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Maria Miranda, Inmaculada Almansa, Javier J. Araiz, Violeta Sanchez-Vallejo, Roberto Gimeno-Hernández, Francisco Javier Romero, Dolores Silvestre; Lipid Peroxidation Is Increased In Tears From The Elderly. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4244.
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Tear film, composed of lipid, aqueous and mucin layers, protects tissues by functioning as antioxidant, providing lubrication, and inhibiting bacterial adherence. The major function of tears is to maintain corneal health by diluting, or neutralizing foreign chemicals and reactive oxygen species. Several low-molecular-weight antioxidants have been found in human tears, including cysteine, glutathione, urate, and tyrosine and dietary ascorbate. The Schirmer's test is commonly used in the clinic for the diagnosis of dry eye disease by measuring tear volume. The main purpose of this study is to describe a procedure which can be used to recover tears from the Schirmer strip for the measurement of a lipid peroxidation marker: malondialdehyde (MDA), and glutathione (GSH), and to compare the concentration of these compounds in two age groups: 18 to 30 years and 60 to 80 years.
The study was approved by the Ethics Committee of the institution and adjusted to the Spanish law. Two group of subjects aged 18 to 30 years and 60 to 80 years were recruited and signed an informed consent. A Schirmer strip was placed onto the outer canthus of the eye of each subject, and reflex tears were collected for 5 minutes. Subjects also answered a questionnaire about smoking, alcoholic beverages, fruits, and vegetables comsumption, and about the use of vitamins and / or drugs and exercise. MDA was assayed in tears with a modified method from Richard where the complex formed between MDA and thiobarbituric acid was detected with HPLC (Romero et al., 1998). GSH content was quantified by the method of Reed et al. (1980). The protein content was assayed as described by Lowry et al. (1951)
Results showed that MDA in tears from older subjects was significantly increased than that from younger subjects. GSH and protein content was decreased in tears from the older groups. There was a significant difference in the tear flow rates between the two groups with the younger group having a higher flow rate.
The antioxidant and/or lipid peroxidation status of tear fluid is of interest, because tears constitute the first barrier protecting the cornea against oxidative damage and it is altered in older subjects.
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