In 1976, Watson and Hayreh proposed a clinical classification of scleritis (Table 5.1) based upon the anatomic location of the inflammation and the observed alterations in the associated vascular structures . This categorization of dis ease entities does not infer aetiology, but provides valuable information regarding severity of inflammation, prognosis, management options, and association with systemic diseases and with ocular complications. Few patients (<10 %) progress to a different form of scleritis from their initial presentation .
Scleritis is defined as anterior or posterior based upon the location of inflammation, relative to the equator of the globe. The majority of scleritis is anterior and can be categorized as non-necrotizing or necrotizing. Diffuse (4045%) and nodular (23-44%) scleritis are non-necrotizing and represent the most common forms of anterior scleritis (Table 5.2). The necrotizing types of anterior scleritis are less common (14-26%), but represent a more severe disease entity [34, 45]. Necrotizing scleritis is classified as either with inflammation or without inflammation, with the latter being synonymous with scleromalacia perforans.
Posterior scleritis represents a more heterogeneous spectrum of inflammation that is less amenable to classification. The prevalence of 2-12% for posterior scleritis may be underrep-resentative, due to its low incidence and under-recognition on clinical examination [3, 34, 45]. Singh and Foster previously subdivided posterior scleritis as either chronic or acute . Ultrasonographic classification categorizes posterior scleritis as diffuse or nodular, based upon
increased eye wall thickness or the finding of scleral nodules, respectively .
Although scleritis is most often idiopathic or associated with a systemic disease, scleritis can also be postsurgical or related to an infectious process (Table 5.4). In previous studies, 25-57% of scleritis cases were associated with a known systemic condition [34, 42, 45]. In the Watson and Hayreh series, connective tissue disorders were present in 15% of the patients, of which rheumatoid arthritis constituted 10% . In another series with a higher proportion of necrotizing scleritis cases, half (48%) of the patients had an associated systemic connective tissue or vasculitic disease . Necrotizing scleritis has the highest association (45-95%) with systemic illness and represents the most frequent type of scleritis that is the first manifestation of a systemic condition [34, 45]. Approximately two-thirds of patients with scle-romalacia perforans have an associated systemic condition , most commonly longstanding rheumatoid arthritis (47%) . Diffuse scleritis appears to be the most benign form with the lowest prevalence of associated systemic illness. Nodular scleritis and posterior scleritis have an intermediate prevalence with associated systemic conditions. Systemic conditions associated with scleritis include Wegener's granulomatosis, relapsing polychrondritis, systemic lupus erythematosus, inflammatory bowel disease, Reiter's syndrome, psoriatic arthritis, polyarteritis nodosa, ankylosing spondylitis, Behçet's disease, giant cell arteritis, and Cogan's syndrome [12,23,34,45]. Vasculitis is a proposed common factor in the pathogene-sis of both scleritis and the systemic autoimmune disorders.
Scleritis may occur following ocular trauma, including surgery (Fig. 5.1). The aetiology is unclear, but is hypothesized to be driven by an aberrant, immune-mediated response with a resultant vasculitis. These patients may be predisposed to autoimmune disorders, where trauma initiates the inflammatory cascade that causes scleritis [19,27,32,38]. Surgically induced necrotizing scleritis (SINS) can occur after any type of ocular surgery with scleral manipulation, including cataract surgery, strabismus surgery, filtering blebs, pterygium surgery, and operations for retinal detachments [19,27,32,38]. The onset of progressive scleral inflammation with scleral destruction most frequently occurs within 6 months, but can occur as early as 1 day or as distant as years after the surgery [19,27,32,38]. Inflammation is typically localized to the site or adjacent to the site of surgery, but may progress to involve the entire sclera [19, 32]. Necrotizing scleritis (94%) and posterior scleritis occur more often, compared with other forms of scleritis . The presence of necrotizing scleritis following an uncomplicated ocular surgery may represent the first manifestation of an unrecognized systemic illness. The prevalence of an underlying systemic disease in patients with SINS is approximately 62-90% [19, 27, 32,
Additionally, scleritis may develop due to a primary infectious aetiology (Fig. 5.2) or secondarily as an immune response to a pathogen.
Table 5.3. Systemic diseases associated with scleritis
Inflammatory bowel disease:
ulcerative colitis and Crohn's disease
Systemic lupus erythematosis
Giant cell arteritis
Lymphoma (Hodgkin's) Pyoderma gangrenosum Cogan's syndrome Necrobiotic xanthogranuloma Poststreptococcal vasculitis
Various bacterial, viral, fungal, and parasitic infections have been implicated in scleritis [10,17, 21]. Pseudomonas scleritis is the most common cause of infectious scleritis and requires early recognition due to its potential for severe tissue destruction . Infectious scleritis usually results from a traumatic mechanism or from extension of an infection involving other ocular tissues (Table 5.4).
• The clinical classification of scleritis based upon anatomic location and alterations in vascular structures (Table 5.1) provides prognostic information regarding severity of inflammation, prognosis, therapy, and association with ocular and systemic morbidity
• Scleritis is relatively rare and the majority of cases (94-98%) are anterior
Table 5.4. Infectious scleritis
Bacterial Pseudomonas Proteus mirabilis Staphylococcus epidermidis Streptococcus pneumoniae Viral
Herpes zoster Herpes simplex Mumps Granulomatous Mycobacterium tuberculosis Mycobacterium chelonae Mycobacterium leprae Syphilis Fungal Aspergillus
Pseudallescheria boydii Sporotrichosis Parasitic Acanthamoeba Toxocariasis Toxoplasmosis Onchocerciasis
• Twenty-five to 57 % of scleritis cases are associated with a systemic disorder, most commonly rheumatoid arthritis (Table 5.3)
• Although most scleritis cases are considered idiopathic or associated with a systemic condition, scleritis can be postsurgi-cal or related to an infectious pathogen (Table 5.4)
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