[A familial anterior corneal degeneration: clinical aspects, histopathology and differential diagnosis]

[Salzmann nodular degeneration: pathogenesis, clinical characteristics and treatment]

Salzmann nodular degeneration (SND) is a rare non-inflammatory disease observed primarily in middle-aged women. The disease generally occurs in patients with chronic inflammation of the anterior ocular surface. Its etiopathogenesis remains poorly investigated. This literature review describes clinical manifestations, risk factors and diagnostic methods, evaluates the effectiveness of different therapeutic and surgical treatment methods. Understanding of the pathogenetic mechanisms, precise diagnosis and identification of the risk factors can help clinical physicians make the optimal choice of treatment strategy and achieve the best clinical outcomes.

Salzmann's nodular degeneration

Salzmann nodular corneal degeneration is a non-inflammatory, progressive corneal degeneration characterized by bluish-white nodules of varying shapes classically located in the mid-peripheral cornea. It was first described by Maximilian Salzmann in 1925 and was noted at that time to be associated with "eczematous keratoconjunctivitis". Since then, significant progress has been made to understand environmental and genetic risk factors associated with SND. However, etiopathogenesis remains poorly understood. A review of the literature was performed to highlight our recent understanding of SND and its management.

Salzmann nodular degeneration: prevalence, impact, and management strategies

Purpose

This review will summarize the clinical and histological presentation of Salzmann nodular degeneration (SND), its prevalence and risk factors, potential underlying mechanisms, diagnostic tools, management options, and impact on cataract surgery and co-morbid ocular surface diseases.

Method

PubMed review of 44 articles published between 1976 and 2018.

Results

SND is a corneal disease characterized by whitish gray or bluish nodules on the peripheral or central cornea. The clinical presentation of SND is variable and the nodules can be asymptomatic or cause foreign body sensation and/or blurred vision. Histologically, SND appears as subepithelial nodules with thin overlying epithelium, disrupted or absent Bowman’s layer, and activated fibroblasts within the nodule. SND pathogenesis is not fully understood but is thought to involve poor epithelial protection and disruption of the epithelial–stromal interface, allowing for penetration of epithelially derived growth factors into the stroma and subsequent activation of stromal fibroblasts, eventually leading to sub-epithelial deposition of disorganized extracellular membrane components. SND most commonly occurs in Caucasian females in a bimodal distribution, occurring in the fifth or eighth and ninth decades of life. Risk factors for SND include ocular surface diseases and surgery. Surgical intervention is recommended in individuals with symptomatic nodules – primarily superficial keratectomy performed with or without intraoperative mitomycin C, photokeratectomy, and/or amniotic membrane transplantation. These procedures have been successful in removing the lesion and reducing corneal irregularity, but have variable recurrence rates (0–31%).

Conclusion

The pathogenesis of SND is complex and multifactorial. Advances in diagnostic and treatment modalities have allowed for earlier and more accurate diagnosis and effective treatment of SND.

Salzmann's nodular degeneration of the cornea: a review and case series

Salzmann's nodular degeneration is a rare, noninflammatory, slowly progressive, degenerative condition. Bluish-white nodules raised above the surface of the cornea characterize it. It has usually developed in corneas with a history of phlyctenulosis, trachoma, vernal keratoconjunctivitis, measles, scarlet fever, and various other viral diseases. However, today the majority of cases have been seen without recognized previous keratitis. It is composed of dense irregularly arranged collagen tissue with hyalinization between epithelium and Bowman's layer or beyond. Manual removal, phototherapeutic keratectomy (PTK) with or without the use of topical mitomycin-C, lamellar or penetrating keratoplasty have been used in the treatment of this disease. Salzmann's nodular degeneration does not seem to consist of one clinical entity. In some cases, elevated and pannus-like tissue can be separated easily from the corneal surface leaving Bowman's layer almost untouched. In these eyes, subsequent PTK may be necessary to smooth the surface. Recurrences are rare in these eyes. In contrast, some eyes (often with major peripheral vascularization) are left with deep defects in Bowman's layer and superficial stroma after difficult mechanical removal of nodules. In these eyes, multiple masking/laser ablation procedures are mandatory to acquire a homogenous surface. In our experience, the required laser ablation depth is significantly greater and the best-corrected visual acuity to be expected is reduced in contrast to the eyes with easy removal of the nodules. In these eyes recurrences seem to occur more frequently after treatment. Of 35 eyes documented to have Salzmann's nodular degeneration during the last 15 years in our department, 22 needed PTK treatment. Visual acuity increased from 0.4 to 0.7 on average. As a routine, laser ablation should be combined with previous conventional removal of nodules and excessive pannus tissue. By doing so, lamellar and penetrating keratoplasty techniques are hardly ever required in those eyes.