What does ptosis refer to in terms of eye condition?

Ptosis refers specifically to the drooping or sagging of the upper eyelid. This condition can affect one or both eyes and may be due to a variety of factors, including muscle weakness, nerve damage, or certain medical conditions. The primary characteristic of ptosis is that it results in the eyelid falling lower than normal, which can obstruct vision or give a tired appearance. Understanding ptosis in this manner is crucial for diagnosing and managing associated conditions, particularly in areas of cosmetic and medical treatment where eyelid position is a key factor in eye health and function.