They tried to make me have the eye drops when I went for eye screening the other day too, when I said they hadn't needed them the previous 3 or 4 times I was told it was a new policy, everyone had to have them. They couldn't explain why this new policy existed. I didn't have sunglasses with me so would have been stuck there for ages afterwards if they'd done the drops I assume, anyway I didn't let them do the drops and they said the images were OK.
There was a big warning sheet there about the eye drops, about how they can cause a pressure increase inside the eye which is an emergency and you should seek treatment if this happens. So of course I'm not going to let them use the eye drops!