A groove is formed in {HEAD ~ an endpiece head} to allow {TAIL ~ distal ends} of the head to flex away from the lens and reduce the pressure on the lens 
to allow
A groove is formed in { HEAD ~ an endpiece head } to allow { TAIL ~ distal ends } of the head to flex away from the lens and reduce the pressure on the lens
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH