anastomoses between the larger vessels in the superÞcial or deep episcleral plexuses with extensive leakage may be observed on ßuorescein angiography. These anastomoses may persist and remain permeable for a prolonged period of time even in the absence of inßammation. There is no evidence of vascular closure. In ICG angiography, there is no leakage except in regions of local vascular damage, which may signify accompanying deep inßammation. The Þndings of anterior segment ßuorescein angiography and ICG angiography in nodular scleritis are similar to those found in diffuse anterior scleritis: rapid Þlling, short transit times, and staining of the nodules in both techniques.

In necrotizing scleritis, anterior segment ßuorescein angiography shows hypoperfusion, venous occlusion, and new vessels that leak extensively. In contrast to nodular scleritis, the transit time in necrotizing scleritis is markedly increased, even in the presence of ocular congestion. With severe inßammation, vaso-occlusive changes in the conjunctival vessels may also appear. ICG angiography also shows hypoperfusion, venular occlusion, increased transit time, and late leakage from new or damaged vessels in addition to providing detailed images of functioning vessels that might be otherwise obscured by edema or leakage of ßuorescein dye. Both ßuorescein angiography and ICG angiography are useful during the early treatment phases to conÞrm the presence or absence of vascular occlusion and to detect active vasculitis.

3.2.8Other Imaging Studies

3.2.8.1 Ultrasonography

Diagnostic ultrasonography consists of the propagation of high-frequency sound waves reßected by interfaces between tissues. The reßected waves create echoes that are displayed on an oscilloscope screen. Ultrasonography is a useful test to detect changes in and around the eye. The main advantages of this method are that it is relatively inexpensive, rapid, produces images in real time, can obtain images in different planes (changing rapidly from one plane to another),

Fig. 3.27 B scan ultrasonagram of a patient with posterior scleritis. Note the marked thickening of the retinochoroid later and the collection of edema ßuid in TenonÕs space

Fig. 3.28 B scan ultrasonagram with associated A scan tracing. Note the obvious retinal detachment in this patient in whom the fundus could not be seen because of dense cataract

and produces no biological hazards. The main disadvantages are the need for direct contact with the globe or eyelid, dependence on operator skills, and inferior spatial resolution and resolving power compared to those of computerized tomography (CT) scanning or magnetic resonance imaging [117].

Ultrasonography is the most helpful ancillary test in detecting posterior inßammation of the sclera, and therefore should always be performed before computerized tomography or magnetic resonance techniques are used. Flattening of the posterior aspect of the globe, thickening of the posterior coats of the eye (choroid and sclera),