Light filters for the blind (5)

I believe the answer is:

slats

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'light filters' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Maybe there's a link between them I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Another definition for slats that I've seen is " Thin strips of wood or metal".)

I've seen this clue in The Globe and Mail.

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