We get a bit of entropion - it seems to be relatively common in Texel-type sheep.
Usually rinsing the eye and turning it back a couple of times works. If mum is dirty underneath, get her cleaned or the eye will get more dirt in it and become quite sore, even infected.
If it's still inverting, or where the lamb is in the field and I am not going to be able to catch it several times, then yes I do pinch the lower lid, just enough to make it swell very slightly. I hardly ever need to do more than this.
Where the above has failed, an injection of a specific antibiotic (can't remember which but your vet will know) in the inside of the lower lid will give the required swelling and also protect against any infection. If you have small numbers of sheep, get the vet to do this for you. If you have this a lot, it's worth getting the vet to show you how and buying the antibiotic and very fine needles in. (And changing your tup.)
In the worst case, where the condition has been missed in the field, the lamb may form a cataract where the eyelashes have scratched the cornea. If you see it at this stage you can get a soothing antibiotic cream to apply to the eye. But they do always seem to heal eventually, and be quite normal by the time they are grown.
And yes, in these parts a tup is a male uncastrated sheep. The term 'ram' is used only by townies and southerners!

And, curiously, in the case of the Kelso Ram Sales.
