But will there be any lagophthalmos and eyelid lag in downward gaze after other surgery is done? Since you mentioned that frontalis sling is done for severe ptosis, than i think im wrong. The doctor did not tell me the name of the surgery so it might not be frontalis sling i just thought it was frontalis sling.
You mention mild ptosis. Usually a frontalis sling is done for rather severe ptosis, with poor levator function of the upper lid. I would get a second opinion before having the surgery. Overcorrection and poor lid closure are risks of any upper lid procedure, if the eye lid droop is overcorrected.