<unk> , often abbreviated to<unk><unk> ", is a term used in various mental health services, prisons and special schools to describe the status of a prisoner or patient who poses a threat to himself or a third party, and must therefore be kept under<unk><unk> .
There are essentially two levels of<unk> s. The highest level, employed only for those patients who are considered to be extremely high risk to either themselves or a third party, involves a care worker remaining within arms reach of the service user at all times. The second level involves only maintaining a<unk>  watch on a patient, sometimes from a distance.<unk> s have been criticised by many service user groups.
Constant visual observation
Cranial electrical stimulation
Rapid Visual Imaging
Brain mapping
Neurological examination
Eye pain laboratory tests
Transcranial magnetic stimulation
Peripheral vascular examination