bubble_chart Overview

The sclera is a tissue with few cells and blood vessels, mostly composed of collagen. Its surface is covered by the conjunctiva and Tenon's capsule, preventing direct contact with the external environment, so it rarely becomes diseased. According to most scholars, its incidence accounts for only about 0.5% of all eye disease cases. Due to the collagenous nature of the sclera's basic components, its pathological processes are slow, and the resulting collagen disorders are difficult to repair. The eyeball is a "window" for collagen, so scleritis is often the ocular manifestation of systemic connective tissue diseases.

bubble_chart Etiology

The cause of scleritis is often unknown. Sometimes not only the cause cannot be identified, but even the primary site of inflammation—whether it is in the sclera, episclera, Tenon's capsule, or other intraorbital structures—remains unclear. For example, posterior scleritis is difficult to differentiate from acute inflammatory orbital pseudotumor.

(1) Exogenous infection

Exogenous cases are relatively rare and may be directly caused by bacteria, viruses, fungi, etc., through conjunctival infection foci, trauma, or surgical wounds.

(2) Endogenous infection

1. Suppurative metastatic (pyogenic bacteria).

2. Non-suppurative granulomatous (subcutaneous nodules, syphilis, leprosy).

(3) Ocular manifestations of connective tissue diseases

Connective tissue diseases (collagen diseases) are associated with autoimmunity, such as rheumatoid arthritis, necrotizing nodular erythematosus lupus, nodular polyarteritis, sarcoidosis, Wegener's granulomatosis, relapsing polychondritis, etc., which can complicate scleritis. The fibrinoid necrotic changes in the sclera caused by these conditions are essentially similar to those of connective tissue diseases. In necrotizing scleritis, the complication rate is over 50%, and it is even higher in cases of perforating scleromalacia. Other conditions, such as ankylosing spondylitis, Behçet's disease, dermatomyositis, IgA nephropathy, temporal arteritis, and porphyria, have also been reported to complicate scleritis. Watson (1982), through animal experiments on the mechanisms inducing scleritis, pointed out that this type of granulomatous change may indicate that the lesion is caused by locally produced antigens (in type IV delayed hypersensitivity) or the deposition of circulating immune complexes in the eye, triggering an immune response and leading to type III hypersensitivity. In type III hypersensitivity, the vascular reaction results from the binding of antigens and antibodies on the vascular wall. These complexes deposit on the walls of small veins and activate complement, thereby inducing an acute inflammatory response. Therefore, collagen diseases are autoimmune disorders related to individual genetic immune dysregulation or one of their manifestations.

bubble_chart Pathological Changes

Biopsy of scleral membrane lesions is relatively dangerous but frequently performed. Pathological changes can only be studied during enucleation or by examining surgically excised lesion tissues. The infiltrates, thickening, and nodules observed in scleritis represent a chronic granulomatous sexually transmitted disease change, characterized by fibrinoid necrosis and collagen destruction. Except for cases caused by external infections or spread from adjacent suppurative foci, purulent inflammation is rare. Localized inflammation may occur at sites where blood vessels enter or exit.

Granulomatous inflammation can be either localized or diffuse, but its essence remains the same: the affected scleral membrane exhibits chronic inflammatory cell infiltration, including polymorphonuclear leukocytes, lymphocytes, and macrophages, forming nodular or diffusely thickened lesions. The granuloma is surrounded by multinucleated epithelioid giant cells and both new and old blood vessels, some of which show thrombosis, indicating vasculitis. These changes sometimes extend beyond the granuloma, initially affecting scleral membrane mucopolysaccharides far from the lesion, manifesting as weakened colloidal iron staining. In the granuloma area, fibers are displaced by mucoid edema, and mucopolysaccharides only form patchy staining. Under electron microscopy, collagen fibrils are also seen absorbing the stain. Cellular changes here include a significant increase in the number and activity of collagen fibroblasts, while within the granuloma, cellular components markedly increase, with the area infiltrated by plasma cells, lymphocytes, and macrophages, some of which aggregate into giant cells. Scleral collagen fibrils lose their birefringence under polarized light. In necrotic areas, infiltrates dominated by plasma cells are observed, with cellular necrosis and collagen fiber proliferation. In these regions, clusters of new blood vessels originate from the episclera or choroid. Both new and old vessels exhibit medial necrosis, mucopolysaccharide deposition, and thrombosis. Many vessels show fibrin deposition within and around them.

When the lesion is superficial, both the subconjunctival and superficial scleral layers are affected. Scleral edema may show interlayer separation with lymphocyte infiltration in the gaps, while superficial scleral vessels become congested and lymphatic vessels dilate. Mild cases often heal without scarring. Inflammation affecting the anterior sclera may extend to the cornea, and antagonistic hypopyon keratitis can also spread to the sclera, causing episcleritis. Deep scleritis often involves the superficial sclera as well. In necrotizing scleritis, the central lesion area develops fibrinoid necrosis, surrounded by palisading mononuclear cells. In severe cases, patchy avascular areas (stirred pulse occlusion) may form at the center of inflammatory cell infiltration, with tissue degeneration and necrosis, followed by fatty degeneration, hyalinization, or calcification. The necrotic area gradually absorbs and fibroses, forming a scar. This localized sclera may thin and expand or thicken, resulting in so-called "hypertrophic scleritis" (SchÖbl, 1889).

bubble_chart Clinical Manifestations

Based on the site of inflammation invading the sclera or episcleral tissue, symptoms, and prognosis, it is generally accepted that classifying scleritis into the following types is reasonable (Table 1).

Table 1 Classification of Scleritis and Episcleritis

(1) Episcleritis

Episcleritis is an inflammation of the superficial (or outer) layer of the sclera, mostly located in the anterior equatorial region between the limbus and the insertion line of the rectus muscles. It has a history of periodic attacks and leaves no traces after healing. Both adult men and women can be affected, but it is more common in women, and most patients have unilateral involvement.

The cause is often unknown, frequently associated with allergic reactions due to exogenous antigen-antibody interactions, or other systemic diseases such as metabolic disorders—pain wind. This condition often occurs during menstruation in women and is also related to endocrine imbalances. Allergic reactions are more likely to occur in the anterior episclera, which is related to the fact that the episcleral tissue is primarily composed of collagen and elastic fibers, with a rich vascular network and lymphatic vessels, making it suitable for the deposition of various immune components—abdominal mass.

Episcleritis is clinically divided into two types:

1. Simple episcleritis: Also known as periodic fugax episcleritis (episcleritis periodica fugax).

Clinical symptoms include sudden diffuse congestion and edema in the affected area of the episclera and overlying bulbar conjunctiva, with a fiery red hue. The congestion may be localized or fan-shaped, mostly confined to one quadrant, and extensive involvement is rare. The superficial episcleral vessels are tortuous and dilated but remain radial, without the purplish hue of deep vascular congestion or localized nodules.

This condition is characterized by periodic recurrence, sudden onset, and short duration, resolving within a few days. About half of the patients experience mild pain, often described as a burning sensation or stabbing pain discomfort. Occasionally, pupillary constriction and temporary myopia may occur due to spasms of the iris sphincter and ciliary muscles. Eyelid neurovascular reactive edema may also appear during attacks. In severe cases, periodic migraine may accompany the condition, but vision is generally unaffected.

2. Nodular episcleritis: Nodular episcleritis is characterized by localized nodules. It often presents acutely with symptoms such as eye redness, pain, photophobia, tearing, and tenderness. Edema infiltration quickly appears on the episclera near the limbus, forming a pale red to fiery red localized nodule. The nodules vary in size, ranging from a few millimeters in diameter. The overlying bulbar conjunctiva can be freely moved and is tender to palpation.

The pale red lesions are caused by congestion of the vascular plexus in the bulbar conjunctiva, while the fiery red lesions are due to congestion of the superficial vascular plexus in the episclera. These can be differentiated using anterior segment fluorescein angiography.

The nodule is round or oval, usually solitary, and sometimes can reach the size of a pea. The nodule is located within the episcleral tissue and can be moved over the sclera, indicating no connection with the deep sclera. The scleral vascular plexus remains normal beneath the nodule.

The course of the disease is self-limiting within about 2 weeks. The nodule changes from fiery red to pink, and its shape flattens from round or oval before eventually being completely absorbed, leaving a trace with a bluish-gray hue on the surface. Inflammation may also recur in other locations after healing, with one nodule disappearing and another appearing, often recurring multiple times over several months. Due to repeated episodes in different areas, a circular pigmented ring around the corneal periphery may eventually form. Eye pain is more severe at night, though some cases may not exhibit significant pain. Vision is generally unaffected. Grade I keratitis is the only complication of episcleritis. If photophobia or tearing occurs, it suggests grade I keratitis, which is more commonly seen near the nodule at the corneal margin.

(II) Scleritis

Scleritis, also known as deep scleritis, is less common than episcleritis but has a more acute onset and is often accompanied by keratitis and uveitis, making it more severe with a poorer prognosis. Generally, episcleritis rarely involves the scleral tissue, whereas scleritis affects the sclera itself. Scleritis frequently occurs in the anterior sclera where blood vessels penetrate, while posterior scleritis near the equator is less common due to its invisibility and fewer blood vessels, making it easily overlooked. Scleritis can be classified into anterior scleritis and posterior scleritis based on location. Anterior scleritis is the more common form, predominantly affecting young adults or adults, with a higher incidence in women than men, and may occur in both eyes sequentially or simultaneously.

Scleritis is primarily caused by endogenous antigen-antibody immune complexes and is often associated with systemic collagen diseases, thus falling under the category of collagen disorders and related to autoimmunity. Benson (1988) attributed its immunogenicity to direct inflammation of collagen itself or the scleral matrix (glycosaminoglycans). Patients with primary necrotizing anterior scleritis may have altered tolerance to sclera-specific antigens and exhibit delayed-type hypersensitivity to soluble scleral antigens. The discovery of immune complexes in rheumatoid arthritis supports this theory. However, the cause of most scleritis cases remains difficult to identify.

1. Anterior Scleritis

(1) Diffuse Anterior Scleritis: This is the most benign form of scleritis and is rarely associated with severe systemic diseases.

Clinical symptoms include sudden diffuse congestion and swelling of the scleral tissue, making it difficult to assess the scleral condition. In severe cases, the conjunctiva may exhibit significant edema, necessitating the application of 1:1000 adrenaline to the conjunctival sac to confirm the presence of deep vascular congestion or nodules. Diffuse scleritis spreads more easily than the nodular type. The affected area may be limited to one quadrant or involve the entire anterior part of the eye, often accompanied by episcleritis.

(2) Nodular anterior scleritis: The clinical symptoms include severe eye pain that radiates to the surrounding orbit. About half of the patients experience tenderness in the eyeball. The inflammatory nodules are deep red and completely immobile, yet clearly demarcated from the overlying episcleral tissue. The surface vessels are elevated by the nodules. The nodules may be single or multiple. Infiltrative nodules can spread around the cornea and merge, forming annular scleritis. At this stage, the entire eyeball appears dark purple, interspersed with gray-white nodules, which leave behind a thin cyanotic scar after absorption. The course of the disease may be as short as a few weeks or months, or as long as several years. The infiltrates are gradually absorbed without ulceration, and the sclera becomes thin, appearing dark purple or porcelain white. Due to the inability to withstand intraocular pressure, partial scleral bulging or staphyloma may occur. The deep vascular plexus of the episclera becomes congested, presenting a purplish-red hue, and the vessels are immobile. The superficial and deep scleral vascular networks become twisted and irregular, with larger anastomotic branches between the deep vessels, resulting in a beaded appearance of vessel dilation and filling. If photophobia and tearing occur, concurrent keratitis and uveitis should be considered, which often severely impair vision.

(3) Necrotizing anterior scleritis: This condition is also known as inflammatory necrotizing scleritis. Although clinically rare, it is the most destructive form and often serves as a precursor to severe systemic collagen diseases. The disease progresses slowly and chronically. Approximately half of the patients experience complications and vision loss.

Clinical symptoms in the early stages manifest as localized inflammatory infiltration, with acute congestion, tortuous and occluded blood vessels in the affected area. A classic sign is the appearance of localized avascular patches. Beneath or near these avascular areas, scleral edema occurs, and superficial scleral vessels shift forward (easily detectable under red-free light). The progression of the lesion may remain confined to a small area or expand into large-scale necrosis, or spread bilaterally from the initial site, eventually affecting the entire anterior segment of the eye. After healing, the affected sclera continues to thin, revealing the underlying uveal pigment as a bluish-purple hue. Unless intraocular pressure remains persistently high (≥4.0 kPa or 30 mmHg), staphyloma rarely forms. If the necrotic area is small, newly formed collagen fibers may repair it. If the overlying conjunctiva is damaged, a depressed scar may develop. Ocular tenderness is present in about half of the cases.

Ye Lina et al. (1980) reported two cases of nodular necrotizing scleritis, both featuring progressive necrotic yellow nodules on the sclera, marked inflammation, and severe pain. The affected sclera appeared thin and bluish-purple, confirmed by pathological examination. After conventional treatments failed, both patients underwent lesion excision and lamellar corneal transplantation. One case improved, while the other recurred. Li Yingzhan (1980) documented a case of nodular necrotizing scleritis treated with immunosuppressants. The patient had bilateral involvement: the right eye was in the ulcerative stage, and the left eye in the nodular stage. A depressed ulcer (right eye) and a raised yellow nodule (left eye) were both located 4 mm from the limbus, with surrounding sclera showing purplish-red congestion and tenderness. Immunosuppressive therapy led to remission.

(4) Scleromalacia perforans: Also termed non-inflammatory necrotizing scleritis, this is a rare and distinctive form of scleritis. It progresses insidiously with almost no symptoms. About half of the cases are associated with rheumatoid arthritis or ankylosing polyarthritis. Ocular manifestations may precede joint disease. Most patients are women over 50 years old. The condition is typically bilateral but asymmetric in severity. Although progression is usually slow, some cases deteriorate rapidly, leading to blindness within weeks.

This disease rarely involves inflammation or pain. Characteristic lesions appear as yellow or gray patches on the sclera between the limbus and equator. In severe cases, the sclera gradually becomes necrotic and sloughs off, leaving complete scleral loss. The remaining sclera shows markedly reduced vasculature, appearing white and porcelain-like. About half of patients have multiple necrotic foci. The scleral defects caused by necrosis may be covered by thin connective tissue, likely derived from the conjunctiva. Staphyloma does not develop unless intraocular pressure rises. No cases exhibit ocular tenderness. The cornea remains unaffected.

The defective area lacks tissue regeneration, eventually leading to perforation and uveal prolapse.

Gong Chunhui (1985) reported a case of perforating scleromalacia. The patient had a 5–6-year history of arthritis, with fusiform soft tissue swelling in the left middle finger’s proximal interphalangeal joint but no redness or tenderness. X-rays showed no osteoporosis or joint space narrowing. The left eye exhibited redness followed by corneal opacity, with ulcerated sclera appearing bluish-purple and minimal irritation. Six months later, a 4×5 mm round ulcer developed 5 mm from the limbus above the medial rectus insertion, revealing blue sclera and dark purple choroidal tissue beneath the conjunctiva. The corneal edge showed ulceration from 12 to 5 o’clock, while the fundus was normal. Treatment with corticosteroids and lamellar corneal transplantation controlled the condition.

2. Posterior scleritis

Posterior scleritis refers to inflammation of the sclera occurring in the posterior part of the equator and around the optic nerve. Its severity is sufficient to cause destruction of the posterior ocular tissues. Due to the diversity of its manifestations and the rarity of its consideration during diagnosis, this condition—when not accompanied by anterior scleritis and without obvious external ocular signs—is one of the most easily misdiagnosed yet treatable ocular diseases. However, upon examining many enucleated eyes, it is not uncommon to find evidence of primary posterior scleritis or anterior scleritis extending posteriorly, indicating the clinically covert nature of posterior scleritis. This disease is also more common in women than in men and frequently occurs in middle-aged individuals.

(1) Clinical symptoms: The most common symptoms of posterior scleritis include varying degrees of pain, decreased vision, and eye redness. However, some individuals may exhibit no obvious symptoms or only one of these manifestations. Severe cases may present with eyelid edema, bulbar conjunctival edema, proptosis, or diplopia—or a combination of these. The symptoms can be difficult to distinguish from orbital cellulitis. The key differentiating feature is that the degree of edema in this condition is more pronounced than in cellulitis, whereas proptosis is more prominent in cellulitis compared to posterior scleritis. The intensity of pain varies, ranging from mild to excruciating, often correlating with the severity of anterior scleritis involvement. Patients may complain of pain in the eyeball itself or pain radiating to the brow, temple, or zygomaticotemporal region.

Decreased vision is a common symptom, attributed to associated optic nerve and retinal lesions. Some individuals report visual fatigue due to reduced myopia or increased hyperopia, which results from diffuse thickening of the posterior sclera shortening the axial length. Changing corrective lenses can alleviate these symptoms.

Clinically and pathologically, patients with posterior scleritis invariably exhibit anterior scleral involvement, manifested as dilated episcleral vessels in the fornix, patchy anterior scleritis, or nodular anterior scleritis. Ocular redness may be absent, but a history of pain and conjunctival injection or prior topical corticosteroid treatment may be noted.

Proptosis, drooping of the upper eyelid (blepharoptosis), and eyelid edema may occur in severe cases of periscleritis, where inflammation often extends to the extraocular muscles or orbit. Pain on eye movement or diplopia may result from extraocular muscle inflammation. These combined symptoms are referred to as periscleritis, sclerotenonitis, or acute anterior inflammatory pseudotumor.

Another, more superficial variant presents as prominent tenonitis with minimal scleral inflammation, termed "gelatinous tenonitis" by James. The bulbar conjunctiva appears semi-gelatinous, orange-red, and edematous, resembling fish flesh, with slight firmness and grade I pitting on pressure. The lesion may extend to the corneal limbus while the intraocular structures remain normal. In severe cases, the inflammation may invade the sclera, leading to gelatinous scleritis.

(2) Fundus lesions:

① Well-demarcated fundus mass: Localized scleral swelling can cause choroidal elevation, often surrounded by concentric choroidal folds or retinal striae. Such inflammatory nodules are typically accompanied by periorbital pain but may also be asymptomatic and detected incidentally during routine examination.

② Choroidal folds, retinal striae, and optic disc edema: These are the primary fundoscopic findings in scleritis. Patients often experience grade I pain or episcleral vessel congestion in the fornix. Scleral inflammation near the optic disc may occasionally cause optic disc edema.

③ Annular choroidal detachment: Some cases exhibit slightly spherical choroidal detachment adjacent to the scleritis lesion, though annular ciliochoroidal detachment is more common.

④ Exudative macular detachment: Posterior scleritis in young women can lead to posterior pole serous retinal detachment, confined to the posterior pole. Fluorescein angiography reveals multiple pinpoint leakage sites. Ultrasonography demonstrates thickening of posterior ocular layers and tenonitis edema.

Based on the above, Benson (1982) emphasized that unexplained angle-closure glaucoma, choroidal folds, optic disc edema, well-demarcated fundus masses, choroidal detachment, and serous retinal detachment should all raise suspicion for this condition.

bubble_chart Auxiliary Examination

Due to the fact that scleritis is often associated with immunogenic and allergenic factors, in addition to medical history and characteristic systemic and local signs serving as diagnostic bases, corresponding systemic examinations and laboratory tests are also necessary before treatment.

(1) Systemic Examination

X-ray examinations of the chest, spine, and sacroiliac joints.

(2) Laboratory Tests

Complete blood count, erythrocyte sedimentation rate, liver function tests, serum uric acid measurement, syphilis serological tests, subcutaneous nodule tuberculin intradermal test, etc. Immunological indicators: rheumatoid factor, peripheral blood T-lymphocyte subsets, peripheral blood immunoglobulins, immune complex measurement, antinuclear antibodies, complement C₃, etc.

(3) Anterior Segment Fluorescein Angiography for Scleritis

Watson (1984) first applied fluorescein angiography to the diagnosis of scleritis, proposing that in typical diffuse or nodular scleritis, fluorescein angiography shows enhanced fluorescence of the vascular bed and reduced transit time, i.e., congested vessels exhibit little or no blood flow. The filling pattern is abnormal due to the opening of anomalous anastomotic branches, forming vascular shunts. Fluorescein leaks early into the deep scleral tissue, and vascular filling is delayed. However, if the vessels remain patent during the disease, blood circulation will eventually recover. If the vessels are already blocked, they rarely reopen and are ultimately replaced by newly formed vessels. Particularly significant is that in diffuse, nodular, and necrotizing scleritis with marked inflammation, the occluded vessels are small veins, whereas in perforating scleromalacia, the blocked vessels are small arteries, especially those of the deep scleral plexus. Consequently, unlike other types of necrotizing scleritis, where inflammatory cells actively clear the damaged tissue, which is then replaced by sparse fibrous tissue, the result here is tissue infarction, followed by separation and gradual absorption (Table 2).

Table 2 Summary of Anterior Segment Fluorescein Angiography Findings in Scleritis

Diffuse		Slow flow rate, abnormal vascular morphology
Nodular		Slow flow rate, abnormal vascular morphology, localized deep leakage
Necrotizing	With inflammation	Slow flow rate, small vein occlusion, vascular occlusion disappearance, blood flow via new pathways
	Without inflammation	No blood flow, small artery occlusion, presence of large bypass vessels

Although there is still debate regarding the normal filling of these vessels and the non-filling of certain major vessels, observing the inflamed vascular layers and the vascular displacement accompanying scleral edema can help differentiate benign superficial scleritis from severe scleritis, aiding in early diagnosis and further research.

(4) Fundus Fluorescein Angiography

In cases with subretinal exudate, early fluorescein angiography shows mottled choroidal background fluorescence, followed by multiple pinpoint-sized hyperfluorescent areas, which gradually enlarge and brighten. In the advanced stage of angiography, fluorescein leaks into the subretinal fluid. Of course, these fluorescein angiography findings are not specific to posterior scleritis, but they aid in its diagnosis.

(5) Ultrasonography

Ultrasound scanning has become an indispensable method for diagnosing posterior scleritis and thickening in recent years. B-mode ultrasound scanning can reveal flattening of the posterior globe, thickening of the posterior layers, and retrobulbar edema. If the retrobulbar edema surrounds the optic nerve, a "T" sign may be observed. This sign indicates that the edema extending along the sclera forms a right angle with the normal circular shadow of the optic nerve.

(6) CT Scan Examination

CT shows thickening of the sclera, and the image can be enhanced with contrast injection. Retrobulbar edema may also be observed. However, similar manifestations can be seen in cases of idiopathic inflammatory orbital pseudotumor, acute periscleritis, and orbital cellulitis.

Ye Rongkun (1983) reported a case of unilateral proptosis caused by posterior scleritis: a 46-year-old female. The patient experienced decreased vision in the left eye for 5 months, proptosis for 1 month, restricted eye movement, diffuse congestion of the bulbar conjunctiva, and localized dark red congestion with nodules in the temporal equatorial region, accompanied by significant tenderness. The fundus examination revealed optic disc congestion and edema, elevated by 2.0D, and grade I macular edema. The condition improved after systemic and local antibiotic and corticosteroid treatment. Liu Bingzhi et al. (1982) reported a case of posterior scleritis with slight forward protrusion of the eyeball (>2 mm compared to the healthy side), congestion and edema of the bulbar conjunctiva, and increased pain during eye movement. The optic disc margins were blurred, red, and anteriorly convex, with central venous filling and tortuosity, grade I retinal edema, and radial folds in the macular area, with absence of the foveal light reflex. Treatment with sufficient doses of corticosteroids, vasodilators, and neurotrophic agents resulted in visual acuity improvement from 0.3 to 0.8. No recurrence was observed during the 2-year follow-up.

bubble_chart Treatment Measures

The treatment principles for scleritis should first clearly identify the disease cause and proceed with cause-specific treatment while preventing recurrence. Enhancing nutrition to improve overall physical condition is also necessary.

(1) Episcleritis

Whether simple or nodular, episcleritis is a benign, recurrent, mild condition with a self-limiting course of 1–2 weeks or longer, and may not require treatment. However, to expedite recovery, topical corticosteroid eye drops can be applied to leverage their nonspecific anti-inflammatory effects, alleviating symptoms and scleritis damage. Alternatively, non-corticosteroid anti-inflammatory agents such as indomethacin or phenylbutazone may also yield therapeutic effects. Other symptomatic topical eye drops should be routinely used for all types of scleritis. For instance, when scleritis is complicated by iridocyclitis, atropine should be promptly administered to fully dilate the pupil.

Painful episcleritis is an exception, as its pathogenesis involves the rupture of phagocyte vacuoles. Therefore, it should be treated with uricosuria. If necessary, topical corticosteroids may be administered.

(2) Scleritis

For diffuse and nodular scleritis, the vascular plexus in the affected area remains open, but the disease course is prolonged. In addition to topical medication, oral corticosteroid preparations should be added. If complicated by uveitis, mydriatics should be promptly administered.

(3) Necrotizing Scleritis

The condition is severe, with most of the vascular plexus occluded. For cases such as syphilis, subcutaneous nodules, or leprosy, targeted disease-specific therapies should be administered alongside short-course systemic non-corticosteroid anti-inflammatory treatments, such as oral oxyphenbutazone or indomethacin. If ineffective within a week and avascular areas appear in the sclera, sufficient doses of corticosteroid preparations, such as oral prednisone or dexamethasone, should be administered to suppress the necrotic process. Once the condition is controlled, the dosage should be tapered to a maintenance level until the disease subsides.

Subconjunctival injections are contraindicated in patients with deep scleritis to prevent scleral perforation. However, systemic or retrobulbar corticosteroid injections often alleviate scleritis, periscleritis, scleral tenonitis, and acute inflammatory orbital pseudotumors, effectively relieving severe pain without complications.

In severe cases, stronger immunosuppressants such as cyclophosphamide may sometimes be required, either as a corticosteroid-sparing agent or in combination with anti-prostaglandin non-steroidal anti-inflammatory agents to reduce systemic steroid doses to acceptable levels. However, it is generally believed that true perforating scleral softening caused by partial anterior segment microvascular obstruction should be treated before necrosis occurs. For patients with systemic immune diseases such as Wegener's granulomatosis, the goal is to suppress lymphocyte production, and the combined use of immunosuppressants and corticosteroids yields optimal results. For other systemic vasculitides or cases involving only circulating immune complexes, corticosteroids alone may suffice.

Surgical treatment is only applicable when the inflammatory source is confirmed to be autoimmune. Resecting necrotic tissue can eliminate antigen sources, and implanting allogeneic sclera is also an effective treatment.

In recent years, reports have emerged on the use of cyclosporine A, a novel and potent immunosuppressant that selectively acts on helper T lymphocytes to exert immunosuppressive effects without bone marrow toxicity. Initially used in ophthalmology to treat corneal melting syndrome, it has since demonstrated definitive efficacy in treating necrotizing scleritis, Mooren's ulcer, and corneal transplant rejection. It has also been formulated into topical eye drops for clinical use.

bubble_chart Complications

The ocular complications of scleral inflammation are numerous and mostly occur in the advanced stage of inflammation. The complications depend on the severity and nature of the inflammation. Superficial scleritis accounts for about 15%, while scleritis exceeds 57%, particularly prevalent in severe necrotizing scleritis. When the inflammation spreads and secondary endophthalmitis occurs, complications include various types of keratitis or corneal lesions, leukoma, uveitis, glaucoma, and scleral thinning (defects), among others.

(1) Sclerosing Keratitis

Sclerosing keratitis, also known as progressive scleroperikeratitis, predominantly affects older women, often bilaterally, with recurrent episodes leading to involvement of the entire cornea and complications such as iridocyclitis or glaucoma, resulting in severe consequences.

The pathological features include edema and infiltrative changes in the scleral tissue around the corneal limbus, accompanied by dense neovascularization that invades the deep corneal layers, causing corneal opacity. This opacity typically occurs at the limbus but can also appear on the central corneal surface or within the stromal layers, unrelated to the scleral lesion. Initially, the corneal opacity appears grayish-white or grayish-yellow, later turning white, often forming a tongue-shaped or triangular pattern with the apex pointing toward the corneal center. Linear opacities may persist within the corneal stromal lamellae, resembling porcelain-like streaks, which are permanent once they appear. In severe cases, the opacity may progress into a ring shape, leaving only a central transparent area that may eventually disappear, resulting in complete opacity—termed "sclerosing keratitis." Rarely, the condition may develop into a sclerocorneal marginal ulcer.

The term "sclerosing keratitis" refers to the porcelain-like appearance of the affected corneal tissue, resembling sclera, rather than indicating sclerotic pathological changes.

(2) Keratolysis

This condition is characterized by the separation and dissolution of the corneal epithelial layer in cases of severe necrotizing scleritis or perforating scleromalacia, sometimes involving areas several millimeters wide. In severe cases, Descemet's membrane may bulge and become extremely thin, easily ruptured. Similar tissue dissolution may occur in the affected sclera. Corticosteroid therapy can halt this process, suggesting that inhibiting collagen activity also suppresses disease progression.

(3) Scleral Defect

This is seen only in the most severe cases of scleral necrosis. If necrotizing scleritis is accompanied by inflammation, the episcleral vessels disappear, and the underlying scleral tissue becomes non-perfused, eventually necrotic. In perforating scleromalacia, tissue necrosis may occur without warning. Once necrosis occurs, the sclera becomes thin and transparent, sometimes perforating.

(4) Uveitis

According to many studies, about 35% of scleritis patients develop uveitis and retinitis. Both anterior and posterior uveitis cases should be closely monitored for coexisting scleritis, and vice versa. Posterior scleritis with uveitis presents with severe symptoms, often accompanied by retinal detachment. Some reports also note inflammatory cells in the anterior chamber and vitreous. Histologically, Wilhelmus observed inflammation in the choriocapillaris, as well as cuff-like infiltrates around the central retinal artery, its branches, and posterior ciliary vessels.

(5) Glaucoma

Elevated intraocular pressure can occur at any stage of scleritis. The reasons include: ①Ciliary body and choroidal exudation causing forward displacement of the iris-lens diaphragm, leading to angle closure and acute angle-closure glaucoma; ②Inflammatory cell infiltration in the anterior chamber obstructing the trabecular meshwork and angle; ③Perivascular lymphocytic cuffing in the superficial scleral vessels, resulting in elevated scleral venous pressure; ④Perivascular lymphocytic cuffing around Schlemm's canal, affecting aqueous outflow; ⑤Long-term local, periocular, or systemic use of corticosteroids, inducing corticosteroid-induced glaucoma.