Yes, ASTIGMATIC is a Scrabble word!

Letter values in Scrabble US: A 1, S 1, T 1, I 1, G 2, M 3, A 1, T 1, I 1, C 3.

Is it a valid word?

ASTIGMATIC is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

of or relating to a defect in the eye or in a lens caused by a deviation from spherical curvature which prevents light rays from meeting at a common focus and so results in distorted images