( ( A ( small ( gas bubble ) ) ) ( ( may ( be ( ( placed ( inside ( the eye ) ) ) ( to ( help ( seal ( a ( macular hole ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (JJ small) (NN gas) (NN bubble)) (VP (MD may) (VP (VB be) (VP (VBN placed) (PP (IN inside) (NP (DT the) (NN eye))) (S (VP (TO to) (VP (VB help) (VP (VB seal) (NP (DT a) (NN macular) (NN hole))))))))) (. .)))
A small gas bubble may be placed inside the eye to help seal a macular hole.
(ROOT (S (NP (NNP Gas) (NN bubble) (NNS holes)) (VP (VBZ helps) (NP (NP (JJ pumice) (NN float)) (PP (IN in) (NP (NN water))))) (. .)))