Eyestalk

Pulmonate land snails usually have two sets of tentacles on their head: the upper pair have an eye at the end; the lower pair are for olfaction.

A stalk-eyed fly

In anatomy, an eyestalk (sometimes spelled as eye stalk or known as an ommatophore) is a protrusion that extends the eye away from the body, giving the eye a better field of view than if it were unextended. It is common in nature and in fiction.

In nature

Well-developed eye of Eustrombus gigas on eyestalk. There is a small tentacle on the eyestalk also.

In nature, eyestalks are sometimes called tentacles, and may have olfactory organs and/or eyes at the end. Examples include snails, the trilobite superfamily Asaphoidea, and fly family Diopsidae. The crustacean family Polychelidae have eyestalks but no eye.

In fiction

A beholder is a fictional character that sports numerous vertical eyestalks. Many Dalek variants have a horizontal eyestalk.

Tripods from Star Wars have eyestalks.