Double-blind: From 1 Different Sources
A type of controlled trial that tests the effectiveness of a treatment or compares the benefits of different treatments.
In double-blind trials, neither the patients nor the doctors assessing the treatments know which patients are receiving which treatment.
This eliminates any expectations about which treatment will be most effective.
A disorder in which abnormal FAECES occur as a result of a redundant loop in the small INTESTINE. The loop obstructs the normal ?ow of the contents of the bowel, causing stagnation. The syndrome is characterised by light-yellow, smelly, fatty, bulky faeces. The patient suffers from tiredness, malaise and loss of weight. Previous abdominal surgery is sometimes the cause, but the condition can be inherited. Blockage of intestinal contents upsets the bowel’s normal bacterial balance and hinders the normal absorption of nutrients. Treatment is either with antibiotics or, if that fails, surgery.... blind loop syndrome
See VISION – Defective colour vision.... colour blindness
A scienti?c study in which di?erent patients receive a di?erent drug, the same drug at a different dose, or a placebo – with neither the investigators assessing the outcome nor the subjects being treated knowing which of these the latter are receiving. The aim is to remove any hint of bias due to the investigators’ or patients’ preferences or preconceptions. The results are analysed after all the data have been collected and the code has been broken. Trials should have a separate supervising committee, the members of which know the code but do not take part in the study. Their job is to check the results at intervals so they can stop the trial if one arm of treatment is clearly better than another. Otherwise, it would be unethical to continue. (See INTERVENTION STUDY.)... double blind trial
See SQUINT.... double vision
See under BLINDNESS.... night blindness
Damage caused to the cornea of an unprotected EYE by the re?ection of the sun’s rays from snow. ULTRAVIOLET RAYS (UVR) are the damaging agent and people going out in snow and sunlight should wear protective goggles. The condition is painful but resolves if the eyes are covered with pads for a day or two. Prolonged exposure may seriously damage the cornea and impair vision.... snow blindness
A condition in which the patient sees better in a dim light or by night than in daylight. It is only found in conditions in which the light is very glaring, as in the desert and on snow, and is relieved by resting the retina (see EYE) – for example, by wearing coloured glasses for a time.... day blindness
See onchocerciasis.... river blindness
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.... blinding
See “blinding”.... single-blind trial
See “blinding”.... triple-blind trial
(in Britain) an incomplete list of persons who are technically blind or partially sighted due to reduced visual acuity, or who have severely restricted fields of vision (see blindness). Registration is voluntary, but it is a precondition for the receipt of some financial benefits. The list is maintained by local authorities (England and Wales), regional or island councils (in Scotland), or the Health and Social Care Board (Northern Ireland).... blind and partially sighted register
see intervention study.... blind trial
the principle that, where it is foreseen that a single action will have both a good and a bad outcome, a person may perform such an action provided that (a) he or she intends only the positive outcome, (b) the bad outcome is not disproportionate to the good, and (c) the good outcome is not a direct consequence of the bad. The classic example occurs where a terminally ill patient requires high doses of opiates for pain relief that may also depress respiratory function and hasten his or her death. In such a case the law holds that the doctor may supply the necessary dosage without this being considered tantamount to *euthanasia, even though the outcome will be the same, i.e. the morality of the action does not lie in its consequences (see consequentialism).... doctrine of double effect
a technique usually used in X-ray examinations of the bowel. Barium sulphate *contrast medium (first contrast) is used to coat the bowel wall. The bowel is then distended with gas (second contrast). The X-ray images obtained give exquisite detail of the lining of the gut. See also barium enema; barium swallow and meal.... double contrast
the situation in which a patient (the inducer) presents with delusional symptoms that he or she believes to be shared by someone else who is incapable of expressing them (typically a child or a pet). This is different from a *delusion by proxy, in which the inducer does not claim to be experiencing the symptoms himself or herself. The term was introduced in 2015 by Peter Lepping, Mark Rishniw, and Roland Wolfgang Freudenmann. Compare folie à deux.... double delusion
see stent.... double j stents
(DORV) a congenital defect of the heart in which both the aorta and the pulmonary artery arise predominantly from the right ventricle anterior to the ventricular septum with an associated *ventricular septal defect (VSD). The relationship between the site of the VSD and the great arteries must be taken into account for surgical repair. DORV can be associated with chromosomal defects.... double-outlet right ventricle
see uterus didelphys.... double uterus
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