( ( The catalog ) ( ( ( shows ( such ( a lens ) ) ) ( with ( ( ( center ( thickness ( 9.1 mm ) ) ) , ) ( ( edge thickness ) ( 1.5 mm ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN catalog)) (VP (VBZ shows) (NP (PDT such) (DT a) (NN lens)) (PP (IN with) (NP (NP (NN center) (NN thickness) (NNP 9.1) (NNP mm)) (, ,) (NP (NP (NN edge) (NN thickness)) (NP (CD 1.5) (NN mm)))))) (. .)))
The catalog shows such a lens with center thickness 9.1mm, edge thickness 1.5mm.
(ROOT (S (NP (DT A) (JJ concave) (NN lens)) (VP (VBZ is) (NP (NP (JJR thicker)) (PP (IN at) (NP (DT the) (NNS edges)))) (SBAR (IN than) (S (NP (PRP it)) (VP (VBZ is) (PP (IN in) (NP (DT the) (NN middle))))))) (. .)))
A concave lens is thicker at the edges than it is in the middle.