( There ( ( are ( ( 2 types ) ( of ( ( ( ( lenses , ) ( a convex ) ) and ) ( concave lens ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD 2) (NNS types)) (PP (IN of) (NP (NP (NNS lenses)) (, ,) (NP (DT a) (NN convex)) (CC and) (NP (JJ concave) (NN lens)))))) (. .)))
There are 2 types of lenses, a convex and concave lens.
(ROOT (S (NP (JJ Concave) (NNS lenses)) (VP (MD can) (VP (VB correct) (NP (NN myopia)))) (. .)))