Purblind vs synonym

…the man was a purblind man led by a small boy. Please, I want the meaning of the bolden text

Old age is a synonym to death.
Please, is it grammatical to construct the above? I heard it from a radio presenter.

‘purblind’ having impaired or defective vision. This is not a common term.

Old age is a synonym for death would be grammatical. However it would not be factually correct.