A 21-Year-Old With Headache and Blurred Vision

Discussion

Posterior scleritis is a rare condition that can mimic many ocular inflammatory and neoplastic conditions.^[1] As its name implies, it is an inflammation of the sclera and episclera of the postequatorial segment of the eye.

Posterior scleritis is a difficult disorder to diagnose because of its low incidence, location, and variable clinical presentation.^[1] It must be considered as part of the differential diagnosis of many ocular conditions, including angle-closure glaucoma, choroidal folds, optic disc edema, circumscribed fundus mass, choroidal detachment, exudative retinal detachment, and even carotid cavernous fistula.^[2,3,4]

Posterior scleritis is typically unilateral, with an average age of onset of 50 years.^[5,6] It affects twice as many women as men, more adults than children, and more white persons than nonwhite persons.^[6,7] The older the patient with posterior scleritis, the more likely he or she is to experience vision loss.^[6] All patients with posterior scleritis are at risk for permanent loss of vision; therefore, early treatment is essential to control the inflammation and preserve the vision.

The symptoms and signs of posterior scleritis depend on how far the inflammation spreads. Inflammation can remain localized to a specific area of the posterior segment, as is the case in nodular posterior scleritis, which can resemble a choroidal melanoma.^[8] Inflammation can also spread anteriorly and mimic orbital cellulitis.^[9] The anterior segment is not always involved; therefore, external signs of inflammation, such as red eye, may not be noted. A reduction in visual acuity and abnormal visual fields may or may not be present.^[3,6,7] Inflammation from posterior scleritis can also involve other orbital structures.

Diplopia can occur if the inflammation restricts eye movement.^[5] Most patients will experience some degree of pain, from pain on eye movement to pain that prevents them from sleeping. This pain may radiate to the surrounding structures, such as the brow and jaw.^[5,7] Anterior or posterior uveitis is present in 70% of cases.^[7] Shallowing of the anterior chamber and glaucoma can also be present.

The most common fundus signs are optic nerve swelling, serous detachment of the retina with macular edema, subretinal mass, and choroidal folds concentric to the margins of the retinal mass. Intraretinal lesions resembling hard exudates, as well as pigment epithelial elevations and mottling of the pigment epithelium, have all been reported with posterior scleritis.^[7]

Because no classic signs or symptoms are associated with posterior scleritis, it is imperative that ancillary testing be performed. B-scan ultrasonography is perhaps the most important diagnostic tool in confirming the diagnosis of posterior scleritis.^[10] Therefore, ultrasonography should be performed on all patients with choroidal folds in which the diagnosis is not certain.^[6] Posterior scleritis is seen as a flattening and thickening of the posterior of the eye wall (> 2 mm is considered abnormal).^[2,11] Edema is present in the Tenon space.^[12] A T sign, formed by the squaring of the normally rounded optic nerve shadow, along with edema that extends along with adjacent sclera, may be present.^[4,13,14] The T sign may be absent in mild posterior scleritis.^[14]

Fluorescein angiography is valuable in distinguishing between central serous retinopathy and choroidal melanoma, 2 of the possible differential diagnoses.^[14] Posterior scleritis may show blocked fluorescence in the initial arteriovenous phase and diffuse hyperfluorescence in the late phase, with no leakage. Choroidal folds may be seen on fluorescein angiography as alternating hyperfluorescent and hypofluorescent bands, distinguishing them from retinal striae.^[14]

With the advent of OCT, the details of the retinochoroidal structures can be visualized in cross-section, showing the inflammation caused by posterior scleritis. OCT can show any potential serous detachment or other retinochoroidal structural changes that may be present.^[8] The presence of choroidal folds will be noted by a wavy appearance of the retina-choroidal complex.^[15] The OCT is perhaps more important than fluorescein angiography in diagnosing posterior scleritis and monitoring the treatment.^[16]

CT and MRI, with and without contrast, can also be used to visualize the characteristic scleral thickening and a T sign.^[17] However, because of its higher resolution capacity, ultrasonography is preferred over CT.^[1]

Orbital pseudotumor can produce similar findings on ultrasonography and CT, but without the presence of anterior uveitis, optic disc edema, subretinal mass, and choroidal folds. In some cases, CT or MRI is useful to help differentiate posterior scleritis from orbital inflammation and neoplasms, extraocular muscle, or lacrimal gland enlargement.^[18] These tests are important to obtain, especially when a proptosis is present or if carotid-cavernous fistula is suspected.^[4,19]

Posterior scleritis is predominantly idiopathic or autoimmune.^[20] In a retrospective review, McCluskey and colleagues^[6] found that 29% of patients had associated systemic diseases, including systemic vasculitis, lymphoma, and autoimmune disease; the most common was rheumatoid arthritis.^[6,11,19] On rare occasions, especially when it is an extension of an anterior scleritis, the causative agent may be infective. Many types of bacteria, fungi, and parasites have been associated with scleritis, usually after some predisposing factor, such as cataract surgery, scleral buckling surgery, pterygium surgery, suture removal, scleral buckle removal, or trauma. Posterior scleritis can also follow systemic infection.^[21]

A full work-up is important in patients with posterior scleritis to rule out systemic etiology. This can include rheumatoid factor; antinuclear antibodies; antineutrophil cytoplasmic antibodies; HLA typing; eosinophil count/immunoglobulin; erythrocyte sedimentation rate; hepatitis B surface antigen; serologies for infectious diseases, such as syphilis and Lyme disease; purified protein derivative; anergy skin testing; and chest, sinus sacroiliac, and limb radiographic studies.^[18]

A potential complication of posterior scleritis is ciliochoroidal effusion syndrome (uveal effusion syndrome). This refers to an abnormal collection of fluid between the sclera and the choroid or ciliary body that expands the suprachoroidal space, thereby producing internal elevation of the choroid. In the case of ciliochoroidal effusion syndrome, it is important to relieve the iris compression of the angle by displacing the lens iris diaphragm posteriorly with the use of cycloplegics.^[20]