Scleromalacia is a severe eye condition that affects the sclera, the tough, white outer layer of the eyeball. This progressive disorder can lead to significant thinning and, in some cases, perforation of the sclera. If not addressed promptly, scleromalacia can result in severe visual impairment or even blindness.
Understanding Scleromalacia
The sclera forms the protective outer wall of the eye, providing structural integrity and protecting the delicate inner components. In scleromalacia, this normally robust tissue undergoes a degenerative process, leading to its progressive weakening and thinning. The term “sclera” refers to the white part of the eye, and “malacia” indicates a softening or degeneration of tissue.
Scleromalacia is a form of necrotizing scleritis without significant inflammation, meaning tissue damage occurs without the typical redness and swelling of other inflammatory eye conditions. The breakdown involves the activation of scleral fibrocytes, cells responsible for maintaining the scleral matrix, leading to the resorption of the surrounding pericellular matrix. This process, along with potential infiltration of inflammatory cells and prolonged local vaso-occlusion, contributes to the destruction of scleral tissue.
The progressive nature of scleromalacia can result in full-thickness loss of the conjunctiva, the clear membrane covering the sclera, and an inability of the conjunctival epithelium to resurface the exposed area. This exposes the underlying dark choroid, a vascular layer of the eye. The insidious onset and slow progression mean that specific symptoms may not be observed until this discoloration becomes apparent.
Associated Conditions and Causes
Scleromalacia is linked to systemic autoimmune diseases, where the body’s immune system mistakenly attacks its own tissues. Rheumatoid arthritis is the most common underlying cause, particularly in elderly women with long-standing disease. The immune response in these conditions can lead to chronic inflammation that weakens and thins the sclera.
Other autoimmune conditions associated with scleromalacia include:
Systemic lupus erythematosus
Granulomatosis with polyangiitis (formerly Wegener’s granulomatosis)
Polyarteritis nodosa
Relapsing polychondritis
Behçet disease
Limited scleroderma
Crohn’s disease
Graft-versus-host disease
While rare, some cases have also been reported in porphyria and herpes-zoster infection.
The pathogenesis involves a type III hypersensitivity reaction, where immune complexes—combinations of antigens and antibodies—accumulate and contribute to the autoimmune damage of the episcleral and scleral vessels. This immune-mediated attack on ocular tissue explains why individuals with these systemic conditions are at a higher risk of developing scleromalacia.
Identifying Symptoms and Diagnosis
The initial symptoms of scleromalacia can be subtle, non-specific, or even asymptomatic, sometimes starting with mild irritation. As the condition progresses, a characteristic sign is the appearance of necrotic scleral plaques near the limbus, the border between the cornea and sclera, without significant vascular congestion. These necrotic areas can coalesce and enlarge, leading to noticeable scleral thinning.
The thinning of the sclera can become so pronounced that the underlying pigmented uveal tissue, particularly the choroid, becomes visible through the translucent sclera, appearing as a dark or bluish area. In advanced cases, a calcified plaque may be expelled. Diagnosis involves a comprehensive eye examination performed by an ophthalmologist, who can observe these changes.
Imaging techniques like ultrasound and optical coherence tomography (OCT) can assess the extent of scleral thinning and rule out other conditions. A thorough review of the patient’s medical history for pre-existing systemic autoimmune diseases is an important part of the diagnostic process. Early detection is important to initiate management and potentially prevent severe complications.
Managing Scleromalacia
Managing scleromalacia involves addressing the underlying systemic autoimmune disease and controlling inflammation to prevent further scleral damage. Medical management relies on immunosuppressive therapy to modulate the body’s immune response. This can include systemic glucocorticoids, such as corticosteroids, to reduce inflammation.
Other immunosuppressants commonly used include:
Methotrexate
Cyclophosphamide
Mycophenolate
Azathioprine
Rituximab
Tocilizumab
Tofacitinib
Biologic agents, particularly TNF-alpha inhibitors, are also part of the therapeutic arsenal for managing the systemic conditions that drive scleromalacia. Topical treatments like glucocorticoids, tacrolimus, and cyclosporine may also be employed.
Pain management is addressed as needed, although scleromalacia is typically non-painful in its early stages. For severe cases, particularly when scleral perforation is imminent or has already occurred, surgical interventions become necessary. Scleral grafting, which involves transplanting scleral tissue, is a common surgical approach to repair perforations and reinforce weakened areas, preventing further thinning and potential rupture of the globe. Ongoing monitoring of the eye and the underlying systemic condition is necessary to manage the disease and prevent complications such as significant vision loss or secondary infections like endophthalmitis.