Multifocal corneal argyrosis after an explosion injury

Case Report: In Vivo Confocal Microscopic Appearance of Corneal Argyrosis

SIGNIFICANCE

This report details the natural history of corneal argyrosis over 3 years using in vivo confocal microscopy to document regression of hyperreflective deposits, as well as effects on corneal nerves and endothelial cell morphology.

PURPOSE

To report the in vivo confocal microscopic features and clinical characteristics of a case of bilateral corneal argyrosis.

CASE REPORT

A 52-year-old man referred to us 3 months following cautery of the palpebral conjunctiva of both eyes with a silver nitrate stick was observed over the course of 3 years, during which slit-lamp photography and in vivo confocal microscopy were performed. At the first visit, slit-lamp examination showed a light blue-green discoloration and a thick, yellow, oval discoloration in the right and left cornea, respectively. One year later, under slit-lamp examination, the right cornea appeared nearly transparent, and the discoloration in the left cornea had remarkably regressed. In vivo confocal microscopy done at that time showed highly reflective deposits in Descemet membrane of the right cornea and throughout Bowman layer, the stroma, and Descemet membrane of the left cornea. Three years later, no accumulation of silver was observed during slit-lamp examination of either eye. In vivo confocal microscopy of the right cornea did not reveal any silver deposits, and the corneal structure appeared normal. In the left cornea, some silver deposits were still evident in Descemet membrane, and alterations of corneal nerve and endothelial cell morphology were also evident.

CONCLUSIONS

This report reviews the 3-year natural history of a patient with corneal argyrosis. In vivo confocal microscopy demonstrates that over time the corneal argyrosis gradually resolves without any treatment. However, the presence of silver in the cornea may impact the corneal nerves and endothelial cells.

Diagnostic methods in ocular argyrosis: case report

Purpose

The aim of this report is to present a case of a patient, metal foundry worker, who had been exposed to industrial silver salts for over 20 years. It is well established that chronic exposure to silver compounds can cause accumulation of silver deposits in various tissues. This condition is referred to as argyrosis or argyria, whereas changes related to eye tissues are defined as ocular argyrosis.

Methods

A complete eye examination, corneal confocal microscopy, kinetic and static visual field test, posterior segment optical coherent tomography, pattern visual evoked potentials (PVEP), flash visual evoked potentials, multifocal electroretinogram, pattern electroretinogram (PERG), full-field electroretinography (FERG) and electrooculogram were all performed.

Results

Eye examination revealed decreased visual acuity, corneal deposits and drusenoid changes within the macula. Although electrophysiology tests did not show changes in the function of retinal pigment epithelium, they revealed abnormal function of photoreceptors in the central and peripheral retina. PERG abnormalities and delayed latency of P100 wave in PVEP confirmed impaired function of the inner layers of the retina in the macular region.

Conclusions

Corneal confocal microscopy and electrophysiological tests may help confirm the diagnosis of ocular argyrosis.

A pharmacological and toxicological profile of silver as an antimicrobial agent in medical devices

Silver is used widely in wound dressings and medical devices as a broad-spectrum antibiotic. Metallic silver and most inorganic silver compounds ionise in moisture, body fluids, and secretions to release biologically active Ag(+). The ion is absorbed into the systemic circulation from the diet and drinking water, by inhalation and through intraparenteral administration. Percutaneous absorption of Ag(+) through intact or damaged skin is low. Ag(+) binds strongly to metallothionein, albumins, and macroglobulins and is metabolised to all tissues other than the brain and the central nervous system. Silver sulphide or silver selenide precipitates, bound lysosomally in soft tissues, are inert and not associated with an irreversible toxic change. Argyria and argyrosis are the principle effects associated with heavy deposition of insoluble silver precipitates in the dermis and cornea/conjunctiva. Whilst these changes may be profoundly disfiguring and persistent, they are not associated with pathological damage in any tissue. The present paper discusses the mechanisms of absorption and metabolism of silver in the human body, presumed mechanisms of argyria and argyrosis, and the elimination of silver-protein complexes in the bile and urine. Minimum blood silver levels consistent with early signs of argyria or argyrosis are not known. Silver allergy does occur but the extent of the problem is not known. Reference values for silver exposure are discussed.

Critical Observations on the Neurotoxicity of Silver

Silver is a xenobiotic element with no recognized trace metal value in the human body. It is absorbed into the body through the lungs, gastrointestinal tract, mucus membranes of the urinogenital tract, and through the skin, mainly in the form of silver protein complexes. Although silver is metabolized throughout the soft tissues, available evidence from experimental animal studies and human clinical reports has failed to unequivocally establish that it enters tissues of the central nervous system or is a cause of neurotoxic damage. Argyria characterized by deposition of particles of silver sulfide or silver selenide is the principle contraindication for using silver in medical devices or occupationally. This presents discoloration of the skin but is not regarded as a health risk or manifestation of toxicity. No evidence is available to demonstrate the toxic risk of silver to the peripheral nervous system, although silver sulfide deposits have been identified in the region of cutaneous nerves. Transitory silver sulfide deposits seen in the tissues of the blood-brain and blood-CSF barriers are mostly lysosomally bound or deposited on basement membranes or collagen without toxic effect. Silver is mostly excreted from the body in the urine and feces. Further research is indicated to evaluate the role of metal binding proteins including metallothioneins as cytoprotectants for neurological tissue.

Application of energy-dispersive X-ray microanalysis on the diagnosis of atypical calcific band keratopathy

We describe pathological, ultrastructural, and spectrographic analyses of surgically resected cornea from a man with atypical corneal opacification, and discuss the corneal pathogenesis, and the utility of energy-dispersive X-ray microanalysis (EDXA). The histopathologic features of a case presenting with longstanding bilateral corneal clouding are reported, which was difficult to be diagnosed clinically as calcific band keratopathy. The patient underwent keratoplasty on his right eye. Paraffin sections of the host corneal button were subjected to hematoxylin and eosin (H&E). An adjacent section was studied by means of EDXA. Plastic sections were observed under a transmission electron microscope (TEM). H&E staining revealed flattened corneal epithelial cells and disappearing Bowman's membrane accompanied by numerous basophilic granular deposits within the underlying corneal stroma. EDXA demonstrated the elevated peaks of calcium and phosphorus within the area of granular deposits. TEM revealed electron dense material consistent with extracellular calcospherites. Given the patient's past medical and family history, and the serologic test results, the clinical presentation and histological findings were most consistent with calcific band keratopathy associated with preexisting minimal syphilitic keratitis. Extensive histologic studies including EDXA on resected corneal tissue can be helpful for the differential diagnosis and may elucidate the pathogenesis of corneal diseases.