Rename just layers that are turned on

How do i modify the following routine to rename just the layers that are currently turned on?

;Adds a specified layer prefix to all layers

(defun C:lprefix ()
(vl-load-com)
(setq pre (getstring "\nEnter Layer Prefix : "))
(setq doc (vla-get-activedocument
(vlax-get-acad-object)
)
layers (vla-get-layers doc)
)
(vlax-for lay layers
(setq lname (vla-get-name lay))
(if (not (member lname '("0" "Defpoints")))
(vla-put-Name lay (strcat pre lname))
)
)
)
(princ)

 

(if (and
(not (member lname '("0" "Defpoints")))
(eq :vlax-true (vla-get-layeron lay))
)
(vla-put-name lay (strcat pre lname))
)

 

thanks so much for your help!