( ( If ( you ( look ( at ( ( the sun ) ( ( ( too long ) and ) ( too hard ) ) ) ) ) ) ) ( you ( ( can ( ( ( damage ( your retina ) ) and ) ( cause ( permanent ( blind spots ) ) ) ) ) . ) ) )
(ROOT (S (SBAR (IN If) (S (NP (PRP you)) (VP (VBP look) (PP (IN at) (NP (NP (DT the) (NN sun)) (ADJP (ADJP (RB too) (JJ long)) (CC and) (ADJP (RB too) (JJ hard)))))))) (NP (PRP you)) (VP (MD can) (VP (VP (VB damage) (NP (PRP$ your) (NN retina))) (CC and) (VP (VB cause) (NP (JJ permanent) (JJ blind) (NNS spots))))) (. .)))
If you look at the sun too long and too hard you can damage your retina and cause permanent blind  spots.
(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)))) (. .)))