Herbe's pits are diagnostic of:

CHLAMYDIAL CONJUNCTIVITIS: In established trachoma, there may be superior epithelial keratitis, sub epithelial keratitis, pannus, or superior limbal follicles, and ultimately the pathognomonic cicatricial remains of these follicles, known as Herbe's pits--small depressions covered by epithelium at the limbo corneal junction. The associated pannus is a fibrovascular membrane arising from the limbus, with vascular loops extending onto the cornea. All of the signs of trachoma are more severe in the upper than in the lower conjunctiva and cornea. Ref: Nijm L.M., Garcia-Ferrer F.J., Schwab I.R., Augsburger J.J., Correa Z.M. (2011). Chapter 5. Conjunctiva & Tears. In P. Riordan-Eva, E.T. Cunningham, Jr. (Eds), Vaughan & Asbury's General Ophthalmology, 18e.