The sclera is a relatively avascular structure, composed principally, of collagen and elastic tissue (1)
Scleritis is an inflammatory condition in which the outer shell of the eye, the sclera, becomes oedematous and tender
- often acutely painful and the ocular morbidity can be significant due to complications including decreased vision, uveitis, glaucoma, and rarely, globe perforation
- estimated a prevalence of 6 cases per 10,000 people (2)
Often, it may be affected by autoimmune, infectious, degenerative, metabolic, and hypersensitivity disorders which affect the joints (1)
- 21% are associated with rheumatoid arthritis and other collagen diseases;
- 12% with ankylosing spondylitis; and 15% with herpes zoster, TB, syphilis, gout and Reiter's disease
Scleritis is associated with underlying systemic disease in approximately 50% of patients depending on the clinic setting and referral patterns (2,3)
- classified in numerous ways: anterior or posterior, nodular or diffuse, necrotizing or non-necrotizing, and infectious or non-infectious
- systemic disease associations of scleritis include rheumatoid arthritis (RA), relapsing polychondritis, granulomatosis with polyangiitis (GPA; formerly Wegener's granulomatosis), systemic lupus erythematosus (SLE), inflammatory bowel disease (IBD), sarcoidosis, TB, Sweet syndrome, the seronegative spondyloarthopathies, and multiple forms of systemic vasculitis including Behcet's disease and Takayasu's arteritis
- in about 50% of cases, no underlying systemic disorder is identified
Anterior, non-necrotizing, non-infectious scleritis is the most common form, and it is further characterized as diffuse or nodular
- dilation of the superficial and deep episcleral vasculature resulting in a violaceous or bluish-red hue in the section of the sclera involved
- nodular form is present if there is a visible elevation with engorged scleral vessels
- scleritis can be unilateral or bilateral
- usually exquisitely painful
- instillation of phenylephrine will not blanch the scleral vessels - can be a useful test to differentiate between episcleritis and scleritis
- vision is minimally affected in acute disease unless there is concurrent involvement of the cornea or uveal tract
Necrotizing anterior scleritis without inflammation, also referred to as scleromalacia perforans - generally painless and rarely leads to globe perforation
- the underlying uveal tissue may be visible through the thinned sclera giving it a blue-gray to brown appearance
- associated with rheumatoid arthritis
- typically bilateral
- surgically induced necrotizing scleritis is a rare condition
- presumably autoimmune and follows multiple surgical traumas to the eye
Posterior scleritis is inflammation of the sclera that is behind the orbital septum and is not visible to the casual observer
- process is usually unilateral and can be associated with significant pain, especially on eye movement but may also be painless
- underlying systemic association is found in about 30% f patients.
An infectious cause is responsible for approximately 5-10% of cases of anterior scleritis.
- outcome of infectious scleritis is generally worse than with non-infectious scleritis, with only 40% of eyes retaining vision better than 20/200 after treatment, and up to 25% of eyes requiring evisceration.
Reference:
- The Practitioner 1997; 241: 192
- Smith JR, Mackensen F, Rosenbaum JT. Therapy insight: scleritis and its relationship to systemic autoimmune disease. Nat Clin Pract Rheumatol. 2007;3:219-26.
- Raiji VR, Palestine AG, Parver DL. Scleritis and systemic disease association in a community-based referral practice.Am J Ophthalmol. 2009;148:946-50
- Sainz de la Maza M, Molina N, Gonzalez-Gonzalez LA, Doctor PP, Tauber J, Foster CS. Clinical characteristics of a large cohort of patients with scleritis and episcleritis. Ophthalmology. 2012;119:43-50
- Hodson KL, Galor A, Karp CL, et al. Epidemiology and Visual Outcomes in Patients With Infectious Scleritis. Cornea. 2012