REVIEW

The assessment of ocular injury by ultrasound

J.A. Fielding*

Radiology Department, Royal Shrewsbury Hospital NHS Trust, Shrewsbury, UK

Received 10 July 2003; received in revised form 3 October 2003; accepted 9 October 2003

KEYWORDSEye; Injuries; Ultrasound

Ocular trauma is readily investigated by ultrasound, which is of particular value whenthe light conducting media are opacified by haemorrhage or other injury. In thissituation, direct visualization of the ocular contents by ophthalmoscopy is difficult orimpossible. Severe complications are treated by microsurgical techniques, andultrasound evaluation represents the only practicable method of examination forsurgical planning. This review illustrates the grey-scale (B scan or two-dimensional)features of the traumatized eye and describes the examination technique.q 2004 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Introduction

Examination of the intra-ocular contents byophthalmoscopy is dependent upon transparentlight-conducting media: the cornea, the aqueoushumour, the lens and vitreous gel. After trauma,the media are frequently opacified by haemor-rhage, laceration, scarring or cataract. Internalinjury is often more serious than is immediatelyapparent, and contusional damage to posteriorsegment structures carries an unfavourable visualprognosis.1 The aim of surgery is to intervene at anearly stage, so that vitrectomy and other micro-surgical techniques are carried out before chronic,irreversible, changes develop which threaten thepatient’s sight.2 The results of vitreous surgery inposterior segment trauma support the concept ofearly secondary intra-ocular reconstruction, sur-gery undertaken before development of retinaldetachment, which improves the prognosis forvisual recovery.3 Vitrectomy, with severance ofadhesions, is carried out by inserting microsurgicalinstruments through the pars plana. A suction-cutter shears off pieces of the vitreous, which areaspirated by the pump, while positive pressureis maintained by infusion. The indications for

vitrectomy are dense and persistent vitreoushaemorrhage, the formation of vitreous mem-branes, vitreo-retinal adhesions and tractionalretinal detachment, particularly if progressing toinvolve the macula.4 –6

Before surgery, it is helpful to have knowledge ofthe degree of internal derangement, and in thepresence of opaque media, ultrasound has provedthe ideal tool. Information is provided aboutvitreous haemorrhage, lens dislocation and rup-ture, detachment of the coats, globe rupture andforeign bodies. Ophthalmic ultrasonography hasoften been the province of ophthalmologists usingdedicated equipment. However, due to the excel-lent quality of high-resolution images produced bycurrently available general purpose scanners withsmall parts probes, ocular ultrasound is within thescope of the interested radiologist. At energy levelsused for diagnostic purposes, no known adverseeffects have been demonstrated.7 Although manysurgeons consider it advantageous to perform theultrasound examination as an adjunct to clinicalexamination, thus having first-hand insight intointra-ocular structures and dynamics before oper-ation, others rely on a radiologist or other trainedoperator.

The eye is the prominent organ in the anteriororbit, its cystic structure and superficial positionmaking it ideal for ultrasound examination (Fig. 1).Although computed tomography (CT) and magneticresonance imaging (MRI) are invaluable in manyorbital conditions, they lack the immediacy and

0009-9260/$ - see front matter q 2004 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.doi:10.1016/j.crad.2003.10.010

Clinical Radiology (2004) 59, 301–312

*Guarantor and correspondent: J.A. Fielding, RadiologyDepartment, Royal Shrewsbury Hospital NHS Trust, Mytton OakRoad, Shrewsbury SY3 8XQ, UK. Tel: þ44-1743-261000, x3279;fax: þ44-1743-261439.

E-mail address: jafielding@doctors.org.uk

simplicity of ultrasound, cannot produce real-timeimages, and have considerable limitations whenimaging the vitreous and retina, whereas ultra-sound contributes more to tissue diagnosis.

Dynamic examination is important, and withincreasing experience the examiner is able tostudy characteristics of the motion and topographyof pathological intra-ocular conditions,8 enablingidentification of detachment of the coats, vitreousmembranes and vitreo-retinal adhesions.

To interpret images of the pathological eye it isvital to have a clear understanding of the anatomyand points of firm attachment of the vitreous,retina and choroid (Fig. 2).

Patients and methods

The images included in this review are from

patients with opaque media after ocular trauma,referred by ophthalmologists in the county ofShropshire. All examinations were carried out bythe author over the last decade. Through-the-lidcontact imaging was employed with a standard,water-soluble coupling gel, using a very gentletechnique to cause minimal discomfort to theinjured eye. Children tolerate the examinationwell. With open wounds, a sterile sheath is placedover the probe, or a 3 mm sterile gel pad is used tocover the eyelid. The images demonstrated arefrom high-resolution ultrasound machines usingsmall parts probes of frequencies between 10–12 MHz. Sector or linear scanning is carried out withthe patient lying supine, in which position the headis supported, making it easier to remain still.Gravitational pull is exerted in the direction ofthe optic axis, enabling a detached vitreous stillsuspended from the vitreous base, or sedimentationof blood to be readily assessed. Each eye is imagedwhile static and, if possible, during eye movementswith the patient deviating the eyes to the right andleft side, during which pathological structures areobserved,8 such as vitreo-retinal adhesions, detach-ments and membranes. Characteristics of the typeof mobility of these structures help identificationand diagnosis, the vitreous gel moving as acomplete body, but the detached retina undulatingas a membrane. Movement is not possible withsome injured eyes, limiting the examination andmaking diagnosis less straightforward. Completevisualization of the ocular contents is achieved bytransverse and longitudinal imaging, and angulationof the transducer.

Ultrasound has a limited role in the detection offoreign bodies, secondary to plain films and CT with3 mm contiguous sections in axial and coronalplanes through the orbit, supplemented by coronaland sagittal reconstructions when necessary.9

When globe rupture is sought, 2 mm axial andcoronal high-resolution CT is carried out in additionto ultrasound.

Types of injury

There are two main types of ocular injury whichrender the media opaque to ophthalmoscopy: bluntand penetrating, although both may occursimultaneously.

Blunt injuries

These characteristically cause a spectrum ofdamage, involving multiple intra-ocular structures,

Figure 1 Normal horizontal ultrasound image.

Figure 2 Illustrated section of eye.

J.A. Fielding302

due to compression of the anteroposterior (AP)diameter of the eye and corresponding expansion ofthe equatorial plane. Differential elasticity of thevitreous causes traction at the posterior part of thevitreous base, with retinal tearing (dialysis).Severe, blunt injury may cause extensive intra-ocular haemorrhage, retinal tearing and scleralrupture (Figs. 3–5).

Anterior chamber

Hyphema, itself a cause of media opacification isreadily identified on ultrasound (Fig. 6). The adventof high-resolution, linear array probes has lessenedthe problem of “near-field” artefact, but if thelatter is present, a stand off gel is helpful. Theultrasound biomicroscope, employing frequenciesof 50–100 MHz has been used in some centres toimage abnormalities of the anterior segment, suchas corneal oedema, the depth of the chamber, thestate of the angle and the position of the lens.10

Lens dislocation or disruption

Posterior dislocation (Fig. 7) and occasionallyanterior or lateral dislocation is seen. The dislo-cated lens or its nucleus is seen as the normal ovalshape, and is usually mobile with eye movements. Itis more readily identified if a cataract has formed. Ifrupture of the posterior lens capsule occurs withextrusion of lens material into the anteriorvitreous, the lens material is less easy to identify.Lens dislocation resulting from injury is relativelycommon, a series of 71 consecutive cases of oculartrauma containing 12 displacements.11 Posteriordislocation produces few immediate complications,but if surgery is required (e.g. with the onset of

lens-induced uveitis) vitrectomy techniques areundertaken.

Vitreous haemorrhage

This hampers examination by direct vision. Duringthe first 24 h after vitreous haemorrhage, only a fewlow-amplitude reflections are seen, reflectivityincreasing markedly over the next few days.11

Ultrasound is very sensitive for the detection ofvitreous haemorrhage and even small bleeds can be

Figure 3 Blood-filled globe, ruptured with tear (arrow),after impaction of champagne bottle cork.

Figure 4 CT globe rupture (arrow).

Figure 5 Enucleated specimen showing rupture (arrow).

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identified as scattered reflections in the vitreouscavity. With some penetrating injuries, a track ofhaemorrhage is identified, outlining the route ofpassage of a foreign body (Fig. 8). The vitreous isfirmly attached anteriorly at the pars plana andciliary processes, less firmly at the optic disc, andelsewhere lies in free contact with the retina.Detachment therefore takes place posteriorly.

Eyes with opacified media are examined todetermine the severity and extent of vitreoushaemorrhage, and any coexistent abnormalities,for example retinal tear, retinal detachment orchoroidal detachment (Fig. 9). Dense vitreoushaemorrhage obscuring fundus details carries aguarded prognosis. Identification of other latent

injuries is not easy if vitreous haemorrhage issevere, because of the juxtaposition of reflectiveblood and detached coats. Uncomplicated vitreoushaemorrhages are followed up at 4 week intervalsto check for clearing (reduction in vitreous opa-cities) or for membrane formation, (Fig. 10), or thedevelopment of retinal detachment (Fig. 11) whichrequires surgery. Mobile linear opacities and fibri-nous membranes within the gel have been termed“arranged” rather than “organized”, the latterterm implying fibrovascular invasion, which occursrarely in uncomplicated vitreous haemorrhage.8

In animal experiments vitreous haemorrhage hasbeen shown to remain as a discrete blood clot forabout 4–6 weeks, after which it reduces in size.12

The presence of blood exerts severe destructive

Figure 6 Hyphema. Blood clot in anterior chamber(arrow).

Figure 7 Displaced lens (arrow).

Figure 8 Track from perforating injury (arrow).

Figure 9 Choroidal detachment (arrow).

J.A. Fielding304

effects on gel structure; including posteriorvitreous detachment, liquefaction of the gel, theformation of fibrinous vitreous membranes and theformation of a pseudocapsule around the clot.Small haemorrhages can remain unresolved forseveral weeks. No fibrosis occurred in the rabbitvitreous, even with longstanding residual blooddeposits, and it has been suggested that fibrosis(with tractional retinal detachment) is an unusualsequel to uncomplicated vitreous haemorrhage, theformer occurring in ocular diseases in whichvitreous haemorrhage may be an incidental occur-rence (e.g. ocular trauma, diabetic retinopathy).Experimentally, vitreous fibrosis followed atraumatic injection procedure involving perforationof the retinal layers, and sometimes occurred with anassociated retinal detachment.13 The retinal tearsassociated with trauma are thought to be the catalystfor development of vitreous and retinal fibrosis.

Fibrinous vitreous membrane

It is important to document the development ofmembranes in persistent vitreous haemorrhage,especially with vitreo-retinal adhesions, which mayrequire vitrectomy.8 The fibrinous membranes areinitially very mobile on dynamic imaging, butbecome less so with the passage of time. Theymay mimic retinal detachments, and particularcare must be taken when examining to differentiatethese conditions. Fibrinous membranes are usuallyfiner than a detached retina, and move with thevitreous gel on dynamic imaging, lacking the firmanatomical attachments of the retina. An ochremembrane may be formed by sedimentation oferythrocytes on the vitreous surface (Fig. 12), alsorequiring care to differentiate from retinal detach-ment. Vitreous membranes have a lower reflectivitythan the detached retina, and are more mobile,usually without attachment to the optic disc.

Some ophthalmologists use quantitative A-scanning to differentiate between vitreous mem-brane and retinal detachment, especially if themembrane does attach at the optic disc. Standar-dized A scanning is a method developed by Ossoinig,quantifying the differing reflectivity of intra-ocularstructures compared with scleral reflectivity.14 –16

Nevertheless, the usefulness of the A scan isundermined by the overlap zone, as some thickmembranes are more reflective than the detachedretina, and an atrophic retina may be less reflectivethan a membrane. Some workers therefore nolonger use the A scan for diagnostic purposes.17

Retinal tears

Retinal tearing is a precursor of retinal detachment,

Figure 12 Ochre membrane (arrow).Figure 11 Retinal detachment and vitreo-retinaladhesion (arrow).

Figure 10 Fibrinous membranes.

The assessment of ocular injury by ultrasound 305

and the majority of tears or breaks are caused byblunt injuries occurring at the time of impact. Tearsare typically situated at areas of maximum scleraldisplacement, either in the region of the vitreousbase or at the point of impact. Cooling1 in 1987stated that the vitreous base is avulsed in approxi-mately 25% of all cases of contusion detachment.Visualization of breaks or tears by ophthalmoscopyis frequently hampered by intra-ocular haemor-rhage. They are also difficult to see on ultrasoundunless substantial, and appear as short, reflective,linear structures, projecting into the vitreous cavitywith an abrupt termination (Fig. 13). They areeasier to demonstrate when there is less intra-ocular disruption and when not surrounded by densevitreous haemorrhage. Penetrating injuries maycause tears, for example a piercing injury from asharp object (Fig. 14).

Retinal detachment

The aim of scanning soon after injury is either toidentify retinal detachment that has alreadyoccurred, so that treatment may be instituted, orto carry out follow-up ultrasound in severe vitreoushaemorrhage to ensure retinal detachment doesnot develop. Retinal detachment is readily diag-nosed on ultrasound, the complete detachmentappearing as a “V” shape in the vitreous cavity dueto the retina maintaining firm anatomical attach-ments anteriorly at the ora serrata and posteriorlyat the optic nerve head (Fig. 15). Normally, a clearzone is seen between the retinal detachment andthe coats, but with subretinal haemorrhage, reflec-tive fluid is seen in this compartment. Partialdetachment shows as a linear membrane, usuallyextending to the optic nerve head, but not across itas with vitreous membranes. Recent detachments

have an undulating type of mobility on dynamicscanning, but more longstanding detachments dis-play a “flapping” type of motion in the early stagesof proliferative vitreo-retinopathy, before progres-sing to the rigid “triangle sign”. The appearances oftractional retinal detachment due to developmentof fibrous membranes are described later.

Sometimes an unpredictable latent intervaloccurs between injury and the development ofretinal detachment, the latter being delayed andslowly progressive. This is because the majority ofinjuries occur in young people with healthy gelsthat do not readily detach and lose volume, thus

Figure 13 Retinal tear (arrow).

Figure 14 Short tear (arrow).

Figure 15 Shallow retinal detachment with posteriorvitreous detachment.

J.A. Fielding306

providing support for the retina. Most retinaldetachments caused by blunt injury are managedby standard repair techniques with cryotherapy andexplants to support the anterior retina. Vitreousopacities, giant tears and posterior tears aretreated by vitrectomy and gas tamponade.

Choroidal injury

Choroidal tears, haemorrhage and detachment(choroidal detachment) result from severe bluntinjury. The diagnosis is readily made with ultra-sound, the detached choroid showing as a convexindentation into the vitreous cavity, due to thechoroid maintaining firm anatomical attachmentsanteriorly at the scleral spur and posteriorly at theexit foramina of the vortex veins (Fig. 16).Complete choroidal detachment indicates a poorprognosis, and if associated with vitreous haemor-rhage and suprachoroidal haemorrhage, the reflec-tive blood renders the imaging of detached coatseither difficult or impossible.

The diagnosis of incomplete choroidal detach-ment is sometimes useful in alerting the surgeon tothe possibility that his instruments may enter thesuprachoroidal space rather than the vitreouscavity.

Choroiditis with choroidal thickening sometimesoccurs in eyes after perforating wounds (Fig. 17).This complication is tenacious and persistent,heralding the onset of ocular atrophy. It has alsobeen reported occurring transiently in eyes aftersurgery.18 Clinically the eye shows a low-gradeinflammation, with choroidal thickening andoedema of the optic disc and macula. On ultra-sound, the choroid is swollen, and may be measured

by the electronic callipers, demonstrating anincrease above the normal 1 mm thickness.

Globe rupture

Eyes clinically suspected of rupture are examinedwith an extremely gentle technique during ultra-sound examinations, to prevent expulsion of ocularcontents. Blows to the antero-lateral aspect of theeye, which is relatively unprotected by the orbitalwalls, have a higher frequency of globe rupture.Compression of the AP diameter of the globe resultsin corresponding expansion of the equatorial plane,with equatorial scleral rupture. Ultrasound findingsare distortion of the normal global shape with lossof ocular volume, intra-vitreal haemorrhage and

Figure 17 Choroidal thickening.

Figure 18 Blood-fluid level and rupture (arrow).

Figure 16 Subchoroidal haemorrhage.

The assessment of ocular injury by ultrasound 307

scleral discontinuity (Fig. 18). The latter is not easyto identify, and is more readily confirmed by CT(Figs. 4 and 5), when 2 mm axial high-resolution CTis carried out, followed by sagittal and coronalreconstructions if the diagnosis is not made in axialexaminations (Fig. 19).

Clinically, intra-ocular pressure measurementsby tonometry are an indication of rupture but arenot always accurate. Using imaging to identify andconfirm the scleral rupture is useful for surgicalplanning, in difficult cases. Ruptures extendingposterior to rectus muscle insertions have a poorprognosis, with the development of expulsivechoroidal haemorrhage or retinal prolapse.

Penetrating injuries

Penetrating injuries cause a wide spectrum ofdamage, and ultrasound helps to determine theextent and severity of initial structural disruption;particularly vitreous haemorrhage, vitreousincarceration, posterior vitreous detachment,vitreo-retinal adhesion and retinal tears (Fig. 8).Penetrating injuries are frequently caused by thepassage of foreign bodies, or piercing by sharpobjects, some resulting in double penetration of theglobe with major contusional damage and poorvisual outcome.

Foreign bodies

High-velocity foreign bodies result in double pen-etration of the globe; entry and exit points oftencausing severe contusion, vitreous laceration andimpaction. Vitreous incarceration is carefullysought after penetrating injury (Fig. 20), becauseof the high risk of development of vitreousmembranes and tractional retinal detachment,

unless pre-empted by early surgical intervention,with vitrectomy and severance of vitreo-retinaladhesions.

Ultrasound has a limited role in the detection oforbital foreign bodies, because a large proportionof retrobulbar tissue is highly reflective fat. Manyforeign bodies are also reflective and easily lost inthe orbital “white-out”.19 Clinical management offoreign bodies is dependent on the composition andsite. Intra-ocular foreign bodies are usuallyremoved surgically (Fig. 21), to prevent compli-cations from chemical reactions (e.g. siderosis fromiron) or infection. Extra-ocular foreign bodies aremanaged conservatively, and it is therefore import-ant to accurately differentiate between intra-ocular and extra-ocular locations. This is readilyachieved by CT (Fig. 22), although ultrasonographyis superior in the assessment of intra-ocular

Figure 19 Sagittal CT Globe rupture (arrows).

Figure 20 (a) Vitreo-retinal adhesion from passage ofpellet (arrow). (b) Lacerated vitreous (arrow).

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soft-tissue damage. However, ultrasound is lesssensitive than CT in the demonstration of foreignbodies in the globe.20,21 It has been stated that CT isthe investigation of choice, following plain radi-ography in cases of suspected ocular injury.22,23

Nevertheless, CT is unable to resolve subtle intra-ocular soft-tissue damage24 such as vitreo-retinalimpaction or adhesion (Fig. 20), and the examin-ation cannot be carried out in real-time, which isnecessary for identification of these features. CTmust always be used judiciously, as high-resolutionCT delivers a significant dose of radiation to theorbital contents, particularly the lens.25 The mostuseful sequence of investigation of orbital foreignbody is therefore, plain films (to confirm thepresence of a foreign body and identify others),CT to localize the foreign body, then ultrasound todetermine associated intra-ocular injury.

Some investigators recommend MRI in suspectedwooden foreign body in the orbit, if no foreign bodyhas been defined on plain films, ultrasound or CT.Green et al.26 described two patients where theseinitial examinations showed no evidence of aforeign body, but subsequent MRI delineated awooden orbital foreign body in each case. Hydratedand dry wooden foreign bodies exhibit differing CTand MRI characteristics, due to varying watercontent.9,27,28

There is a theoretical risk of orbital or oculardamage when imaging foreign bodies made offerrous metal with MRI. However, in a studyinvolving insertion of both ferrous and non-ferrousmetals foreign bodies in bovine eyes, Williamsonet al.29 accurately located the foreign bodies withMRI, and subsequent dissection revealed no oculardamage attributable to movement of the foreignbodies in the magnetic field. It has been stated thatthe risk of eye damage is low for patients with intra-orbital metal,30 a position refuted by others.31

Nevertheless, MRI is not always readily availableand is still a costly investigation compared with theother imaging methods.

Vitreous incarceration

This is an important complication of penetratinginjury. At the site of penetration, the vitreousbecomes impacted into the retina, forming a vitreo-retinal adhesion (Fig. 20). The retina is breached,initiating the development of fibroplastic (ratherthan fibrinous) vitreous membranes, which, if nottreated early, later contract to form a tractionalretinal detachment.13 Vitreous incarceration isinferred if ultrasound demonstrates asymmetricsuspension of the gel or impaction at the site of

Figure 21 Steel in coats (arrow).

Figure 22 Pellet in orbit (arrow).Figure 23 Triangle sign in proliferative vitreo-retino-pathy.

The assessment of ocular injury by ultrasound 309

penetration through the coats, at the terminationof a laceration or haemorrhage track. The routetraversed by a foreign body (usually at highvelocity) must be carefully sought, as widelydiffering appearances are found in different sec-tions through the globe.

Proliferative vitreoretinopathy and tractionretinal detachment

Blunt injuries resulting in retinal tearing andpenetrating injuries causing retinal holes bothrisk development of rhegmatogenous retinaldetachment (i.e. with a break or hole). If leftuntreated there is a proliferation of fibroplasticmembranes on surfaces of the detached retina, andon the posterior surface of the detached gel.32

Ultrasound shows the shortened, rigid retinalsurfaces with a transvitreal membrane formingthe “triangle sign” (Fig. 23). Dynamic imaging

gives a vivid demonstration of the fixity of thesestructures. Advanced proliferative vitreo-retino-pathy is a difficult surgical prospect, contractionof the fibrotic membranes with further retinalelevation being the most important cause offailure, in retinal reattachment surgery. The manydiffering surgical techniques are an indication ofgenerally unsatisfactory results.3 –6

At the opposite end of the spectrum, certainearly post-traumatic changes also give “V”-shapedappearances on ultrasound, with entirely differentcharacteristics and prognosis (Fig. 24). Shallowtractional retinal detachment is caused byvitreo-retinal adhesion, dynamic imaging showinggreat mobility of the collapsed vitreous. If leftuntreated, a full-blown tractional retinal detach-ment develops (Fig. 25), an occurrence preventedby early intervention by vitrectomy.

Intra-ocular air

The presence of intra-ocular air is a pitfall for the

Figure 24 Early tractional retinal detachment.

Figure 25 Vitreo-retinal adhesion (arrow).

Figure 26 Air bubble (arrow).

Figure 27 CT air bubble (arrow).

J.A. Fielding310

unwary when interpreting the ultrasound findingsafter a penetrating injury. The tissue–air boundaryis highly reflective and a small air bubble appearson ultrasound as a dense, reflective body in thevitreous, thus mimicking or masking a metallicforeign body.33 If the head is tilted an air bubblewill float in the opposite direction, but this is notalways easy to demonstrate (Fig. 26). However, airpockets are clearly shown by CT if an immediatediagnosis is required (Fig. 27). If not, a repeatultrasound in a day or two will show resorption ofthe air. With foreign bodies, adherence to thecorrect investigative sequence of plain films, CTthen ultrasound, ensures that the radiologist isalerted to the presence of intra-ocular air beforethe ultrasound examination.

Conclusion

Ultrasound is a gentle, non-invasive and rapid wayof assessing intra-ocular damage caused by bluntand penetrating trauma, when the media have beenrendered opaque to ophthalmoscopy. The imagesprovide essential, detailed information about soft-tissue damage, aiding decisions regarding earlysurgery, before chronic changes have occurred.

In the investigation of foreign bodies andassociated intra-ocular injuries, the sequence ofplain films, CT, then ultrasound (followed by MRI ifa wooden foreign body is still suspected) provides alogical method of examination, ensuring detectionof ocular and orbital foreign bodies and intra-oculardamage, whilst helping the unwary to avoid thepitfall of misdiagnosing intra-vitreal air.

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