( as ( , ( ( a ( plano-convex lens ) ) . ) ) )
(ROOT (FRAG (PP (IN as)) (, ,) (NP (DT a) (JJ plano-convex) (NN lens)) (. .)))
as, a plano-convex lens .
(ROOT (S (NP (NP (DT The) (NN lens)) (PP (IN of) (NP (DT the) (NN eye)))) (VP (VBZ is) (S (NP (DT a) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN convex)) (VP (VB shape)))) (. .)))