Monday, October 31, 2011

Salzmann’s Nodular Degeneration

Signs and Symptoms
Most cases of Salzmann’s nodular degeneration present asymptomatically. Discomfort does not usually occur until later stages, at which time recurrent corneal erosion (RCE) may ensue. Patients manifesting RCE typically report photophobia, blepharospasm, tearing, and decreased acuity. In between bouts of RCE, non-specific "dry eye" complaints such as burning or grittiness are typical.

Clinically, Salzmann’s degeneration appears as an accumulation of bluish-white superficial nodules in the mid-peripheral cornea. Generally, the eye is not inflamed unless there is associated corneal erosion. In that event, there will be limbal injection, corneal edema, and an anterior chamber reaction.

There are conflicting reports regarding the laterality of Salzmann’s degeneration; an older study reports a unilateral presentation in 80 percent of cases, while a more recent study suggests a bilateral predilection in 80 percent. The condition is seen more frequently in women than in men.

Patients with Salzmann’s degeneration usually describe a previous episode of ocular inflammation, often in childhood. Associated disorders may include phlyctenular disease, vernal keratoconjunctivitis, trachoma, or interstitial keratitis. Patients with a history of epithelial basement membrane dystrophy or corneal surgery may also be at increased risk.

At the cellular level, the nodules seen in Salzmann’s degeneration represent clumped masses of collagen fibrils anterior to Bowman’s membrane. Experts speculate that these peripheral accumulations of collagen are produced by fibroblasts within the conjunctiva or limbal vessels. In some cases, transmission electron microscopy has demonstrated reduplication of the epithelial basement membrane. Descemet’s membrane and the corneal endothelium are characteristically unaltered, however.

One theory behind the development of Salzmann’s degeneration suggests that the inciting corneal inflammation creates an irregular surface, allowing for uneven tear film distribution and exposure. A process known as hyalization ensues, which is the same process responsible for the development of conjunctival pinguecula. As the nodules grow in size, there is progressive damage and scarring at the level of Bowman’s membrane. This ultimately results in epithelial erosion and potential impairment of acuity.

Mildly asymptomatic cases of Salzmann’s degeneration may be managed with topical lubricants and/or a bandage contact lens. Prophylactic antibiosis is advisable if epithelial defects are significant. In more severe cases, superficial keratectomy may be utilized to remove the nodules from the anterior cornea. Phototherapeutic keratectomy (PTK) is also an option. If significant scarring is present, or if chronic epithelial breakdown makes the condition unmanageable, lamellar or penetrating keratoplasty may be the only recourse.

Clinical Pearls

The critical issue in managing Salzmann’s degeneration is proper diagnosis. Conditions such as band keratopathy, spheroid degeneration (climatic droplet keratopathy), and corneal keloids may all present with a similar clinical appearance. Consult a corneal specialist in those cases where diagnosis is elusive.

It may be tempting to use topical corticosteroids in Salzmann’s degeneration, particularly if the patient is symptomatic. However, since this condition is non-inflammatory in nature, steroids will have little effect. Additionally, the use of steroids introduces an unnecessary risk in patients with a compromised epithelium.

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