What happens if a mild ptosis is left untreated?

Thank you for your question! While constantly using your forehead to raise your eyebrows will not worsen the ptosis, it could deepen the wrinkles on your forehead. And the natural aging process will make the ptosis worse, irrespective of exertion on your forehead. The reasons for that caused the ptosis will determine the rate at which it progresses. I recommend that you get your condition evaluated and treat it in order to avoid any complications later on. 

Hello, thank you for the excellent question! If left untreated, in most cases ptosis will get worse on its own over time, unrelated to using one's forehead to compensate or lift up the eyelid margin, which is called pseudoptosis. What pseudoptosis will likely cause however is worsening and deepening of forehead wrinkles over time, which is why it is not a good practice to let it go untreated. I recommend scheduling an in person consultation with a board certified plastic surgeon to hear directly from an expert on the options for surgical treatment. Good luck!