What is characterized by symptoms such as a constant buzzing or ringing in the ear?

The condition characterized by symptoms such as a constant buzzing or ringing in the ear is tinnitus. Tinnitus is often described as the perception of sound when no external sound is present, which can manifest as ringing, buzzing, hissing, or other sounds. This sensation can be temporary or chronic and is commonly associated with hearing loss, exposure to loud noises, or ear problems.

In contrast, astigmatism refers to a common vision condition caused by an irregularly shaped cornea or lens, leading to blurred vision. Anosmia is the loss of the sense of smell, which is unrelated to any auditory symptoms. Analgesia refers to the inability to feel pain, typically due to medication or medical condition, and does not correspond to any auditory phenomena either. Thus, the defining features of tinnitus clearly distinguish it from the other conditions listed.