( However ( , ( ( extreme caution ) ( ( should ( be ( ( used , ) ( as ( ( ( looking directly ) ( at ( the Sun ) ) ) ( can ( cause ( permanent ( eye damage ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB However)) (, ,) (NP (JJ extreme) (NN caution)) (VP (MD should) (VP (VB be) (VP (VBN used) (, ,) (SBAR (IN as) (S (S (VP (VBG looking) (ADVP (RB directly)) (PP (IN at) (NP (DT the) (NNP Sun))))) (VP (MD can) (VP (VB cause) (NP (JJ permanent) (NN eye) (NN damage))))))))) (. .)))
However, extreme caution should be used, as looking directly at the Sun can cause permanent eye damage.
(ROOT (S (S (VP (VBG Looking) (ADVP (RB directly)) (PP (IN at) (NP (DT the) (NN sun))))) (VP (MD can) (VP (VB cause) (NP (NN blindness)))) (. .)))