Ординатура / Офтальмология / Учебные материалы / Uveitis Text and Imaging Text and Imaging Text and Imaging 2009

Figure 5: Photograph showing scleral cup applied on eye while acquiring scans

Ultrasound cannot travel in air; the sound waves are transmitted into the eye through the coupling solution held in the scleral cup applied to the eye. Further, it prevents contact between transducer and the eye and avoids distortion of image close to transducer. A constantly moving transducer should not be brought in contact with the cornea as it may result in corneal abrasions. Air bubbles are to be avoided in the coupling agent and on the concave surface of the transducer.

The scans are acquired with the patient lying supine. The scan head is placed directly over the ocular parts to be examined. We can examine any part of the eye i.e. cornea and anterior segment structures, that can be approached from the surface using horizontal and radial scans. Rotating the eye as far as possible can scan the conjunctiva, underlying sclera and peripheral retina. This allows view of the peripheral retina and more so temporally. Pupillary dilatation is not required while acquiring these scans.

Various types of ocular scans acquired are

1.Radial or meridional scans – Radial scans are acquired by keeping the probe along every clock hour perpendicular to the limbus (Figure 6).

2.Longitudinal or Axial scan – Scans are acquired by keeping the probe 90 to the radial line tangential to the limbus thus giving longitudinal scans of various structures (Figure 7).

ANALYSIS AND INTERPRETATION

OF UBM SCAN

The UBM scans can be interpreted objectively and subjectively.

Figure 6: Radial UBM scan taken along every clock hour

Figure 7: Photograph showing UBM scans taken longitudinally i.e. perpendicular to radial scan

OBJECTIVE INTERPRETATION

A large number of anterior ocular tissues can be visualized in living tissue and hence can be compared with the normal to find any ocular pathology. In uveitis, important structures to be examined include iris and cilliary body, pars plana and peripheral retina and retroiridial space.

Iris and Cilliary Body

The iris normally shows variation in thickness. The posterior surface of the iris formed by iris epithelium

Figure 8: Radial UBM scan showing cilliary body, iris, zonules and angle structures

Figure 9: Longitudinal UBM scan showing CB villosities (arrow head) and valley (arrow) between them

Figure 10: Radial UBM scan through the pars plana area

Figure 11: Radial UBM scan showing retroiridial structures

is seen as highly reflective layer. This helps to differentiate intra-iris lesions from the lesions posterior to iris. The cilliary body can be seen clearly on UBM. Radial scans will shows radial image through the processes (Figure 8) and the scans right angles to it i.e. horizontal scan will display variable configuration of the cilliary processes and the valley between them (Figure 9).

Pars Plana and Peripheral Retina

By asking the patient to move the eye in a particular direction, we can examine the pars plicata, pars plana and peripheral retina in that quadrant. Anterior vitreous in adjacent areas can also be visualised (Figure 10).

Figure 12: Radial scan showing a hyper-reflective foreign body in pars plana region

Retroiridial Space

UBM examination can pick up the pathologies in area behind the iris. i.e. misplaced IOL, cysts (Figure 11).

Following lesions are hyper-reflective

a.Foreign bodies (Figure 12)

b.Scars.

Following lesions are hypo-reflective

a.Abscess – Presents as hypo reflective areas in iris or cilliary body in granulomatous inflammation.

b.Serous fluid – In case of cillio-choroidal effusion, there is accumulation of fluid in between sclera and choroid.

SUBJECTIVE INTERPRETATION

UBM has the ability to accurately measure the ocular structures, due to more resolution. Measurements are done on screen using calipers. After acquiring the scan the stored image can be measured using prestored imaging software. UBM allows greater clarification of borders and thus allows more accurate measurement of chamber depth, cilliary body, sclera and iris.

INDICATION OF UBM IN UVEITIS

UBM has been shown of great clinical value in uveitis patients.6 It has been found to be useful in the following situations in uveitis by providing the following information.

IRIS AND CILLIARY BODY PATHOLOGIES

UBM scans of the iris in uveitis can give information regarding the presence of iris nodules with hypo dense center, especially in granulomatous uveitis (Figures 13A and B).

During acute iridocyclitis, the iris and ciliary body become thickened due to swelling with blunting of the ciliary processes. Other findings include the presence of ciliary body ganulomas and angle closure caused by peripheral anterior synechiae and pupillary seclusion. UBM also helps in diagnosing melanoma of ciliary body that may masquerade anterior uveitis. Extensive cilliochoroidal detachment is seen Vogt- Koyanagi-Harada disease.

UBM has been used to detect an intraocular nematode in the iris root in suspected nematode induced uveitis7 and caterpillar hairs causing pars planitis.8

Case Reports

Case # 1

A 57-year-old man suffered from recurrent attacks of acute anterior uveitis with HLA B 27 positivity. He was seen with acute inflammation in the left eye with moderate anterior segment inflammation (Figure 14A). UBM radial scan showed thickening of ciliary body with iris bowing (Figure 14B) with blunting of ciliary processes seen on the longitudinal scan (Figure 14C).

The right eye that was normal showed normal ciliary processes (Figures 14D-F).

One week later, he had recurrence of inflammation in the right eye with appearance of hypopyon (Figure 14G). Repeat UBM done at this stage showed thickening of iris and ciliary body with blunting of ciliary processes (Figures 14H and I).

Case # 2

A 10-year-old boy was seen with hypopyon uveitis (Figure 15A). His laboratory work-up was inconclusive. UBM showed the presence of ciliary body granuloma with hypo dense center in cilliary body stroma showing extension of granuloma in to the anterior vitreous (Figure 15B).

The inflammtion worsened on conservative management with corticosteroids (Figure 15C).

Five days later, the patient underwent left eye pars plana lensectomy with vitrectomy PCR for the vitreous was positive for Mycobacterium tuberculosis and the responded to anti-tuberculosis treatment with a final acuity of 20/30 with contact lens (Figure 15D).

Case # 3

A 45-year-old man was referred as a case of anterior uveitis with cataract (Figure 16A). There was a forward bowing of the iris in the upper-nasal quadrant (Figure 16B). UBM revealed the presence of ciliary body mass that was subsequently confirmed as melanoma (Figure 16C).

CILIARY BODY

Role of UBM in the diagnosis and management of the chronic ocular hypotony has been well reported.9 UBM can clearly show the possible causes of hypotony in the uveitic eyes with or without opaque media. Hypotony can be as a result of cilliochoroidal detach-

ment. Ciliochoroidal detachment leads to reduction in aqueous humour production, when associated with iridocyclitis (Figures 17A and B).

Another reason for hypotony is the presence of a cyclitic membrane (Figures 18 and 19A, B).

Acute inflammation of ciliary body may result in the formation of a suprachoroidal cleft resulting in hypotony (Figures 20A and B).

Cilliary body atrophy as a cause of hypotony can be seen in chronic inflammation (Figures 21A and B).

Knowing the causes of hypotony could help in planning further course of action in these patients. Patients with cilliary body atrophy are the poor

candidates for cataract surgery due to the risk of phthisis bulbi.

PARS PLANITIS

Pars plana imaging by UBM allows us to clearly visualize the pars plana condensations especially in opaque media (Figures 22A and B).

In patients with no fundus view, UBM can be effectively used to look for the presence of pars plana exudates (Figures 23A and B).10,11 It could be useful especially in patients with opaque media to diagnose and monitor treatment response.11

Figures 16A-C: Radial UBM scan showing a hypo reflective area depicting cilliochoroidal detachment in a case with chronic uveitis and hypotony

Figure 18: Radial UBM scan showing a cyclitic membrane (arrow) attached to the ciliary

PSEUDOPHAKIC UVEITIS

Constant Irritation of ocular tissues by an IOL could be the cause of chronic postoperative noninfectious inflammation in pseudophakic eyes (Figures 24A and B). UBM is helpful in detecting the IOL position and its relationships to ocular tissues.12 Sulcus implanted IOL’s are known to cause chronic inflammation. UBM can clearly detect the position of haptic, thus helping in further management in these patients.

TOXAOCARA UVEITIS

Tran et al13 described specific signs for detecting Toxocariasis detection characterized by pseudocystic

degeneration of the peripheral vitreous. Authors reported that UBM was a better and helpful tool to detect Toxocariasis. In another study, UBM was found to be specific and sensitive in patients with a presumed diagnosis of peripheral Toxocariasis.14

SCLERITIS

UBM has characteristic features that help in differentiating episcleritis from scleritis (Figures 25 and 26). UBM can show the extent of the lesion and can be used as follow up tool to show resolution of disease. Thickness, reflectivity, and homogeneity of the sclera and episcleral lesions help in differentiating between

the different types of scleritis and episcleritis. Thickness will help in differentiating scleral thinning from the nodular type of scleritis. Reflectivity and homogeneity of the internal structures will help to pick up scleral necrosis. In case of scleral necrosis, homogeneity will be lost and it will be hypo reflective internally. Superficial lesions with no involvement of the sclera will favor diagnosis of episcleritis.

OPAQUE MEDIA

UBM is a helpful tool in uveitis with opaque media. It can be helpful in detecting any anterior segment pathology i.e. iris or cilliary body granulomas/abscess. It was very useful in cases of opaque media with hypotony. Detection of cause of hypotony in these eyes can help in predicting future course of action.

RELEVANCE OF UBM IN UVEITIS

Most information we have on the use of UBM in uveitis consists essentially of case reports. The global relevance of the method was analysed in a study looking retrospecively at the proportion of cases in a series of uveitis patients that benefited from UBM examination.6 This study looked at the proportion of cases for which UBM gave essential information that allowed to reach a diagnosis or to influenced the management.

UBM was performed in 77 uveitis patients out of a total collective of 612 patients (12.5%). In this biased collective including only cases where UBM was deemed necessary, essential information was obtained in 32 of 77 patients (42%). The categories of patients benefitting most of UBM examination where those with opaque medias (9/9 patients, 100%), patients with hypotony (10/12, 93%) and toxocara uveitis (5/5, 100%, pseudocystic vitreous degeneration) (Figure 27). An illusrative set of cases were two patients showing vitritis and profuse retinal vascular leakage attributed to Behçet’s uveitis in the first case, while UBM clearly showed thick deposits over the pars plana/snowbanking) typical of intermediate uveitis of the pars planitis type (Figure 28). The second case was diagnosed as para planitis but did not show any snowbanks on UBM rendering this diagnosis very unprobable, the final diagnosis being Behçet’s uveitis. (Figure 29).

Figure 27: Pseudocystic aspect of vitreous in toxocara uveitis

Figure 28: Thick depositis over pars plana typical of intermediate uveitis of the pars plana type in a patient disgnosed initially as Behçet’s uveitis

Figure 29: Patient initially diagnosed as pars planitis with absent snowbanking, later diagnosed as Behçrt’s uveitis

DRAWBACKS

Most important drawback of UBM is penetration. It cannot be used for the posterior segment structures because of lack of penetration. UBM requires patient