, when it functions as a predicate adjective: hyphenate Light-adapted retinal slices... do not hyphenate The retinal slices were light adapted...
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AP Style manual: (http://www.apsstylemanual.org/oldmanual/mechanics/hyphens.htm)
Do not use a hyphen when a normally hyphenated compound adjective follows a linking verb and does not precede a noun; i.e., when it functions as a predicate adjective:
hyphenate
Ligh