How Can I Fix One Drooping Eye?

Your problem is probably related to a mechanical dysfunction of the eyelid. Perhaps the eyelid muscle has become weaker and needs to be tightened or lifted. This can only be determined by consultation with an eyelid specialist. If this turns out to be the cause of the "drooping" then there are a couple of surgical techniques that may be used to elevated the eyelid. Both procedures usually take under 1/2 hour to perform with minimal bruising and downtime. I hope you find this helpful.

Great question. I would first want to better understand what happened that caused the eyelid to droop. If this was secondary to an infection, there may be underlying scarring or damage to some of the tissues responsible for opening the eyelid. A blepharoplasty can certainly be performed on one side to even things out, but I think it is important to get to the bottom of why this happened. I know many patients who have worn their contacts too long, but I think it is quite rare that they would have long term changes to the eyelid position. Make sure you find a surgeon who is willing to dig to the root cause and not overlook what can potentially be a bigger issue.
Hope this helps,Kyle Kimura, MDFacial Plastic and Reconstructive Surgery

As we age, our eyelids naturally sag and droop. A combination approach would be best to see visible improvement. In terms of non-surgical treatment options, I would recommend a Chemical Brow Lift (using Botox, Dysport, Xeomin, or Jeuveau) and filler injections to rejuvenate the temples, eyebrow, eyelid, eye troughs, upper eye hollows, and forehead. I typically combine this with Ultherapy and thread lifting to lift the brow; RF and skin tightening laser treatments to stimulate collagen production and rejuvenate the skin; and laser or superficial RF devices for improvements in texture, color, and any crepey skin around the eyes as needed. In some cases, surgery is the best solution to achieve the desired results. See an expert for a formal consultation. Best, Dr. Emer.​

There are many reasons for uneven eyelids from uneven excess skin to uneven brow position, but when I hear a patient say my eyes were not always even and then become more uneven after wearing contact lenses, 9 out of 10 times it's because of lid ptosis.
What happens with some contact lens users is that the contact lens rubs against the back surface of the upper eyelids causing inflammation which then causes the eyelid muscle to slip off it's normal attachment. The solution to do a small out-patient surgery repair to correct the lid ptosis. Typically it takes less than 15 min and can be done under local anesthesia. The incision is hidden on the undersurface of the eyelid so there are no visible scars. Stiches come out one week after surgery. It's really quite a quick procedure with minimal pain and minimal downtime.

There are various causes of uneven eyes. The causes can include eyelid, facial, and/or orbit abnormalities, which they in and of themselves could be due to various causes. The treatment would depend on the cause. 
You shouldn't necessarily assume your contact lens history is the cause of your problem, especially because your history doesn't really explain your findings. You should see an Oculoplastic surgeon and Ophthalmologist for a complete evaluation.

Drooping of the upper eyelid itself is known as ptosis. In many cases, upper eyelid asymmetry is related more to brow differences or asymmetries of the surrounding soft tissues than to problems with the lids themselves.
An in-person exam would be needed to give an accurate diagnosis and treatment recommendations.
Best,