Hering's effect after unilateral ptosis surgery - if I correct my good eye will the originally operated on eye droop again?

You have had ptosis repair on your worse eye. What we have no idea is the degree of repair you have had. You may still have significant compensatory eyebrow elevation on the side that had ptosis repair. It is common to be under corrected with a lot of continued activation of compensatory mechanisms. Now you get your better side repaired, will these mechanisms continue to be as active or will there be relaxation of the compensatory mechanism? If so, it is possible that the recently repaired eyelid may also relax and be heavier after surgery. This is why I generally recommend repairing both eyelids at the same time.

Hi greetings from the UK. Yes you can develop contralateral consecutive ptosis in your previously operated eye but typically it's likely to be minimal. You can ask your surgeon to try to simulate it by performing a phenylephrine test.

Best Wishes
David