Blighted ovum: A fertilized ovum (egg) that did not develop or whose development ceased at an early stage, before 6 or 7 weeks of gestation. On the ultrasound examination of a blighted ovum, only the gestational sac that normally surrounds the embryo can be seen. There is usually no embryo inside the gestational sac. A blighted ovum is a form of early spontaneous abortion (miscarriage).
- Blind spot
Blind spot: In ophthalmology, a blind spot is: A small area of the retina where the optic nerve enters the eye; this type of blind spot occurs normally in all eyes. Any gap in the visual field corresponding to an area of the retina where no visual cells are present; this type of blind spot […]
Blind: 1. Unable to see. Without part or all of the sense of sight. 2. In a clinical trial, not to know the treatment given or received. The participant is not told whether they are in the experimental or control arm of the study. Also called masked.
- Blinded study
Blinded study: A study done in such a way that the patients or subjects do not know (is blinded as to) what treatment they are receiving to ensure that the results are not affected by a placebo effect (the power of suggestion).
Loss of useful sight. Blindness can be temporary or permanent. Damage to any portion of the eye, the optic nerve, or the area of the brain responsible for vision can lead to blindness. There are numerous (actually, innumerable) causes of blindness. The current politically correct terms for blindness include visually handicapped and visually challenged.
- Blindness, night
Blindness, night: Impaired vision in dim light and in the dark, due to impaired function of specific vision cells (namely, the rods) in the retina. The ability of our eyes to quickly view objects as they shift from light to dark areas and the ability to see in dim light or at night is an […]