Ocular Pathology

Anatomy and pathology of the human eye. Use it to review eye pathology for Ophthalmology Board Review or OKAP.

About Mission for Vision

Saturday, February 17, 2007

Salzmann’s Nodular Degeneration of the Cornea

Definition: This clinical entity was described in 1925 by Maximilian Salzmann in the German literature as usually following trachoma or phlyctenular keratitis. It is characterized by multiple superficial blue white nodules in the midperiphery of the cornea. Recently the pathologic hallmark has been claimed to be the deposition of oxytalan elastic microfibils (Reference 2).
Incidence/Prevalence: Considered rare. The published age range is wide, 4-70, and there is not a clear gender predilection although some series found the disease was predominant in middle aged women (Reference 1).
Etiology: Salzmann's nodular degeneration has been associated with trachoma, interstitial keratitis, vernal keratoconjunctivitis, phlyctenular keratoconjunctivitis, ocular trauma, measles, scarlet fever, and previous surgery. The condition may be considered a special form of corneal scarring whose pathogenesis is unknown. It may very well be one final common pathway of corneal scarring. Oxytalan fibers are presumably one of the three types of elastic fibers: oxytalan, elaunin, and elastin. Oxytalan fibers presumably occur early in elastogenesis and can be segregated from mature elastic fibers by the oxidized aldehyde fuchsin stain (see below). Oxytalan fibers have been identified in cornea scarring from many causes including trauma, keratoconus, and anterior staphyloma (also non-specific).
Clinical Findings: Most often Salzmann's nodular degeneration is unilateral, but it may be bilateral with single or multiple lesions that usually measure between 1-3 mm in size. There may be an accompanying iron line. Usually asymptomatic but patients may develop recurrent corneal erosions or decreased vision from scarring. The nodules are sometimes arranged in a spokelike pattern (numbers 1 in the image).
Histopathology: Sections of the cornea show thinning of the epithelium or denudation as shown above (arrow 1), destruction of Bowman’s layer (number 2 above and arrow 1 below), duplication of the epithelial basement membrane and disorganization of collagen lamellae in the superficial anterior stroma (number 2). These histologic findings are entirely non-specific and can be seen in scarring from any cause. Some authors have touted the oxidized aldehyde fuchsin stain to identify blue violet coloring in the stromal oxytalan fibers (arrows 2 below). Tendon serves as a good control tissue in the same block. Oxytalan fibers are aggregates of fibrillar material. Ultrastructurally, there are aggregates of electron dense collections of small microfibrils (white arrows 3). They are quite small 10 nm in diameter. The tubular appearance in cross sections requires magnification on the order 72-100 thousand times on the electron microscope for identification. Comparison to larger collagen fibrils is helpful (number 4). Consideration should be given to placing the specimen in a solution of glutaraldehyde/paraformaldehyde prior to the biopsy.
Treatment: Medical therapy consists of lubrication, warm compresses, lid hygiene, topical steroids, and/or oral doxycycline and has been successful in over half of the patients in some series. In cases in which vision is compromised or there is discomfort unremedied by medical therapy, the nodules may be removed by superficial, lamellar or penetrating keratectomy depending on their extent. Excimer laser has been used to smooth the surface after removal.
1. Farjo et al Cornea 2006.
2. Obata H et al. Cornea 2006

<< Home