Metformin is usually started at a low dose and gradually increased to prevent brown trouser events
They shouldn't be in too much hurry to reduce it again as it's comparatively cheap and effective if it works for you and appears to have some cardiovascular protective benefits
The eye test thing seems to vary widely, my local optician is a first class guy and trained with and knows most of the local opthalmologists. I think he could have been one only he took over the family business instead.
He has a camera with a very powerful flash and reckons it doesn't require dilation - the instant results mean he can see if it's a poor photo and will only use the drops if he can't get a good pic without them. This means I can walk there and back (and have a good chat) without all the hassle of going to the hospital, hanging around for hours, paying an arm and a leg for the car park and having to wait until I can see before coming home again, quite a bargain! Plus he talks me through the pictures, and knows which specialist to refer to if he sees something. And he keeps the pictures on file to check for changes.
In other places even the opthalmologists don't have such sophisticated kit, and in yet other places the opticians are **** (I'm remembering a Two Ronnies sketch here!)