( Here ( ( 's ( how ( ( a ( spherical ( contact lens ) ) ) ( corrects myopia ) ) ) ) . ) )
(ROOT (S (NP (RB Here)) (VP (VBZ 's) (SBAR (WHADVP (WRB how)) (S (NP (DT a) (JJ spherical) (NN contact) (NN lens)) (VP (VBZ corrects) (NP (NN myopia)))))) (. .)))
Here's how a spherical contact lens corrects myopia.
(ROOT (S (NP (JJ Concave) (NNS lenses)) (VP (MD can) (VP (VB correct) (NP (NN myopia)))) (. .)))