Abstract
BackgroundThere are few clinical data on retinal involvement after acute exposure to high concentrations mercury and the available reports are based on a small number of patients suffering chronic exposure. The purpose of this paper is to report findings in workers acutely exposed to very high concentrations of mercury vapor with the aim of providing data on a possible direct retinal involvement.MethodsTwenty-nine patients and 16 controls were evaluated in a comparative case series. Mercury levels in blood and urine samples, visual acuity (VA), contrast sensitivity (CS), visual field (VF), color discrimination and optical coherence tomography (OCT) were recorded. The pattern reversal visual-evoked potentials (PRVEP), full-field and multifocal electroretinography (ffERG/mfERG), pattern electroretinography (PERG), systemic symptoms, presence of erethism, and electromyography (EMG) were also gathered. A descriptive analysis was performed. The correlations between variables also were studied.In addition, electrophysiological data from those patients with deeper VF defects (group 1) were compared with a normal control group.ResultsTwenty-six workers exhibited symptoms of erethism. The EMG showed sensorimotor polyneuropathy and multiple mononeuropathy. The VA was slightly affected in 48.27% (n = 14) of subjects. Loss of CS in at least one of four spatial frequencies and color vision alterations occurred in 96.5% (n = 28) and 44.8% (n = 13), respectively. VF alterations were identified in 72.4% (n = 21) patients. No morphologic changes were seen in the OCT scans. Latencies over 100 milliseconds and reduced amplitudes of P100 were found in the PRVEP (p < 0.05). The reduced amplitude of the b wave at the ffERG, of the P50 at the PERG and of the P1 wave at the mfERG results (p < 0.05) suggested that the outer retina was involved. Significant negative correlations among blood mercury levels, VA, and ffERG were observed.ConclusionsIn this case series, showed that acute exposure to mercury vapor had a hazardous effect on the visual system. Although neurologic and visual pathway involvement was clearly demonstrated, the differences found compared to control support the existence of a direct functional retinal damage and participation in impaired vision in mercury poisoning.
Highlights
There are few clinical data on retinal involvement after acute exposure to high concentrations mercury and the available reports are based on a small number of patients suffering chronic exposure
In this case series, showed that acute exposure to mercury vapor had a hazardous effect on the visual system
Neurologic and visual pathway involvement was clearly demonstrated, the differences found compared to control support the existence of a direct functional retinal damage and participation in impaired vision in mercury poisoning
Summary
There are few clinical data on retinal involvement after acute exposure to high concentrations mercury and the available reports are based on a small number of patients suffering chronic exposure. Episodes of acute or subacute poisonings as the result of exposure to elemental mercury in the workplace are uncommon Toxic metals such as mercury have been implicated in several neurological disorders [1,2,3,4] and have been thought to be responsible for several retinal and optic disorders because of their proximity to the Central Nervous System (CNS) and the proved neurotoxicity of this metal [5,6,7]. It is still unclear whether the eye tissues lesions are consequence of CNS affectation or derived from a direct effect. Some animal studies have reported the accumulation of mercury in vitreous, retina and the choroid after systemic administration [8, 9], but others have limited the presence of the metal to the retinal pigment epithelium (RPE) and external neuroretinal layers [10,11,12] that is, to the structures irrigated by the choroid.
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