Wudasie Mamo Daba lost her vision 25 years ago with an unknown cause. Her two sons are also blind. Loss of vision is considered sudden if it develops within a few minutes to a couple of days. It may affect one or both eyes and all or part of a field of vision. Loss of only a small part of the field of vision (for example, as a result of a small retinal detachment) may seem like blurred vision.