The ocular examination in scleral diseases must include an episcleral and scleral examination and a general ophthalmologic examination. The episcleral and scleral examination should be performed under conditions of daylight and with the slit lamp, employing diffuse, white light, the narrow slit beam, and red-free illumination.
Episcleral and scleral examination in daylight is sometimes the only way to distinguish episcleritis from scleritis, as the natural color of the sclera is not distorted. In episcleritis, the eye appears pink to red; in scleritis, the eye has a deep bluish-red or violaceous tinge. If scleral necrosis is present, blue-gray to dark-brown areas corresponding to the underlying uvea may become visible through the translucent sclera. If tissue necrosis is progressive, the scleral area may become avascular, producing a central white sequestrum surrounded by a well-demarcated black or dark-brown circle. The slough may be gradually replaced by granulation tissue, leaving the underlying uvea bare or covered by a thin layer of conjunctiva.
Slit-lamp examination under conditions of diffuse illumination helps to detect congested vessels, nodules, or avascular areas with sequestra or visible uveal “show-through.” It also helps to differentiate the configuration of vessels; in episcleritis, congested vessels follow the usual radial pattern while in scleritis this pattern is altered and new, abnormal vessels are formed. Slit-lamp examination with the narrow slit beam is used to detect the depth of inflammation, indicating which network of vessels is predominantly affected. In episcleritis, maximum congestion is observed in the superficial episcleral network, with no changes in the deep episcleral network. The edema is localized to the episcleral tissue. The anterior edge of the narrow slit beam is displaced forward while the posterior edge remains flat against the sclera, in its normal position. Topical application of 10% phenylephrine renders the eye white as its vasoconstrictor effect is greater on the superficial episcleral plexus, having no significant effect on the deep episcleral vessels (Figures 6a, 6b). In scleritis, maximum congestion is seen in the deep episcleral plexus, although the overlying superficial episcleral plexus is not infrequently involved as well. The edema is localized to the scleral and episcleral tissues. The anterior and the posterior edges of the narrow slit beam are displaced forward. As topical application of 10% phenylephrine only blanches the superficial episcleral plexus and not the deep episcleral plexus, the eye remains congested in scleritis. Red-free light is helpful in revealing areas of maximal vascular congestion, avascularity, and new vascular channels.
Evaluation of adjacent structures should be performed at every follow-up visit for a patient with scleritis. Keratitis, uveitis, glaucoma, cataract, or fundus abnormalities may lead to vision loss and, in some cases, destruction of the eye.