Yes... but the original question merely asked about the modified treble clef with an 8 incorporated (one way or another) into the bottom loop, most frequently found in vocal scores in my experience - as it happens, I have a copy of Handel's Messiah which uses it as the Tenor Clef, and agree that it is much easier to read than the 'K' tenor clef.

8va is used in the same manner as dynamic markings such as ff, pp and so on, but this is an actual clef we're talking about, not an instruction. Let's not get ourselves confused, eh?! ;o)