Another short excerpt from al-Ghazali’s charming little treatise on the wonders of creation, al-Hikma fi Makhluqat Allah:
So He made for the eye sight, and among the wonders of the secret of its nature is its perception of things. It is a matter whose secret is inexplicable. It is composed of seven layers: each layer has an attribute and a special function, and if the eye were deprived of one of the layers or if it ceased functioning then sight would be obstructed. And look to the form of the eyelashes which protect it, and what He created in them: rapidity of motion for protecting the eye from what would get in it and harms it- dust and other things. And the eyelids are, through descending, a gate which opens in the time of need, and which close at other times. And for the purpose of the eyelashes for the beautification of the eyes and face, He made its hair in proper proportion, not exceeding to an excess which would harm the eye, and not diminishing to a diminishment which would harm the eye. And He created in its water salt for the breaking up off of what falls into it, and He made the extremities a little lowered from the middles, for the diversion of what falls in the eye to one of the two sides [of the eye]. And He made the eyebrows a beautifier for the face, and a veil for the eyes, and their hair is similar to the eyelashes in the destruction of destructive increases [in hair length].
Abū Ḥāmed Muḥammad ibn Muḥammad Ghazālī (1058-1111), The Wisdom in God’s Creation