This kitten has had these grey corneas since birth. Why?
Its most probably got a corneal endothelial dystrophy where the endothelium is improperly formed or not metabolically active, not pumping water out of the cornea as it should. When the excess water causes the regular collagen fibril spacing to be disrupted, as in this electron micrograph, the cornea turns from transparent to translucent. The other differential would be glaucoma but the intraocular pressure was 15mmHg in both eyes and the cat could see, if a bit cloudily!