a. In the 1 aor. opt. act. of ω-verbs the endings -ειας, -ειε, and -ειαν are more common than -αις, -αι, -αιεν.
b. In the aor. opt. passive of all verbs and in the opt. of μι-verbs and of contract verbs -ιτον, -ιτην, -ιμεν, -ιτε, -ιεν are commoner than -ιητον, -ιητην, -ιημεν, -ιητε, -ιησαν. Prose writers use either the shorter or the longer forms; poets use only the shorter forms. Except in contract verbs -ιητε is very common in the 2 pl. and is sometimes the only form in the Mss., as δοίητε, θείητε, γνοίητε, -βαίητε, λυθείητε, φανείητε; but the forms in question occur in prose writers and their genuineness is therefore unsupported by metrical evidence.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].