Is it still natural to change "at first hand" into "directly" this sentence?

[eggcracker]

Is it still natural to change "at first hand" into "directly" this sentence?

The President visited the area to see the devastation at first hand.
Is it natural and grammatical to change "at first hand" into "directly" or "on his eyes" above sentence?

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[billmcd]

Re: Is it still natural to change "at first hand" into "directly" this sentence?

The President visited the area to see the devastation at first hand.
Is it natural and grammatical to change "at first hand" into "directly" or "on his eyes" above sentence?

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My first preference would be "first hand" ("at" is not necessary).
"Directly" is OK.
"On his eyes" is not a correct term, but you could use "with his own eyes".