Follow-up Question: If I have surgery for ptosis how long does it take to heal? When can I wear my contact lenses?

It varies.  So we can't say for sure but sutures typically are out in 7 days and you will be swollen and possibly bruised for a week.  There is swelling after that that can last weeks to months.  The final result of a ptosis surgery really can't be judged for 6-12 months although usually it should look at least partially corrected within a few weeks.

While it is hard to tell exactly what is going on without seeing your eyes. An in person exam with an oculoplastic surgeon would be best to determine the exact cause of your smaller eye. That being said, there are two main ways to fix ptosis. Either a Levator Advancement or a Mullerectomy. 
In a Levator Advancement, a skin incision is made, the muscle is found and reconnected to the eyelid. The incision is in the lid cease, so it is usually well hidden, and generally not bothersome once it heals. You really only see it when you are closing your eyes and specifically looking for it. In a Mullerectomy, the incision is on the inside of the eyelid, so you don't see it at all. 
Both have their pluses and minuses. 
The healing process is similar in both cases. Everyone always bruises for about 2 weeks and is swollen for 4-6. The entire healing process occurs over a course of the year with the first and biggest milestone being at 6 weeks, when you are 90% healed. 
Generally, contact lenses can be worn after these procedures as long as the patient is careful with the stitches. In Mullerectomy cases, wearing a contact can also work to protect the eyeball from the internal stitch.