Erosion of a few layers of the epithelium is called a corneal erosion or corneal abrasion. A corneal ulcer is deeper erosion through the entire epithelium and into the stroma.
With a corneal ulcer, fluid accumulates in the stroma, giving a cloudy appearance to the eye. If the erosion goes through the epithelium and stroma to the deepest level of Descemet's membrane, a descemetocele is formed.
A vet will diagnose a CU with fluorescein, a green staining dye.
Corneal Ulcers are mostly caused by accidental injury, such as foliage poking an eye, however it can also be caused by poor eyelid confirmation, where it rubs against the cornea.
What can we do about this painful condition? Due to the clumsy and boisterous nature of the bloodhound, CU's are often caused by an external injury, such as a thorn, a twig etc. However there is also the possibility of it being caused by entropion, in which case the hound should not enter the gene pool.