|The eyebrows protect the eyes from sweat
There are four muscles of facial expression which are
inserted into the skin of the eyebrows and
The eyebrow is securely fastened along the supraorbital ridge through its attachment to the undersurface of the eyebrow fat pad. As supraorbital ridge is absent in the lateral third of the orbital rim, brow ptosis usually begins laterally.
The main cause of brow ptosis is the result of gravitational pull with age. As explained above, the lateral brow is the most commonly affected. However, medial eyebrow can occur with atrophy of the eyebrow fat.
In brow ptosis, the frontalis muscle is used to elevate
the brows and this results in deep forehead furrows. Nonetheless, lateral
brow ptosis usually persists due to the lack of frontalis fibres laterally.