classic V-shaped retinal detachment and collapsed vitreous (arrow). Horizontal scan.
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detachment occurs when contracting vitreoretinal membranes pull the sensory retina away from the pigment epithelium, resulting in angular lesions. Diabetes and penetrating trauma are the main causes. Exudative detachment occurs when subretinal fluid from the choroid enters the subretinal space in inflammation (uveal effusion syndrome) or t u m o u r . Firm attachments of the retina exist at the ora serrata and the optic nerve head, ensuring that detachment does not extend beyond these sites (Fig. 6). A classical, total detachment, therefore, shows a funnel-shaped appearance, and in a recent detachment, dynamic scanning reveals an undulating, sinuous or whiplash motion of the retinal leaves. A minority of retinal detachments remain stationary for some years, but if untreated most detachments become total and progressively immobile, because of the development of epiretinal fibrosis. The retina contracts to form a taut membrane, stretched between the optic disc and ora serrata (Fig. 2b). Choroidal Detachment
Fig, 5 - Retinal tear (small arrow) and detachment (arrow). Horizontal scan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
Choroidal detachment is caused by fluid in the suprachoroidal space, limited by the choroidal anchoring points - anteriorly at the scleral spur, posteriorly near the exit foramina of the vortex veins. A complete detachment, therefore, appears on scanning as convex indentations of the globe. If the vortex veins are absent or avulsed, the detachment may extend to the optic disc. Choroidal detachment may occur with retinal detachment in exudative conditions, but also with rhegmatogenous detachment [6]. Ultrasound may reveal choroidal tumour (melanoma, secondary deposit or retinoblastoma) as the cause of an exudative detachment; but the aetiology also includes endogenous uveitis (Fig. 7) and infection. Subchoroidal haemorrhage is a serious
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Fig. 7
Choroiditis. Colour Doppler scan.
post-surgical complication but it also occasionally occurs spontaneously (Fig. 8). Vitreous
The vitreous gel is transonic, but with careful adjustment of the scanner's sensitivity, dynamic scanning shows some undulations of the posterior hyaloid surface, with eye movements. The vitreous is imaged more easily if occupied, or surrounded by blood or other pathological material (Figs 9 & 10), and its motion is that of an elastic body.
Fig. 9 - Vitreous haemorrhage. Horizontal scan.
Vitreous Haemorrhage Small haemorrhages may be difficult to demonstrate and usually resolve after an interval. Larger bleeds are seen more easily as low density echoes, which may persist with development of fibrinous membranes (Fig. 11). Fibrosis or organization is an unusual sequel to vitreous haemorrhage, and is usually associated with trauma or diabetes and vasculitis [14], resulting in the formation of epiretinal membranes (proliferative vitreoretinopathy). Contracture of these membranes with
Fig. 8 - Subchoroidal haemorrhage. Colour Doppler scan.
Fig. 10 - Subvitreal haemorrhage. Vertical scan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544
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Fig. 11 - F i b r i n o n s m e m b r a n e s w i t h i n vitreous. H o r i z o n t a l scan.
Fig. 13 - A s t e r o i d hyalosis. H o r i z o n t a l scan.
vitreo-retinal adhesions causes tractional retinal detachments (Fig. 12). Asteroid Hyalosis This senile, degenerative disorder of unknown origin occurs in otherwise healthy eyes, and is uniocular in 75% of cases. Calcium soaps scattered throughout the vitreous form asteroid bodies which remain in suspension, as there is no associated liquefaction. These calcified bodies show multiple, high-amplitude echoes, and demonstrate considerable after-movement on dynamic scanning (Fig. 13). Posterior Vitreous Detachment
Fig. 12 - T r a c t i o n retinal d e t a c h m e n t (arrow). H o r i z o n t a l scan. © 1996 The Royal College of Radiologists, Clinical Radiology, $1, 533-544.
Posterior vitreous detachment (PVD) results from synchysis senilis, a degenerative disorder causing liquefaction and extrusion of fluid from the gel. The gel loses volume, and has increased mobility, remaining suspended from the vitreous base surrounded by retrohyaloid, synchytic fluid. Most cases of synchysis senilis remain uncomplicated and the condition is frequently seen when scanning cataractous eyes. Sometimes, however, vitreous traction causes a retinal tear or avulsion of a peripheral blood vessel, resulting in intragel and retrohyaloid haemorrhage [15]. Dynamic scanning demonstrates a mobile and deformable vitreous, the gel assuming mirror-image configurations, with the eye deviated from side to side (Fig. 14). Failure to move in this way,
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Fig. 14 - (a) Posterior vitreous detachment-eye deviated right. Horizontal scan. (b) PVD-eye deviated left. Horizontal scan.
or asymmetrical suspension, may indicate immobilisation of part of the gel by an adhesion (incomplete PVD), or restriction from a penetrating injury (Fig. 15). Retrohyaloid haemorrhage, in the presence of a posterior vitreoretinal adhesion may incarcerate the gel, resulting in little mobility on dynamic scanning.
colour Doppler studies show no flow within the elevation (Fig. 17). Ocular Tumours
ChoroidaI Metastases These are commoner than primary malignancies and
Optic Nerve Head
Drusen are hyaline, calcific deposits within the substance of the optic nerve head. These collections cast a dense acoustic shadow and sometimes protrude into the vitreous. They may be congenital or acquired, the latter a manifestation of senile macular degeneration (Fig. 16). Diseiform Lesions
These are tumour mimicking lesions caused by raised exudates or haemorrhages in the region of the macula in the end stages of age-related macular degeneration. The early stages are rupture of Bruch's membrane by the penetration of a neovascular membrane derived from the choroid. This tissue may bleed or leak producing subretinal exudate subsequently healing by fibrosis. Although macular degeneration is usually bilateral, the extent, severity and progression is often asymmetrical. A subretinal elevation caused by a disciform lesion may therefore mimic a choroidal turnout. Serial conventional scans may indicate the diagnosis by showing regression of the lesion and
.Fig. 15 Vitreo-retinaladhesion(arrow). Horizontalscan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
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Fig. 16 - Drusen. H o r i z o n t a l scan.
originate most frequently from carcinomas of the breast and bronchus [16,17]. Metastases appear as low, undulating, broad-based lesions due to lateral infiltration along the choroid, and have an affinity with the posterior pole (Fig. 18). A clue to the tumour's primary site is usually given by the history.
Choroidal Melanoma
In the past the diagnosis of ocular melanoma has not always been easy, especially with opaque media. In 1964, Ferry stated that approximately 20% of eyes removed, because they were thought to contain a melanoma, were found to be negative for this condition [18]. Recently the rate of misdiagnosis has fallen to 0.48% [19] due to improved clinical methods including ultrasound. Melanoma is the commonest, primary intraocular turnout in adults, with a highest incidence between the ages of 50 and 60 years. Eighty-five percent of ocular
melanomas arise from the choroid, and 15% from the ciliary body [20]. Occasionally the turnout is asymptomatic and discovered on routine examination, but it can cause decreased visual acuity or a visual field defect. These symptoms are dependent on its size, position and the presence of retinal detachment. If secondary glaucoma develops, the eye becomes acutely painful. Previously enucleation of the eye was advocated, but this~practice has been questioned [21], especially for small turnouts as turnout dissemination during surgery is considered a possible cause of increased death rates in the following two years. A more conservative approach with local resection, photocoagulation or radiotherapy has given ultrasound an important role in management, particularly in eyes with hazy media, as information about size, position, extent and growth of a turnout is readily obtained. The ultrasound appearances of choroidal melanoma are well described [22,23]. Typically, there is a domeshaped mass, deeply embedded in and arising from the choroid. The mass is usually reflective with high acoustic absorbancy appearing as a dense tumour, with some acoustic shadowing. Less frequently, the turnout is low-reflective and there may be a cystic component. An associated exudative retinal detachment may conceal an underlying melanoma from ophthalmoscopic examiiaation (Fig. 19), but scanning reveals the solid nature of the hidden tumour [24]. Some melanomas have a cottage-loaf or mushroom shaped appearance caused by waisting, as they break through Bruch's membrane (the basal lamina of the choroid). This feature is pathognomonic of melanoma (Fig. 20), and is, therefore, important to discover. If the membrane remains intact, the turnout is dome-shaped. M a n y turnouts demonstrate choroidal excavation, which is the presence of relatively lowreflective tumour replacing and enlarging the choroid. Colour Doppler imaging is a simple method of differentiating melanoma from subretinal haemorrhage, showing vascularity of the tumour (Fig. 17) by demonstrating blood flow within it [9]. Care must be taken so that blood flow in the overlying retina is not mistaken for tumour circulation. B scanning is useful in the assessment of scleral erosion and extraocular extension of a melanoma, the extraocular component showing as a low reflective area within the orbital fat (Fig. 21).
Fig. 17 (a) Disciformlesion. Colour Doppler scan. (b) Melanoma.Colour Doppler scan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
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Fig. 18 - Choroidal metastasis (arrows).
Retinoblastoma
This is the commonest, primary intraocular tumour of childhood [25], but is nevertheless rare, occurring in about 1 in 20 000 live births.It normally presents at a late stage with leukocoria (white pupil), but earlier stages are seen in 'at risk' patients being kept under observation. Ninety-four percent of cases are sporadic, but in 6% there is a positive family history, the mode of inheritance being autosomal dominant with incomplete penetrance. Average age of diagnosis is 18 months, and the tumour is bilateral in about one third of cases. The tumour projects from the retina into the vitreous compartment as a white or pinkish mass, and ultrasound frequently shows an extensive lesion. Calcium deposits are clearly shown, and when present are a diagnostic feature (Fig. 22). Invasion of the optic nerve is more readily demonstrated by computed tomography, and it is important to excise a long segment of the nerve when the eye is enucleated. Optic nerve involvement beyond the point of surgical transection is associated with a 65% mortality rate, but if the nerve is uninvolved, the mortality rate is about 8%. However, retinoblast0ma has the best prognosis of all childhood tumours with over 80% survival. Differential diagnosis of leukocoria in a child includes: Coat's disease, which is a severe form of retinal telangiectasia presenting at a later age; toxacariasis, an infestation caused by ingestion of the intestinal roundworm of cats and dogs, the roundworm larvae causing an ocular granuloma; and persistent primary hyperplastic
Fig. 19 (a) M e l a n o m a concealed by retinal detachment. Horizontal scan. (b) Diagram of scan.
vitreous, a developmental disorder typically occurring in a microphthalmic eye. Trauma
Direct examination of the eye is frequently impeded by opaque media following trauma. Early assessment of intraocular damage is required to enable vitrectomy and other microsurgical techniques, to be carried out before chronic internal structural changes develop [26]: Ultrasound is also useful in localization of intraocular foreign bodies composed of reflective material, especially metal or glass (Fig. 23). Blunt trauma causes compression of the anteroposterior diameter of the eye, and corresponding expansion of the equatorial plane. Many cases of trauma occur in young patients with a healthy vitreous, so that progression to retinal detachment is slow, taking several months. Lateral blows which strike the eye immediately anterior to the lateral wall may cause globe rupture. Rupture usually occurs in the equatorial region, and signs include distortion of the normal shape with loss of ocular volume, intravitreal haemorrhage and intraocular air, particularly if there is communication with an ethmoid sinus. © 1996 The Royal College of Radiologists, Clinical Radiology, 51,533 544.
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Fig. 20 - Melanoma bursting through Bruch's membrane (arrows). Choroidal excavation (dark arrow). Vertical scan.
The lens is normally anechoic, and therefore lens subluxation is difficult to evaluate. Complete dislocation is more easily demonstrated, particularly if the lens is cataractous, or if the complete lens lies within an area of vitreous haemorrhage. Bleeding into the vitreous compartment may be confined to the vitreous gel, the subvitreal space, or both. Small haemorrhages are difficult to image, but larger bleeds are easy to detect, and aid delineation of lacunae (lakes of fluid), whose formation indicate impending posterior vitreous detachment (Fig. 24). Dynamic scanning is important to detect vitreoretinal adhesions, which result in traction retinal detachment, and need to be divided during vitrectomy (Fig. 25). If post-traumatic retinal detachment is left untreated, proliferative vitreoretinopathy develops, resulting in the formation of epiretinal and vitreous membranes, and the typical triangle sign on scanning (Fig. 26). Penetrating injuries may cause vitreous impaction at the point of injury, resulting in incomplete PVD and asymmetrical suspension of the gel (Fig. 27).
Colour Doppler Studies A frequency shift in the ultrasound signal returning from sound scatterers (erythrocytes) in blood enables colour Doppler imaging (CDI) to take place. Colour coding of this signal may be done on the basis of direction of flow relative to the ultrasound probe, and traditionally arteries are coded red and veins blue. The ophthalmic artery (1 mm diameter), and even smaller vessels are seen as a flashing colour signal (Fig. 28), superimposed on the conventional real-time B scan [27,28], providing an anatomical display with overlying colour. Normal ocular and orbital vessels may be identified, such as the central retinal artery and central retinal vein (Fig. 29), choroidal and retinal vessels, and the © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
Fig. 21 - (a) Extraocular extension of melanoma (arrow). Horizontal scan. (b) Diagram of scan.
superior ophthalmic vein, and blood flow velocities are calculated from the Doppler spectrograph. Ophthalmic artery flow velocity declines with advancing age, and the normal flow patterns may be used as a baseline for the study of ocular and orbital vascular disease [29]. Flow velocities measured in the central retinal artery (CRA) and central retinal vein (CRV) at the optic nerve head may indicate whether CRA or CRV occlusion has occurred and help predict the development of rubeosis in the latter [30,31]. Although Baxter concluded that no routine application had emerged for CDI in the orbit [32] it is this author's experience that CDI is a useful supportive method of diagnosing intraocular tumours, such as melanomas (Fig. 17), metastases and retinoblastomas, tumour vessels showing vividly as pulsating channels or lakes of colour [9]. Melanoma is occasionally mimicked by benign conditions such as disciform lesions, subretinal
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Fig. 22 - Retinoblastoma showing calcium deposits. Horizontal scan.
haemorrhage, or choroidal folds. In this situation the demonstration of tumour vasculature by CDI is a considerable aid to differential diagnosis. It is also of value in assessment of the effects of radiotherapy, which causes flow velocities and Doppler shifts to decrease, supporting the theory that radiation causes sclerosis of the supply vessels [33]. The ability to demonstrate tumour vasculature may be of relevance when considering new forms of therapy currently under assessment, such as chemotherapy or the linking of cytotoxic drugs
Fig. 24 - L a c u n a i n vitreous haemorrhage (arrow). Horizontal scan.
or radionuclides to monoclonal antibodies against melanoma antigens.
Contrast Agents Not all tumours show vascularity on CDI especially if under 3 m m in size, but in future the intensifying effect of ultrasound contrast agents on the Doppler signal may prove a useful diagnostic aid in the above situations. There is already some evidence that administration of a blood-pool echo-enhancing agent enhances the Doppler signal in ocular tumours [34].
Fig. 23 - Metal splinter (arrow). Vitreous haemorrhage with lacunae. Horizontal scan.
Fig. 25 - Vitreoretinal adhesion with shallow traction retinal detachment (arrow). Vertical scan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
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Fig. 28 - Ophthalmic artery (red). Colour Doppler scan. which provides in vivo microscopic imaging of the iris, ciliary body, anterior chamber and cornea with unparalleled detail. Investigation of glaucoma, iris tumours, scleral conditions and lens implantation is now possible [35].
CONCLUSION
Fig. 26 Proliferativevitreoretinopathyshowing triangle sign.
Anterior Segment Near field artefact obscures clear visualization of the anterior segment in conventional scanning, unless a water-bath is used. Pavlin and colleagues have developed a high frequency (50MHz) ultrasound biomicroscope
Fig. 27 - Lacerated gel with vitreoretinal adhesion (arrow). Vertical scan. t © 1996 The Royal College of Radiologists, Clinical Radiology, Sl, 533 544.
When ophthalmoscopy is precluded by opaque lightconducting media, contact scanning is the simplest, quickest a n d most effective way of imaging the intraocular contents. It is essential before vitreoretinal surgery and early assessment after trauma initiates treatment before chronic changes develop. The image quality of currently available high-resolution general purpose scanners with small-parts probes has made ophthalmic scanning feasible in most radiology departments. Colour Doppler imaging is a pictorially vivid method of diagnosing intraocular tumours, aiding differentiation from mimicking conditions such as disciform lesions, haemorrhage or choroidal folds. It also has applications in central retinal artery and vein occlusion•
Fig. 29 - Central retinal artery (red) and vein (blue). Colour Doppler scan.
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REFERENCES 1 Fielding JA. The eye and orbit. In: Cosgrove D, Meire H, Dewbury K, eds. Clinical Ultrasound. London: Churchill Livingstone 1993; II:62t-658. 2 Lizzi FI, Mortimer AJ. Bioeffects considerations for the safety of diagnostic ultrasound. Journalof UltrasoundMedicine 1988;7(suppl.): 1-38. 3 Restori M, McLeod D. Ultrasound in pre-vitrectomy assessment. Transactions of the OpthalmologicalSociety UK 1977;97:232-234. 4 Richardson J, Wood CM, Mackay LJ et al. A vitreoretinal service. British Medical Journal 1989;299:241-245. 5 Wright JE. Current concepts in orbital diseases (Doyne lecture). Eye
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1988;2:1-11. 6 McLeod D, Restori M. Rapid B-scanning in ophthalmology. In: Barnett E, Morley P, eds. Clinical diagnostic ultrasound. Oxford: Blackwell Scientific Publications 1985; 111-120. 7 Fielding JA. Dynamic scanning in the assessment of intraocular abnormalities. Procedings of the 48th Annual Congress. British Journal of Radiology 1990;63:53. 8 Lieb WE, Cohen SM, Merton DA et aL Colour Doppler imaging of the eye and orbit. Archives of Ophthalmology 1991;109:527531. 9 Fielding JA. Imaging the eye with ultrasound. MD Thesis: The University of Liverpool, 1993. 10 Morse PH, Lattice degeneration of the retina and retinal detachment, American Journal of Opthalmology 1974;78:930-934. 11 Jaffe NA. Complications of acute posterior vitreous detachment. Archives of Ophthalmology 1968;79:568-571. 12 Foulds WS. Aetiotogy of retinal detachment. Transactions of the Ophthalmological Society UK 1975;95:118-128. 13 Schepens CL, MArden S. Data on the natural history of retinal detachment, American Journal of Ophthalmology 1966;61:213226. 14 Forrester JV, Lee WR, Williamson J. The pathology of vitreous haemorrhage. Archives of Ohthalmology 1978;95:703-710. 15 Mewis L, Young SE. Breast carcinoma metastatic to the choroid analysis of 67 patients. Ophthalmology 1982;89:147-151. 16 Kanski JJ. Complications of acute posterior vitreous detachment. American Journal of Ophthalrnology 1975;80:44-46. 17 Stephens RF, Shields JA. Diagnosis and management of cancer metastatic to the uvea: a study of 70 cases. Ophthalmology 1979; 86:1336-1349. 18 Ferry AP. Lesions mistaken for malignant melanomas of the posterior uvea. Archives of Ophthalmology 1964;72:463-469. 19 Collaborative Ocular Melanoma Study Group. Accuracy of
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27 28 29 30 31 32 33 34 35
diagnosis of choroidal melanomas in the collaborative study group. Archives of Ophthalmology 1990; 108:1268-1273. Jakobiec FA, Levinson AW. Choroidal melanoma: aetiology and diagnosis. Clinical Modulesfor Ophthalmologists. 1985;3:module 5. Foulds WS. Current options in the management of choroidal melanoma. Transactions of the Ophthalmological Society UK 1983; 103:28-34. Baum G. Ultrasound characteristics of malignant melanoma. Archives of Ophthalmology 1967;78:12-15. Fuller DG, Synder WB, Hutton WL et al. Ultrasonographic features of choroidal malignant melanomas. Archives of Opthalmology 1979;97:1465-1472. Jack RL, Coleman DJ. Detection of retinal detachments secondary to choroidal melanoma with B-scan ultrasound. American Journal of Ophthalmology 1972;74:1057-1064. Char DH. Current concepts in retinoblastoma. Annals of Ophthalmology 1980;12:792-804. Passani F, Barco L, Venturi G. Pre-vitrectomy examination of the traumatised eye. In: Hillman JS, Le May MM, eds. Ophthalmic ultrasonography. The Hague: Martinus Nijhoff/W Junk 1983;121125. Taylor KJW, Holland S. Doppler Ultrasound, 1: Basic principles, instrumentation, and pitfalls. Radiology 1990;174:297-307. Scoutt LM, Zawin ML, Taylor KJW. Doppler Ultrasound, 11: Clinical applications. Radiology 1990;174:309-319. GuthoffRF, Berger RW, Winkler P e t al. Doppler ultrasonography of the ophthalmic and central retinal vessels. Archives of Ophthalmology 1991;109:532-536. Williamson TH, Baxter GM, Dutton GN. Colour Doppler velocimetry of the optic nerve head in arterial occlusion. Ophthalmology 1993;100:312-317. Baxter GM, Williamson TH. Colour Doppler flow imaging in central retinal vein occlusion: a new diagnostic technique? Radiology 1993;187.3:847-850. Baxter GM, Williamson TH. Colour flow imaging of the orbit concept or diagnostic tool? Clinical Radiology 1994;49:845=846. GuthoffRF, Berger RW, Winkler P e t al. Doppler ultrasonography of malignant melanomas of the uvea. Archives of Ophthalmology 1991;109:537-541. Cennamo G , Rosa N, Vallone G F et al. First experience with a new echographic contrast agent. British Journal of Ophthalmology 1994;78:823-826. Pavlin CJ, Easterbrook M, Harasiewicz K et al. An ultrasound biomicroscopic analysis of angle-closure glaucoma secondary to ciliochoroidal effusion in IgA nephropathy. American Journal of Ophthalmology 1993;116:341-345.
© 1996The Royal College of Radiologists, ClinicalRadiology, 51,533-544.
Pictorial Review Ocular Ultrasound J. A. FIELDING
Department of Radiology, Royal Shrewsbury Hospital, Shropshire, UK
The anatomy of the eye is faithfully reproduced by high frequency ultrasound. When the light-conducting media are opacified by cataract, haemorrhage or membranes preventing clinical examination by ophthalmoscopy, ultrasonography is the most practicable and rapid method of obtaining images of the posterior segment. Contact scanning is a simple technique which requires careful application, releasing information for diagnosis and pre-operative planning, and providing an accurate depiction of the internal structure. The 2-D images assessed in real-time enable the operator to construct mentally a 3-D concept of intraocular pathological processes. Ophthalmic ultrasonography has long been the province of ophthalmologists, often using dedicated equipment. However with the advent of high resolution general purpose scanners with small parts probes, radiologists are becoming increasingly involved in this field [!]. The globe is the dominant structure in the anterior orbit, and its cystic structure and superficial position make it ideal for ultrasound examination (Fig. 1). To understand the pathological appearances of the detached retina,~choroid and vitreous, a clear knowledge of the anatomy and fixed anchoring points of the inner and middle coats and vitreous is required (Fig. 2). Ultras(ound is the quickest and simplest method of imagin'g the eye, and at energy levels used for diagnostic purposes, no known adverse effects have been demonstrated [2]. Opaque media caused by cataract, haemorrhage or vitreous membranes conceal the intraocular contents from clinical examination, making ultrasonography the most useful examination for assessment and prior to vitrectomy [3,4]. Although computed tomography [5] and magnetic resonance imaging are invaluable in many orbital conditions, they cannot scan in real-time, lack spatial resolution, and have considerable limitations when imaging the vitreous and retina, where ultrasound contributes more to tissue diagnosis. Dynamic scanning is important, and with increasing experience the examiner is able to study characteristics of the motion and topography of pathological intraocular conditions [6], enabling differentiation of retinal detachment and vitreous membrane, or tumour and haemorrhage [7]. Colour Doppler imaging is a recent development, facilitating the study of ocular and orbital blood flow. Colour coded Doppler information is superimposed upon a conventional B scan image, so that structure and blood flow are seen simultaneously, aiding identification of small orbital vessels, direction of flow, and calculation of flow velocity in vascular disease and tumours [8]. Correspondence to: Dr J.A. Fielding, Department of Radiology, Royal Shrewsbury Hospital, Shropshire SY3 8XG, UK. © 1996 The Royal Collegeof Radiologists.
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The image resolution of current ultrasound scanners has brought eye scanning within the scope of departments possessing a short-focus 7.5 or 10 MHz real-time, small parts probe [9]. A built-in stand-off facility improves image quality of the anterior structures, but is not necessary for the posterior segment. Sector scanning is carried out with the patient lying supine, when the pull of gravity is exerted in the direction of the optic axis. This enables a detached vitreous still suspended from the vitreous base, or the sedimentation of blood, to be assessed with the patient in a relaxed and supported state. However, some operators prefer the patient to be scanned in the sitting position. The simplest way of examining the eye is contact scanning, when the probe is placed directly on the closed eyelid, with an intervening sterile coupling gel. The aim is to image the globe while static, and during rapid eye movement with the patient deviating the eyes to the right and left side. Mobility of the pathological vitreous and retina is observed during dynamic scanning, together with vitreoretinal adhesions, and following an ocular excursion, after-movements may continue for approximately a second [6]. The gel moves as a complete body, but the detached retina undulates as a membrane, unless fixed by fibrosis. Choroidal tumours are solid, and their attachment to the ocular wall is apparent, whereas vitreous, retrohyaloid or sub-retinal haemorrhage may swirl and sediment during eye movements. When vitreoretinal microsurgical techniques are being considered, information provided by these methods of scanning about the structure and mobility of the ocular contents is of great importance when assessing surgical approach and prognosis.
Indications The indications for eye scanning are as follows: (a) opaque light-conducting media, precluding ophthalmoscopy; (b) suspected intra-ocular tumour solid lesions are readily identified, positioned and measured by ultrasound; (c) differentiation of serious and solid retinal detachment. Detachments may conceal a tumour - the subretinal area is clearly demonstrated by ultrasound; (d) examination of the vitreous; (e) localization of foreign bodies; (f) ocular measurements (biometry - needs calibrated equipment); (g) proptosis; (h) colour Doppler imaging in ocular and orbital vascular disease and tumours. Patients with opaque, light-conducting media are the majority of referrals, especially those with cataracts and
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Fig. 1 - Normal eye showing iris (small arrow), and posterior lens surface (arrow). Horizontal scan.
haemorrhages. It is not necessary to scan every patient with a cataract, but if there are concurrent symptoms, for example, inflammation, pain, rapidly worsening vision, or the development of glaucoma, then a scan must be performed to determine any co-existent pathology. Prior to vitreoretinal surgery ultrasound assessment of the globe is mandatory [4]. Information required includes: (a) the state of the vitreous; (b) the position and extent of any intraocular lesion; (c) the condition of the retina, and particularly, the macula; (d) the mobility of the contents of the globe, which influences operability; (e) the relation between the vitreous and retina, mapping vitreoretinal adhesions.
Fig. 3 - Subcapsular cataract. Horizontal scan.
PATHOLOGY A range of the most commonly encountered and important clinical entities is described and illustrated. Lens
The lens contents are normally ar~echoic but immature cataract forms lenticular opacities seen as reflective areas. Subcapsular cataract leaves a deposition of reflective material outlining the lens capsule. A mature cataract causes a totally reflective cortex resulting in a very dense lens on scanning (Fig. 3). A plastic lens implant is frequently inserted after cataract extraction. It is important to be aware of the presence of these as they cause a dense artefact in the vitreous, so scanning must be carried out in a plane which avoids the implant (Fig. 4). Retina and Choroid Retinal Detachment
Fig. 2
Section of eye.
There are two main types of retinal detachment: rhegmatogenous (arising from a retinal break or tear), and non-rhegmatogenous (or secondary detachment): Retinal breaks which result in detachment are caused by weakness in the peripheral retina from degeneration (Fig. 5), for example lattice degeneration in myopes [10] and vitreoretinal traction from a detached vitreous [11]. The forms of non-rhegmatogenous retinal detachment are tractional and exudative [12,13]. Tractional © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533-544.
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Fig. 4 - I m p l a n t artefact (arrow). Horizontal scan. Fig. 6 Classic V-shaped retinal detachment and collapsed vitreous (arrow). Horizontal scan.
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detachment occurs when contracting vitreoretinal membranes pull the sensory retina away from the pigment epithelium, resulting in angular lesions. Diabetes and penetrating trauma are the main causes. Exudative detachment occurs when subretinal fluid from the choroid enters the subretinal space in inflammation (uveal effusion syndrome) or t u m o u r . Firm attachments of the retina exist at the ora serrata and the optic nerve head, ensuring that detachment does not extend beyond these sites (Fig. 6). A classical, total detachment, therefore, shows a funnel-shaped appearance, and in a recent detachment, dynamic scanning reveals an undulating, sinuous or whiplash motion of the retinal leaves. A minority of retinal detachments remain stationary for some years, but if untreated most detachments become total and progressively immobile, because of the development of epiretinal fibrosis. The retina contracts to form a taut membrane, stretched between the optic disc and ora serrata (Fig. 2b). Choroidal Detachment
Fig, 5 - Retinal tear (small arrow) and detachment (arrow). Horizontal scan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
Choroidal detachment is caused by fluid in the suprachoroidal space, limited by the choroidal anchoring points - anteriorly at the scleral spur, posteriorly near the exit foramina of the vortex veins. A complete detachment, therefore, appears on scanning as convex indentations of the globe. If the vortex veins are absent or avulsed, the detachment may extend to the optic disc. Choroidal detachment may occur with retinal detachment in exudative conditions, but also with rhegmatogenous detachment [6]. Ultrasound may reveal choroidal tumour (melanoma, secondary deposit or retinoblastoma) as the cause of an exudative detachment; but the aetiology also includes endogenous uveitis (Fig. 7) and infection. Subchoroidal haemorrhage is a serious
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r
Fig. 7
Choroiditis. Colour Doppler scan.
post-surgical complication but it also occasionally occurs spontaneously (Fig. 8). Vitreous
The vitreous gel is transonic, but with careful adjustment of the scanner's sensitivity, dynamic scanning shows some undulations of the posterior hyaloid surface, with eye movements. The vitreous is imaged more easily if occupied, or surrounded by blood or other pathological material (Figs 9 & 10), and its motion is that of an elastic body.
Fig. 9 - Vitreous haemorrhage. Horizontal scan.
Vitreous Haemorrhage Small haemorrhages may be difficult to demonstrate and usually resolve after an interval. Larger bleeds are seen more easily as low density echoes, which may persist with development of fibrinous membranes (Fig. 11). Fibrosis or organization is an unusual sequel to vitreous haemorrhage, and is usually associated with trauma or diabetes and vasculitis [14], resulting in the formation of epiretinal membranes (proliferative vitreoretinopathy). Contracture of these membranes with
Fig. 8 - Subchoroidal haemorrhage. Colour Doppler scan.
Fig. 10 - Subvitreal haemorrhage. Vertical scan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544
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Fig. 11 - F i b r i n o n s m e m b r a n e s w i t h i n vitreous. H o r i z o n t a l scan.
Fig. 13 - A s t e r o i d hyalosis. H o r i z o n t a l scan.
vitreo-retinal adhesions causes tractional retinal detachments (Fig. 12). Asteroid Hyalosis This senile, degenerative disorder of unknown origin occurs in otherwise healthy eyes, and is uniocular in 75% of cases. Calcium soaps scattered throughout the vitreous form asteroid bodies which remain in suspension, as there is no associated liquefaction. These calcified bodies show multiple, high-amplitude echoes, and demonstrate considerable after-movement on dynamic scanning (Fig. 13). Posterior Vitreous Detachment
Fig. 12 - T r a c t i o n retinal d e t a c h m e n t (arrow). H o r i z o n t a l scan. © 1996 The Royal College of Radiologists, Clinical Radiology, $1, 533-544.
Posterior vitreous detachment (PVD) results from synchysis senilis, a degenerative disorder causing liquefaction and extrusion of fluid from the gel. The gel loses volume, and has increased mobility, remaining suspended from the vitreous base surrounded by retrohyaloid, synchytic fluid. Most cases of synchysis senilis remain uncomplicated and the condition is frequently seen when scanning cataractous eyes. Sometimes, however, vitreous traction causes a retinal tear or avulsion of a peripheral blood vessel, resulting in intragel and retrohyaloid haemorrhage [15]. Dynamic scanning demonstrates a mobile and deformable vitreous, the gel assuming mirror-image configurations, with the eye deviated from side to side (Fig. 14). Failure to move in this way,
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Fig. 14 - (a) Posterior vitreous detachment-eye deviated right. Horizontal scan. (b) PVD-eye deviated left. Horizontal scan.
or asymmetrical suspension, may indicate immobilisation of part of the gel by an adhesion (incomplete PVD), or restriction from a penetrating injury (Fig. 15). Retrohyaloid haemorrhage, in the presence of a posterior vitreoretinal adhesion may incarcerate the gel, resulting in little mobility on dynamic scanning.
colour Doppler studies show no flow within the elevation (Fig. 17). Ocular Tumours
ChoroidaI Metastases These are commoner than primary malignancies and
Optic Nerve Head
Drusen are hyaline, calcific deposits within the substance of the optic nerve head. These collections cast a dense acoustic shadow and sometimes protrude into the vitreous. They may be congenital or acquired, the latter a manifestation of senile macular degeneration (Fig. 16). Diseiform Lesions
These are tumour mimicking lesions caused by raised exudates or haemorrhages in the region of the macula in the end stages of age-related macular degeneration. The early stages are rupture of Bruch's membrane by the penetration of a neovascular membrane derived from the choroid. This tissue may bleed or leak producing subretinal exudate subsequently healing by fibrosis. Although macular degeneration is usually bilateral, the extent, severity and progression is often asymmetrical. A subretinal elevation caused by a disciform lesion may therefore mimic a choroidal turnout. Serial conventional scans may indicate the diagnosis by showing regression of the lesion and
.Fig. 15 Vitreo-retinaladhesion(arrow). Horizontalscan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
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Fig. 16 - Drusen. H o r i z o n t a l scan.
originate most frequently from carcinomas of the breast and bronchus [16,17]. Metastases appear as low, undulating, broad-based lesions due to lateral infiltration along the choroid, and have an affinity with the posterior pole (Fig. 18). A clue to the tumour's primary site is usually given by the history.
Choroidal Melanoma
In the past the diagnosis of ocular melanoma has not always been easy, especially with opaque media. In 1964, Ferry stated that approximately 20% of eyes removed, because they were thought to contain a melanoma, were found to be negative for this condition [18]. Recently the rate of misdiagnosis has fallen to 0.48% [19] due to improved clinical methods including ultrasound. Melanoma is the commonest, primary intraocular turnout in adults, with a highest incidence between the ages of 50 and 60 years. Eighty-five percent of ocular
melanomas arise from the choroid, and 15% from the ciliary body [20]. Occasionally the turnout is asymptomatic and discovered on routine examination, but it can cause decreased visual acuity or a visual field defect. These symptoms are dependent on its size, position and the presence of retinal detachment. If secondary glaucoma develops, the eye becomes acutely painful. Previously enucleation of the eye was advocated, but this~practice has been questioned [21], especially for small turnouts as turnout dissemination during surgery is considered a possible cause of increased death rates in the following two years. A more conservative approach with local resection, photocoagulation or radiotherapy has given ultrasound an important role in management, particularly in eyes with hazy media, as information about size, position, extent and growth of a turnout is readily obtained. The ultrasound appearances of choroidal melanoma are well described [22,23]. Typically, there is a domeshaped mass, deeply embedded in and arising from the choroid. The mass is usually reflective with high acoustic absorbancy appearing as a dense tumour, with some acoustic shadowing. Less frequently, the turnout is low-reflective and there may be a cystic component. An associated exudative retinal detachment may conceal an underlying melanoma from ophthalmoscopic examiiaation (Fig. 19), but scanning reveals the solid nature of the hidden tumour [24]. Some melanomas have a cottage-loaf or mushroom shaped appearance caused by waisting, as they break through Bruch's membrane (the basal lamina of the choroid). This feature is pathognomonic of melanoma (Fig. 20), and is, therefore, important to discover. If the membrane remains intact, the turnout is dome-shaped. M a n y turnouts demonstrate choroidal excavation, which is the presence of relatively lowreflective tumour replacing and enlarging the choroid. Colour Doppler imaging is a simple method of differentiating melanoma from subretinal haemorrhage, showing vascularity of the tumour (Fig. 17) by demonstrating blood flow within it [9]. Care must be taken so that blood flow in the overlying retina is not mistaken for tumour circulation. B scanning is useful in the assessment of scleral erosion and extraocular extension of a melanoma, the extraocular component showing as a low reflective area within the orbital fat (Fig. 21).
Fig. 17 (a) Disciformlesion. Colour Doppler scan. (b) Melanoma.Colour Doppler scan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
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Fig. 18 - Choroidal metastasis (arrows).
Retinoblastoma
This is the commonest, primary intraocular tumour of childhood [25], but is nevertheless rare, occurring in about 1 in 20 000 live births.It normally presents at a late stage with leukocoria (white pupil), but earlier stages are seen in 'at risk' patients being kept under observation. Ninety-four percent of cases are sporadic, but in 6% there is a positive family history, the mode of inheritance being autosomal dominant with incomplete penetrance. Average age of diagnosis is 18 months, and the tumour is bilateral in about one third of cases. The tumour projects from the retina into the vitreous compartment as a white or pinkish mass, and ultrasound frequently shows an extensive lesion. Calcium deposits are clearly shown, and when present are a diagnostic feature (Fig. 22). Invasion of the optic nerve is more readily demonstrated by computed tomography, and it is important to excise a long segment of the nerve when the eye is enucleated. Optic nerve involvement beyond the point of surgical transection is associated with a 65% mortality rate, but if the nerve is uninvolved, the mortality rate is about 8%. However, retinoblast0ma has the best prognosis of all childhood tumours with over 80% survival. Differential diagnosis of leukocoria in a child includes: Coat's disease, which is a severe form of retinal telangiectasia presenting at a later age; toxacariasis, an infestation caused by ingestion of the intestinal roundworm of cats and dogs, the roundworm larvae causing an ocular granuloma; and persistent primary hyperplastic
Fig. 19 (a) M e l a n o m a concealed by retinal detachment. Horizontal scan. (b) Diagram of scan.
vitreous, a developmental disorder typically occurring in a microphthalmic eye. Trauma
Direct examination of the eye is frequently impeded by opaque media following trauma. Early assessment of intraocular damage is required to enable vitrectomy and other microsurgical techniques, to be carried out before chronic internal structural changes develop [26]: Ultrasound is also useful in localization of intraocular foreign bodies composed of reflective material, especially metal or glass (Fig. 23). Blunt trauma causes compression of the anteroposterior diameter of the eye, and corresponding expansion of the equatorial plane. Many cases of trauma occur in young patients with a healthy vitreous, so that progression to retinal detachment is slow, taking several months. Lateral blows which strike the eye immediately anterior to the lateral wall may cause globe rupture. Rupture usually occurs in the equatorial region, and signs include distortion of the normal shape with loss of ocular volume, intravitreal haemorrhage and intraocular air, particularly if there is communication with an ethmoid sinus. © 1996 The Royal College of Radiologists, Clinical Radiology, 51,533 544.
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Fig. 20 - Melanoma bursting through Bruch's membrane (arrows). Choroidal excavation (dark arrow). Vertical scan.
The lens is normally anechoic, and therefore lens subluxation is difficult to evaluate. Complete dislocation is more easily demonstrated, particularly if the lens is cataractous, or if the complete lens lies within an area of vitreous haemorrhage. Bleeding into the vitreous compartment may be confined to the vitreous gel, the subvitreal space, or both. Small haemorrhages are difficult to image, but larger bleeds are easy to detect, and aid delineation of lacunae (lakes of fluid), whose formation indicate impending posterior vitreous detachment (Fig. 24). Dynamic scanning is important to detect vitreoretinal adhesions, which result in traction retinal detachment, and need to be divided during vitrectomy (Fig. 25). If post-traumatic retinal detachment is left untreated, proliferative vitreoretinopathy develops, resulting in the formation of epiretinal and vitreous membranes, and the typical triangle sign on scanning (Fig. 26). Penetrating injuries may cause vitreous impaction at the point of injury, resulting in incomplete PVD and asymmetrical suspension of the gel (Fig. 27).
Colour Doppler Studies A frequency shift in the ultrasound signal returning from sound scatterers (erythrocytes) in blood enables colour Doppler imaging (CDI) to take place. Colour coding of this signal may be done on the basis of direction of flow relative to the ultrasound probe, and traditionally arteries are coded red and veins blue. The ophthalmic artery (1 mm diameter), and even smaller vessels are seen as a flashing colour signal (Fig. 28), superimposed on the conventional real-time B scan [27,28], providing an anatomical display with overlying colour. Normal ocular and orbital vessels may be identified, such as the central retinal artery and central retinal vein (Fig. 29), choroidal and retinal vessels, and the © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
Fig. 21 - (a) Extraocular extension of melanoma (arrow). Horizontal scan. (b) Diagram of scan.
superior ophthalmic vein, and blood flow velocities are calculated from the Doppler spectrograph. Ophthalmic artery flow velocity declines with advancing age, and the normal flow patterns may be used as a baseline for the study of ocular and orbital vascular disease [29]. Flow velocities measured in the central retinal artery (CRA) and central retinal vein (CRV) at the optic nerve head may indicate whether CRA or CRV occlusion has occurred and help predict the development of rubeosis in the latter [30,31]. Although Baxter concluded that no routine application had emerged for CDI in the orbit [32] it is this author's experience that CDI is a useful supportive method of diagnosing intraocular tumours, such as melanomas (Fig. 17), metastases and retinoblastomas, tumour vessels showing vividly as pulsating channels or lakes of colour [9]. Melanoma is occasionally mimicked by benign conditions such as disciform lesions, subretinal
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Fig. 22 - Retinoblastoma showing calcium deposits. Horizontal scan.
haemorrhage, or choroidal folds. In this situation the demonstration of tumour vasculature by CDI is a considerable aid to differential diagnosis. It is also of value in assessment of the effects of radiotherapy, which causes flow velocities and Doppler shifts to decrease, supporting the theory that radiation causes sclerosis of the supply vessels [33]. The ability to demonstrate tumour vasculature may be of relevance when considering new forms of therapy currently under assessment, such as chemotherapy or the linking of cytotoxic drugs
Fig. 24 - L a c u n a i n vitreous haemorrhage (arrow). Horizontal scan.
or radionuclides to monoclonal antibodies against melanoma antigens.
Contrast Agents Not all tumours show vascularity on CDI especially if under 3 m m in size, but in future the intensifying effect of ultrasound contrast agents on the Doppler signal may prove a useful diagnostic aid in the above situations. There is already some evidence that administration of a blood-pool echo-enhancing agent enhances the Doppler signal in ocular tumours [34].
Fig. 23 - Metal splinter (arrow). Vitreous haemorrhage with lacunae. Horizontal scan.
Fig. 25 - Vitreoretinal adhesion with shallow traction retinal detachment (arrow). Vertical scan. © 1996 The Royal College of Radiologists, Clinical Radiology, 51, 533 544.
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Fig. 28 - Ophthalmic artery (red). Colour Doppler scan. which provides in vivo microscopic imaging of the iris, ciliary body, anterior chamber and cornea with unparalleled detail. Investigation of glaucoma, iris tumours, scleral conditions and lens implantation is now possible [35].
CONCLUSION
Fig. 26 Proliferativevitreoretinopathyshowing triangle sign.
Anterior Segment Near field artefact obscures clear visualization of the anterior segment in conventional scanning, unless a water-bath is used. Pavlin and colleagues have developed a high frequency (50MHz) ultrasound biomicroscope
Fig. 27 - Lacerated gel with vitreoretinal adhesion (arrow). Vertical scan. t © 1996 The Royal College of Radiologists, Clinical Radiology, Sl, 533 544.
When ophthalmoscopy is precluded by opaque lightconducting media, contact scanning is the simplest, quickest a n d most effective way of imaging the intraocular contents. It is essential before vitreoretinal surgery and early assessment after trauma initiates treatment before chronic changes develop. The image quality of currently available high-resolution general purpose scanners with small-parts probes has made ophthalmic scanning feasible in most radiology departments. Colour Doppler imaging is a pictorially vivid method of diagnosing intraocular tumours, aiding differentiation from mimicking conditions such as disciform lesions, haemorrhage or choroidal folds. It also has applications in central retinal artery and vein occlusion•
Fig. 29 - Central retinal artery (red) and vein (blue). Colour Doppler scan.
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REFERENCES 1 Fielding JA. The eye and orbit. In: Cosgrove D, Meire H, Dewbury K, eds. Clinical Ultrasound. London: Churchill Livingstone 1993; II:62t-658. 2 Lizzi FI, Mortimer AJ. Bioeffects considerations for the safety of diagnostic ultrasound. Journalof UltrasoundMedicine 1988;7(suppl.): 1-38. 3 Restori M, McLeod D. Ultrasound in pre-vitrectomy assessment. Transactions of the OpthalmologicalSociety UK 1977;97:232-234. 4 Richardson J, Wood CM, Mackay LJ et al. A vitreoretinal service. British Medical Journal 1989;299:241-245. 5 Wright JE. Current concepts in orbital diseases (Doyne lecture). Eye
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1988;2:1-11. 6 McLeod D, Restori M. Rapid B-scanning in ophthalmology. In: Barnett E, Morley P, eds. Clinical diagnostic ultrasound. Oxford: Blackwell Scientific Publications 1985; 111-120. 7 Fielding JA. Dynamic scanning in the assessment of intraocular abnormalities. Procedings of the 48th Annual Congress. British Journal of Radiology 1990;63:53. 8 Lieb WE, Cohen SM, Merton DA et aL Colour Doppler imaging of the eye and orbit. Archives of Ophthalmology 1991;109:527531. 9 Fielding JA. Imaging the eye with ultrasound. MD Thesis: The University of Liverpool, 1993. 10 Morse PH, Lattice degeneration of the retina and retinal detachment, American Journal of Opthalmology 1974;78:930-934. 11 Jaffe NA. Complications of acute posterior vitreous detachment. Archives of Ophthalmology 1968;79:568-571. 12 Foulds WS. Aetiotogy of retinal detachment. Transactions of the Ophthalmological Society UK 1975;95:118-128. 13 Schepens CL, MArden S. Data on the natural history of retinal detachment, American Journal of Ophthalmology 1966;61:213226. 14 Forrester JV, Lee WR, Williamson J. The pathology of vitreous haemorrhage. Archives of Ohthalmology 1978;95:703-710. 15 Mewis L, Young SE. Breast carcinoma metastatic to the choroid analysis of 67 patients. Ophthalmology 1982;89:147-151. 16 Kanski JJ. Complications of acute posterior vitreous detachment. American Journal of Ophthalrnology 1975;80:44-46. 17 Stephens RF, Shields JA. Diagnosis and management of cancer metastatic to the uvea: a study of 70 cases. Ophthalmology 1979; 86:1336-1349. 18 Ferry AP. Lesions mistaken for malignant melanomas of the posterior uvea. Archives of Ophthalmology 1964;72:463-469. 19 Collaborative Ocular Melanoma Study Group. Accuracy of
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diagnosis of choroidal melanomas in the collaborative study group. Archives of Ophthalmology 1990; 108:1268-1273. Jakobiec FA, Levinson AW. Choroidal melanoma: aetiology and diagnosis. Clinical Modulesfor Ophthalmologists. 1985;3:module 5. Foulds WS. Current options in the management of choroidal melanoma. Transactions of the Ophthalmological Society UK 1983; 103:28-34. Baum G. Ultrasound characteristics of malignant melanoma. Archives of Ophthalmology 1967;78:12-15. Fuller DG, Synder WB, Hutton WL et al. Ultrasonographic features of choroidal malignant melanomas. Archives of Opthalmology 1979;97:1465-1472. Jack RL, Coleman DJ. Detection of retinal detachments secondary to choroidal melanoma with B-scan ultrasound. American Journal of Ophthalmology 1972;74:1057-1064. Char DH. Current concepts in retinoblastoma. Annals of Ophthalmology 1980;12:792-804. Passani F, Barco L, Venturi G. Pre-vitrectomy examination of the traumatised eye. In: Hillman JS, Le May MM, eds. Ophthalmic ultrasonography. The Hague: Martinus Nijhoff/W Junk 1983;121125. Taylor KJW, Holland S. Doppler Ultrasound, 1: Basic principles, instrumentation, and pitfalls. Radiology 1990;174:297-307. Scoutt LM, Zawin ML, Taylor KJW. Doppler Ultrasound, 11: Clinical applications. Radiology 1990;174:309-319. GuthoffRF, Berger RW, Winkler P e t al. Doppler ultrasonography of the ophthalmic and central retinal vessels. Archives of Ophthalmology 1991;109:532-536. Williamson TH, Baxter GM, Dutton GN. Colour Doppler velocimetry of the optic nerve head in arterial occlusion. Ophthalmology 1993;100:312-317. Baxter GM, Williamson TH. Colour Doppler flow imaging in central retinal vein occlusion: a new diagnostic technique? Radiology 1993;187.3:847-850. Baxter GM, Williamson TH. Colour flow imaging of the orbit concept or diagnostic tool? Clinical Radiology 1994;49:845=846. GuthoffRF, Berger RW, Winkler P e t al. Doppler ultrasonography of malignant melanomas of the uvea. Archives of Ophthalmology 1991;109:537-541. Cennamo G , Rosa N, Vallone G F et al. First experience with a new echographic contrast agent. British Journal of Ophthalmology 1994;78:823-826. Pavlin CJ, Easterbrook M, Harasiewicz K et al. An ultrasound biomicroscopic analysis of angle-closure glaucoma secondary to ciliochoroidal effusion in IgA nephropathy. American Journal of Ophthalmology 1993;116:341-345.
© 1996The Royal College of Radiologists, ClinicalRadiology, 51,533-544.