Sulcus subtarsalis is a groove in the inner surface of eyelid near the eyelid margin and which is also parallel to it.
[1] This separates marginal conjunctiva from tarsal conjunctiva.
It provides space for lodging of foreign bodies.
Arlt's line is a linear line present in the sulcus subtarsalis in Chlamydia trachomatis infection.
[2] This article about the eye is a stub.