Eye movements examination

[Convalaria]

Question..
How can asking to adduct and move eye down check superior oblique musle, if it functions to depress and abduct?

And the same thing with:
inferior oblique m. - by asking to adduct and move down (when it functions to elevate and abduct)
superior rectus m. - by asking to abduct and move up (when it functions to elevate and adduct)
inferior rectus m. - by asking to abduct and move down (when it functions to depress and adduct)

Is it me and 1am or it really seems illogical?

Thanks!

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[ijn]

The reason is that each of the depressors has an ideal orientation that it functions at. When you adduct the eye, the inferior rectus is out of ideal alignment so it cannot exert a strong depressing force. Similarly, when you abduct the eye, the superior oblique is out of ideal alignment so it cannot exert a strong depressing force. This allows you to test each muscle in isolation.