The concealment of group assignment (to either the treatment or control group) from the knowledge of participants and/or investigators in a clinical trial. Blinding eliminates the possibility that knowledge of assignment may affect individual response to treatment or investigator behaviours that may affect outcomes. Blinding is not always practical (e.g. when comparing surgery to drug treatment) but it should be used whenever it is possible and compatible with optimal care. There are various kinds of blinding: single-blind trial: one in which knowledge of group assignment is withheld only from participants double-blind trial: one in which the knowledge is withheld from participants and investigators triple-blind trial: one in which the knowledge is withheld from participants, investigators and those assessing outcomes of the assignment.
In general, any factor that distorts the true nature of an event or observation. In clinical observations, a bias is any systematic factor other than the intervention of interest that affects the magnitude of an observed difference (i.e. trends to increase or decrease) in the outcomes of a treatment group and control group. Bias diminishes the accuracy (though not necessarily the precision) of an observation. Randomization is a technique used to decrease this form of bias. Bias also refers to a prejudiced or partial viewpoint that would affect someone’s interpretation of a problem. Double-blinding is a technique used to decrease this type of bias. See “blinding”.... bias
This is a blinding eye disease, almost exclusively of infants and young children, which results from vitamin A deficiency, associated with protein-calorie-malnutrition. Xerophthalmia literally means ‘dryness’ of the conjunctiva.... xerophthalmia
(bullous pemphigoid) n. a chronic itchy blistering disorder most common in the elderly. The blisters most commonly occur on the limbs and may persist, unlike those of *pemphigus. Pemphigoid is an *autoimmune disease and responds to treatment with corticosteroids or immunosuppressant drugs. Ocular pemphigoid is a potentially blinding disease in which there is dryness, blistering, and scarring of the conjunctiva, leading to shortening of the *fornices due to adhesions (*symblepharon).... pemphigoid
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