The sclera is a tissue with few cells and blood vessels, mostly composed of collagen. Its surface is covered by the spherical conjunctiva and spherical fascia, which are not in direct contact with the external environment.
I. Treatment measures
The principles of treatment for sclerochoroiditis are to firstly identify the cause, treat the cause, and prevent recurrence. Enhanced nutrition to improve the general condition is also necessary.
1. Superficial sclerositis
Superficial sclerositis, whether simple or nodular, is a benign recurrent mild disease with a self-limiting course of 1-2 weeks or more, and can be left untreated. However, topical corticosteroid drops can be applied to the eyes to relieve the symptoms and scleral damage in order to cure it as soon as possible. Or the application of non-corticosteroid anti-inflammatory agents, such as anti-inflammatory pain, POTUS, etc. can also receive therapeutic effect. Other topical symptomatic eye drops should be used routinely for all types of scleral inflammation, such as when scleral inflammation is complicated by iridocyclitis, atropine drops should be used promptly to adequately dilate the pupil.
The exception is gout, whose pathogenesis is due to the rupture of phagocytic vacuoles and should therefore be treated with uricosuria (uric acid-promoting urine). If necessary, local corticosteroid treatment should be given.
2. Sclerositis
In diffuse and nodular sclerositis, the vascular plexus of the affected area is open, but the disease is prolonged, so in addition to topical administration, corticosteroid preparations should be added. If complicated by uveitis, pupil dilators should be given promptly.
3. Necrotizing sclerochoroiditis
The disease is severe and most of the vascular plexus is occluded. Such as syphilis, tuberculosis, leprosy, etc., should be given to the cause of the special treatment and with a short course of systemic non-corticosteroid anti-inflammatory agent treatment. If the treatment is not effective within 1 week, the sclera should be treated with adequate doses of corticosteroids, such as prednisone or dexamethasone, to inhibit the necrotic process of the lesion. Once the lesion is controlled, the dose is reduced to a maintenance dose until the disease subsides.
Subconjunctival injections should be considered contraindicated in patients with deep scleral infection to prevent scleral perforation. However, systemic or retrobulbar corticosteroid injections usually provide relief from sclerositis, perisclerositis, scleral bulbar fasciitis, and acute inflammatory orbital pseudotumors, and are effective in reducing severe pain without complications.
In severe cases it is sometimes necessary to use stronger immunosuppressive agents such as cyclophosphamide, which is sometimes used as a decongestant of corticosteroids, or in the addition of antiprostaglandin non-steroidal anti-inflammatory agents to achieve a reduction in systemic steroid doses to acceptable levels. However, it is generally accepted that some patients with true perforated scleral softening caused by small anterior segment artery obstruction should be treated long before necrosis develops.
In patients with diseases involving the systemic immune system, such as Wegener’s granulomatosis, treatment is aimed at the need to suppress lymphocyte production, and immunosuppressive agents in combination with corticosteroids give the best results, whereas in other patients with systemic vasculitis or circulating immune complex disease only, corticosteroid therapy is required.
Surgical treatment is only indicated when it is certain that the source of inflammation is an autoimmune disease, and the removal of necrotic tissue, which removes the source of antigen, as well as the implantation of allogeneic sclera, are also effective treatments.
Cyclosporine A, a new potent immunosuppressive agent that selectively acts on helper T lymphocytes to exert its immunosuppressive effects without myelotoxicity, was first used in ophthalmology to treat keratolytic syndrome. In recent years, it has achieved positive efficacy in necrotizing sclerositis, nibbling corneal ulcer and corneal transplant rejection. And it has been able to be formulated into topical eye drops for clinical application.
Etiology
The etiology of sclerositis is unknown, sometimes not only the cause cannot be found, but even the primary site of inflammation is in the sclera, upper sclera, bulbar fascia or other parts of the orbit is not clear, for example, posterior sclerositis is difficult to distinguish from acute inflammatory orbital pseudotumor.
1. Exogenous infection
Exogenous infections are rare and can be caused directly by bacteria, viruses, fungi, etc. through foci of conjunctival infection, trauma, surgical wounds, etc.
2, endogenous infection
(1) septic metastatic (septic bacteria).
(2) Non-suppurative granulomatous (tuberculosis, syphilis, leprosy).
3.Ocular manifestations of connective tissue diseases
Connective tissue disease (collagen disease) is related to autoimmune diseases, such as rheumatoid arthritis, necrotizing nodular lupus erythematosus, periarteritis nodosa, sarcoidosis (nodular disease), Wegener’s granulomatosis, recurrent polychondritis and other complications of sclerositis, caused by fibrin-like necrotizing changes in the sclera, which are similar in nature to connective tissue disease. The complication rate is about 50% or more in billet scleritis and even higher in perforated scleral softening.
Other complications of sclerositis have been reported in patients with ankylosing spondylitis, Bencet’s disease, dermatomyositis, IgA nephropathy, temporal arteritis, and porphyria. Studies on the mechanism of induced sclerositis after animal experiments pointed out that this type of granulomatous change may indicate that the lesion is a type III hypersensitivity reaction caused by the deposition of locally produced antigens (in IV delayed hypersensitivity reactions) or circulating immune complexes in the eye that induce an immune response.
In type III hypersensitivity reactions, the vascular response is the result of antigen-antibody binding action on the vessel wall. These complexes are deposited on the walls of small veins and activate complement, which causes an acute inflammatory response. Therefore, collagen disease is an autoimmune disease with dysregulated immune mechanisms related to individual genes, or one of its manifestations.
III. Pathological changes
Biopsy of scleral lesions is more dangerous and is often done. Pathologic changes can only be studied at the time of removal of the eye or on diseased tissue excised during surgery. The infiltrates, hypertrophy and nodules present in the presence of sclerochoroiditis are chronic granulomatous lesions with fibrin-like brakes and collagen destruction. Septic inflammation is less common except from external infections or metastases from adjacent septic foci. Restricted inflammation can occur at sites of vascular access.
Granulomatous inflammation can be focal or diffuse, but is essentially the same in that the invaded sclera exhibits a chronic inflammatory infiltrate of cells that include polymorphonuclear leukocytes, lymphocytes, and macrophages, forming nodular and diffuse hypertrophic lesions. The granulomas are surrounded by multinucleated epithelioid giant cells and old and new blood vessels, some of which have thrombosis and exhibit features of vasculitis. These changes sometimes extend peripherally, well beyond the site of the granuloma, first involving the scleral mucopolysaccharide away from the lesion and showing diminished colloidal iron staining.
The fibers at the receptive granuloma are pushed apart by mucus edema, and the mucopolysaccharides only form patchy staining. Collagen fibrils are also seen to absorb stain under electron microscopy. The cellular alteration here is a marked increase in the number and activity of collagen fibroblasts, while within the granuloma there is a significant increase in the cellular component, with the area being infiltrated by plasma cells, lymphocytes and macrophages outside, some of which aggregate into giant cells. The scleral collagen fibrils lost their double refraction in polarized light. In the necrotic area, groups of infiltrating cells, mainly plasma cells, are seen, with cell brakes and proliferation of collagen fibers.
Clusters of neovascularization originating from the upper sclera or choroid were present in this area. Both old and new vessels have mesangial necrosis, mucopolysaccharide deposition, and thrombosis is seen. Many vessels have fibrin deposits in and around them.
In superficial lesions, the subconjunctival and superficial sclera are invaded, and scleral edema may show interlaminar separation with interstitial lymphocytic infiltration, along with superficial scleral vascular congestion and lymphatic vessel dilation. In mild cases, the healing process is usually uneventful. Inflammation of the anterior sclera can also affect the cornea, and in contrast, anterior chamber pus-forming keratitis can also affect the sclera and produce superficial scleritis.
In necrotizing sclerositis, fibrin-like necrosis occurs in the central area of the lesion, surrounded by large mononuclear cells like a fence, and in severe cases, lamellar avascular areas (arterial occlusion) may occur in the center of the inflammatory cell infiltration, with painful tissue degeneration, followed by fatty degeneration or vitreous degeneration, calcification, etc. The necrotic part gradually absorbs fibrosis and forms a scar, and this local sclera becomes thin and dilated, or the tissue becomes hypertrophic to form the so-called “hypertrophic scleritis”.