"I saw them with my own eyes!"

Translation: Viděl jsem je vlastníma očima!

[sir_dejf]

"Videl jsem je na vlastni oci" sounds more naturaly.

[VladaFu]

It is a more common idiom (and it is accepted), but "vlastníma očima" is not impossible (24 hits in the corpus, some of them with a slightly different meaning) and it is closer to the topic of this skill.

[sir_dejf]

This sounds like I saw them before my eyes transplant...

[VladaFu]

See https://goo.gl/ToFjSv

[sir_dejf]

I´m not saying that it is not possible to use it at all. But in this sentence, it sounds unnatural.

[ken55414]

Why isn't "Já jsem je vidět vlastníma očima" accepted?

[VladaFu]

You cannot use the infinitive here, you need the past participle (also called the l-participle).

[ken55414]

Thank you, my mistake!