diagnostic tool for evaluation.36 B-scan evaluation reveals moderate to dense, diffuse vitreous opacities with moderate mobility (Fig. 5). Vitreous inflammatory debris cannot be differentiated accurately from diffuse vitreous hemorrhage with B-scan, and therefore ultrasonographic findings must be used in conjunction with other clinical findings.

Panuveitis

Panuveitis refers to inflammation involving the anterior chamber, vitreous, retina, and/or choroid, generally secondary to a systemic disease.6 Many systemic infectious and noninfectious diseases (eg, syphilis, Lyme disease, tuberculosis, sarcoidosis, Behc¸ et’s disease, Vogt-Koyanagi-Harada syndrome, and sympathetic ophthalmia) are associated with panuveitis. The prevalence is as high as 22% in tropical countries, but in North America it ranges between 9% and 18% of all cases of uveitis. Some cases of lens-induced uveitis, toxoplasmosis, or toxocariasis may begin as anterior or posterior uveitis and progress to panuvei-

tis.8,14,18,34,37–39

SYMPATHETIC OPHTHALMIA AND VOGT-KOYANAGI-HARADA SYNDROME

Sympathetic ophthalmia is a bilateral granulomatous panuveitis that usually begins after penetrating trauma with uveal prolapse in one eye (the exciting eye) leading to inflammation in the fellow unaffected eye (the sympathizing eye).40,41 Very rarely, nonpenetrating procedures such as laser photocoagulation, cryotherapy, and radiation have been associated with sympathetic ophthalmia.41 The incidence of sympathetic ophthalmia is estimated to be 0.2% to 0.5% after penetrating injuries and around 0.01% following intraocular

surgery. The pathogenesis is not understood clearly.42 Cataract, inflammatory membranes, and serous retinal detachment may develop in some cases.43

In Vogt-Koyanagi-Harada syndrome the appearance of the fundus can resemble sympathetic ophthalmia. Vogt-Koyanagi-Harada syndrome is a rare cause of granulomatous panuveitis that most commonly affects persons of Asian or American Indian ancestry between 30 and 50 years of age.44

B-scan ultrasonography of the posterior segment can evaluate and differentiate the pathology associated with panuveitis, including vitreous membranes, retinal detachments, and choroidal thickening. This information may be used to determine and monitor therapeutic options (see the article by Sharma and colleagues, elsewhere in this issue). Sympathetic ophthalmia and Vogt-Koyanagi- Harada syndrome exhibit similar echographic findings. The most common findings include serous retinal detachments and diffuse, low-to- medium reflective choroidal thickening (Fig. 6).45 In the absence of clear media, B-scan imaging can be used to monitor response to corticosteroid treatment by evaluating the elevation and extent of retinal detachments and choroidal thickness. Additionally, UBM may show features that are not obvious clinically, such as uveal ciliary body changes and thickening.46

SCLERAL INFLAMMATORY DISEASE

Episcleritis

Episcleritis is a noninfectious inflammatory condition affecting the episcleral tissue, the layer that lies between the conjunctiva and the sclera. It usually presents as redness in one or both eyes. There may be a sector of redness, or the redness may be diffuse throughout the surface of the eye. Occasionally, there may be a nodule in the center of

the inflamed area (nodular episcleritis). Some patients may complain of mild pain or tenderness to the affected region, but more commonly there is no discomfort.47–52 Topical vasoconstricting agents are used most commonly to differentiate episcleritis from scleritis. When episcleritis is severe, the underlying scleral tissue may be obscured, and UBM examination may be indicated.53,54 UBM imaging provides a clear distinction between low-to-medium reflective episcleral tissue and very high reflective scleral tissue (Fig. 7).

Scleritis

The sclera consists of collagen fibrils that are arranged in an interlacing manner. Sclera is relatively inert metabolically but has important functions such as protection, opacity (vital to retinal function), eye movement, and maintenance of intraocular pressure.47,55,56 Scleritis is a serious, potentially blinding inflammation of the sclera. Unlike episcleritis, which may be asymptomatic or associated with minimal discomfort, scleritis presents with severe, boring ocular and periocular pain and can be associated with light sensitivity,

tearing, and decreased vision. Scleritis may present as sector or diffuse redness and can be of infectious or inflammatory origin.47,49,55–57

Anterior scleritis

Anterior scleritis is the most common form of scleritis. Diffuse anterior scleritis is characterized by extensive edema and scleral tissue congestion with poorly defined margins. The adjacent episclera and conjunctiva may be involved also. UBM can be useful in the evaluation and differentiation of anterior scleritis by defining the involved area and identifying regions of necrosis and scleral thinning or nodular lesions.53,54 Ultrasonography reveals episcleral thickening and an irregular sclera with mottled areas of lower reflectivity within the sclera (Fig. 8A, B).

The nodular form of anterior scleritis has congestion and scleral nodules that are evident clinically. UBM can define the involved borders,

Fig. 6. Vogt-Koyanagi-Harada syndrome. Axial B-scan showing marked choroidal thickening (arrow) and a serous retinal detachment (arrowhead).

most importantly the low-reflective intrascleral involvement that cannot be observed externally (Fig. 8C, D).

The third type of scleritis, necrotizing scleritis, is characterized by scleral necrosis.57 In severe cases of necrotizing scleritis, the sclera may become very thin and transparent, and the underlying layer, the dark choroid, can be seen. Patients also may develop inflammation of the cornea (peripheral keratitis) and inflammation in the anterior chamber (secondary uveitis).49,50,57 UBM provides accurate measurements of scleral thickness in areas of concern and may be used to determine therapeutic or surgical intervention. Rarely, anterior scleritis may be the presenting sign of an occult metastasis to the ciliary body.58,59 In suspected cases, UBM should be used to rule out the presence of an underlying lesion/mass (Fig. 9).

Posterior scleritis

Posterior scleritis can be a diagnostic challenge because of its variable clinical presentation, including serous retinal detachment, chorioretinal lesions, retinal pigment epithelial changes, or even a quiet fundus. It can occur concomitantly with anterior scleritis or separately. Symptoms can be similar to those seen in anterior scleritis or have no anterior symptoms or signs. B-scan ultrasonography is an essential tool for the accurate diagnosis of posterior scleritis, most frequently revealing the classic T-sign, which represents thickened posterior sclera with underlying fluid collection in Tenon’s space (Fig. 10A). Although the T-sign often is present, marked scleral thickening consistent with posterior scleritis may be present in the absence of associated inflammatory edema (Fig. 10B).