Diagnosis of scleritis is based on a detailed clinical history, close inspection, and slit-lamp and fundus examination. Sometimes it may be easier to appreciate scleritis by looking at the eye externally without the slit lamp. Complementary B-scan ultrasonography, fundus angiography, and optical coherence tomography (OCT) can help better delineate scleral involvement. An appropriate laboratory workup is warranted to rule out underlying systemic inflammatory diseases (Table 7-2), which may be very frequent and life-threatening, especially in the setting of necrotizing scleritis. Finally, it is important to consider the possibility of drug-induced scleral inflammation (mainly associated with bisphosphonates).
B-scan ultrasonography is useful for confirming suspicion of posterior scleritis or assessing concomitant posterior scleral involvement. Imaging typically reveals thickening of the sclera, associated with accumulation of fluid in the sub-Tenon space. When adjacent to the optic nerve shadow, this may lead to the classic “T-sign” (see Fig 7-9). Ultrasonography may also be helpful to assess involvement of adjacent structures, including the choroid, ciliary body, retina, extraocular muscles, and orbit. Computed tomography (CT) and magnetic resonance imaging (MRI) can also assist in the assessment of orbital structures in posterior scleritis.
Posterior segment spectral-domain optical coherence tomography (SD-OCT), including enhanced depth imaging (EDI), may also be useful to delineate fundus changes associated with posterior scleritis (see Fig 7-9). Anterior segment SD-OCT may provide noninvasive imaging that documents local changes at the level of the sclera, episclera, Tenon capsule, conjunctiva, cornea, and angle structures, but its clinical utility is unclear at this time. Ultrasound biomicroscopy may be used to image the anterior segment and ciliary body, but this technique is often technically cumbersome in tender and painful eyes with scleritis. In cases of posterior scleritis, fundus fluorescein or indocyanine angiography can identify the extent of disease and may be helpful in differential diagnosis.
Table 7-2 Investigations for Noninfectious Inflammatory Conditions Associated With Scleritis
In the setting of high suspicion for infectious scleritis, microbiological examination of scleral scrape and even incisional biopsy of the sclera can be very helpful. Biopsy is also valuable in the possibility of neoplastic conditions, such as conjunctival carcinomas and lymphomas. These can masquerade as or even be associated with a variable degree of scleral inflammation. Intraocular tumors, particularly large uveal melanomas, occasionally lead to engorgement of overlying episcleral (so-called sentinel) vessels.
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Excerpted from BCSC 2020-2021 series: Section 9 - Uveitis and Ocular Inflammation. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.