Good bye by Bill Knott

If you are still alive when you read this
Close your eyes. I am
Under their lids, growing black

On this poem, I wonder structure of 'I am under their lids, growing black'

is it 'I am under their lids, as I am growing black'(adverb phrase)?

and 'If you are still alive when you read this Close your eyes' is

'If you are still alive(adverb clauses of condition) when you read this(adverb clauses of time), close your eyes(imperative sentence)'

so are 'adverb clauses of condition'and 'adverb clauses of time' used on one

sentece?