Ocular Surface Pathology in Patients Suffering From Mercury Intoxication Is Consistent With Neurogenic Dry Eye Disease

Abstract Purpose: To report ocular surface pathology of patients with acute/subacute mercury intoxication.Methods: Male workers intoxicated with inorganic mercury were examined for dry eye (DE)-related symptoms. Examinations included Ocular Surface Disease Index questionnaire; tear osmolarity, tear break-up time (T-BUT) and production; mechanical and thermal corneal sensitivity; corneal nerve and dendritic cell density analysis; and analysis of 23 tear cytokines.Results: Most patients, 63.6%, had severe DE-related symptoms. Tear osmolarity was elevated in 83.4%, and T-BUT was low in 22.7% of patients. Tear production and tear lysozyme concentration were low in 13.6% and 27.3% of cases, respectively. Corneal sensitivity thresholds for mechanical, heat and cold stimuli were higher than controls. Densities of nerves, nerve branching, and dendritic cells were lower than in controls. Patient tear levels of IL-12p70, IL1-RA, RANTES, and VEGF were increased, whereas EGF, IL-6, and IP-10/CXCL10 were decreased. Based on cytokine levels, two clusters of patients were identified. Cluster 2 patients had significantly increased tear levels of 18 cytokines, decreased tear lysozyme, lower nerve branching density, fewer dendritic cells, and higher urine mercury levels.Conclusions: Mercury poisoning produced previously undescribed ocular surface pathology, similar to neurogenic inflammatory type of DE and different from the more common DE subtypes.