Scleral Inflammation: Causes and Treatment

Inflammation of the Sclera and Sub-Scleral Layers: An Overview

Inflammation of the sclera, commonly referred to as scleritis, and its associated sub-scleral structures, constitutes a significant area of study within ophthalmology. The sclera is the dense, white outer layer of the eyeball that provides structural support and protection for the inner ocular tissues. It plays a crucial role in maintaining the shape of the eye and serves as an attachment site for the extraocular muscles that facilitate eye movement. Understanding the mechanisms, causes, symptoms, and treatment options for scleral and sub-scleral inflammation is essential for the effective management of patients presenting with these conditions.

Anatomy and Function of the Sclera

The sclera is composed primarily of collagen and elastin fibers, forming a robust structure that protects the eye’s inner components, including the choroid, retina, and vitreous body. The sclera is divided into three main regions:

Episclera: This thin layer lies just beneath the conjunctiva and is composed of loose connective tissue. The episclera contains blood vessels and nerves, which play a critical role in the nutrition and innervation of the sclera.
Scleral Layer: The main body of the sclera, it provides structural integrity to the eyeball. The scleral layer is avascular, meaning it lacks blood vessels, which is important for maintaining clarity in the adjacent structures of the eye.
Sub-Scleral Layer: This layer consists of connective tissue that supports the sclera and facilitates its interaction with the underlying uveal tract, which includes the choroid, ciliary body, and iris.

Causes of Scleritis

Scleritis is categorized into several types based on its underlying causes:

Non-Infectious Scleritis: This is the most common form and is often associated with systemic autoimmune conditions, such as rheumatoid arthritis, lupus, and vasculitis. In these cases, the inflammation of the sclera can be a manifestation of a broader systemic disease.
Infectious Scleritis: Although less common, infectious scleritis can occur due to bacterial, viral, or fungal infections. Conditions such as herpes zoster ophthalmicus or bacterial endophthalmitis can lead to inflammation of the sclera.
Traumatic Scleritis: Injury to the eye, including surgical trauma or penetrating injuries, can result in localized inflammation of the scleral tissue.
Idiopathic Scleritis: In some cases, the cause of scleritis remains unknown, and it is classified as idiopathic.

Symptoms of Scleritis

The clinical presentation of scleritis can vary depending on the severity and type of inflammation. Common symptoms include:

Ocular Pain: Often described as a deep, aching pain that can radiate to the forehead or jaw. Pain may worsen with eye movement and can be severe, leading to functional impairment.
Redness: The affected eye may appear reddened due to dilation of the conjunctival blood vessels. In diffuse scleritis, there is widespread redness, while nodular scleritis presents with localized areas of inflammation.
Photophobia: Increased sensitivity to light can occur, making it uncomfortable for patients to be in bright environments.
Vision Changes: Blurred vision or visual disturbances may result from associated conditions affecting the retina or cornea.
Tearing: Increased tear production can occur in response to ocular irritation.

Diagnosis of Scleritis

The diagnosis of scleritis involves a comprehensive clinical evaluation, including:

Patient History: A thorough medical history is essential to identify any underlying systemic conditions, prior ocular surgeries, or recent infections.
Ocular Examination: An ophthalmologist will conduct a detailed examination using slit-lamp biomicroscopy to assess the extent of scleral inflammation. Signs such as scleral thickening, nodules, or associated conjunctival involvement will be noted.
Imaging Studies: In some cases, advanced imaging techniques, such as optical coherence tomography (OCT) or ultrasound, may be employed to evaluate the extent of inflammation and assess for complications.
Laboratory Tests: Blood tests may be performed to screen for systemic autoimmune diseases or infections.

Treatment of Scleritis

The management of scleritis primarily depends on its underlying cause and severity. Treatment options include:

Medications:
- Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): Oral NSAIDs may be prescribed for mild cases to reduce inflammation and alleviate pain.
- Corticosteroids: Systemic corticosteroids, such as prednisone, are often the mainstay for treating moderate to severe scleritis, especially when associated with systemic autoimmune diseases. Topical corticosteroids may also be used in some cases.
- Immunosuppressive Agents: In cases where scleritis is linked to systemic autoimmune conditions that are refractory to corticosteroids, immunosuppressive medications such as methotrexate or azathioprine may be indicated.
Surgical Intervention:
- Surgical intervention may be necessary in cases of complicated scleritis, such as those involving scleral perforation or the presence of associated ocular diseases that require surgical correction.
Management of Underlying Conditions:
- Effective management of any underlying systemic disease is crucial to preventing recurrent episodes of scleritis.

Complications of Scleritis

Scleritis can lead to several complications if left untreated or inadequately managed. These complications may include:

Scleral Thinning: Persistent inflammation can lead to thinning of the sclera, increasing the risk of perforation.
Corneal Involvement: The inflammation can extend to the adjacent cornea, resulting in keratitis or corneal ulcers.
Uveitis: Inflammation may also involve the uveal tract, leading to uveitis, which can further compromise vision.
Vision Loss: Severe cases of scleritis, especially those associated with complications, may result in permanent vision loss.

Prognosis

The prognosis for individuals with scleritis largely depends on the underlying cause, severity, and promptness of treatment. With appropriate management, many patients experience significant improvement in symptoms and ocular health. However, some individuals may experience recurrent episodes or chronic inflammation, necessitating long-term monitoring and treatment.

Conclusion

Inflammation of the sclera and sub-scleral structures is a complex condition with various etiologies, symptoms, and potential complications. Understanding the underlying mechanisms and effective management strategies is essential for ophthalmologists and healthcare providers to optimize patient outcomes. Early diagnosis and appropriate treatment can significantly reduce the risk of complications and preserve visual function in affected individuals. Continued research into the pathophysiology of scleritis and its associated systemic conditions will enhance our understanding and management of this important area in ophthalmic practice.