Tendon-driven　continuum　robots　(TDCRs)　with　mechanical　compliance　have　gained　popularity　in　natural　orifice　transluminal　endoscopic　surgery　(NOTES).　Teleoperation　problems　of　the　TDCRs　involve　performance　objectives　in　addition　to　the　visibility　constraint.　Handling　the　coupling　between　potentially　conflicting　objectives　and　the　visibility　constraint　remains　challenging　for　surgeons　when　operating　TDCRs.　This　paper　presents　a　shared　control　method　to　assist　in　the　teleoperation　of　the　TDCRs,　which　guarantees　visual　targets　remain　within　the　field　of　view　(FoV)　of　the　TDCR.　The　visibility　constraint　is　explicitly　defined　using　a　zeroing　control　barrier　function,　which　is　specified　in　terms　of　the　forward　invariance　of　a　visible　set.　To　ensure　accuracy,　the　Jacobian　matrix　of　the　system　is　approximated　online　using　sensing　data.　Then,　the　visibility　constraint,　along　with　the　robot＇s　physical　constraints,　is　integrated　into　a　quadratic　program　(QP)　framework.　This　allows　for　the　optimization　of　the　control　input　of　the　operator　subject　to　constraints,　thus　preserving　visibility.　Finally,　simulations　and　experiments　were　conducted　to　demonstrate　the　effectiveness　of　the　proposed　approach　under　two　teleoperation　modes.　The　results　show　that　the　proposed　method　achieved　a　reduction　of　approximately　70%　in　ITP　and　43%　in　MAE　compared　to　direct　teleoperation.