Why is my left eye dropping so noticeably low? (photo)

Thank you for your question. Most often, a droopy eyelid happens due to laxity in upper eyelid skin. Infrequently, if could be related to an abnormality in one of the upper eyelid muscles. I suggest that you move forward and consult with a board certified facial plastic surgeon for an in-person examination that will provide you answers and options for improvement.
Best wishes,

You may want to consult a plastic surgeon with craniofacial training who is likely to order a CT of your entire face with the focus on the upper face, to make the right diagnosis. There are a number of conditions that can cause facial asymmetry but most of them are benign and depending on the condition some simple procedure such as lifting your left eyebrow may deliver a significant amount of improvement. Although, aiming for an optimal outcome may require more complex procedures.

I would see your primary care physician to rule out any medical causes and you may need to monitor this for any further progression of disease prior to undergoing any plastic surgery. There is a progressive disease called Romberg which is hemifacial atrophy where one side of the face slowly gets small and changes over time during late adolescence and early adulthood. It tends to burn out by early adulthood. It looks like your entire eye socket is lower on the left than the right. A CT scan would be able to provide more detail of the underlying anatomy. A craniofacial surgery procedure called the orbital box osteotomy can reposition the eye socket to a more symmetrical position. Less invasive procedures include camouflaging the asymmetry with a left endoscopic forehead lift.