That's an odd symptom. I've had that a few times, and didn't relate it to INR being too low. I get ocular migraines. I've been getting them for decades. I associated the gray 'cloud' to something related to the ocular migraine -- blood pressure or something - rather than an INR that is too low.
The next time I get one of those things, I'll double-check my INR. (Although I've had one TIA, I didn't associate that visual thing to INR - it seemed like a scary, temporary neurological event rather than a permanent visual disturbance or something related a thrown clot)