Entropion is a inward rolling of the eyelid. It is quite a common congenital defect in sheep and goats, most commonly affecting the lower eyelid. The hairs of the eyelid irritate the corneal surface, causing the eye to run and for staining to appear down the cheek. This is often the first sign which is noted by the keeper.
Luckily, there is a good response to treatment. There are a number of different options for correction: