The cornea is the outer, clear surface of the eyeball. Any type of damage to this sensitive surface can result in clouding and/or ulcer formation. Corneal problems can be caused by injuries (long toenails of litter mates), foreign objects (dirt, bedding), infections (bacterial, viral), deficient tear production, and congenital abnormalities such as persistent pupillary membranes and dermoids. Persistent pupillary membranes are tiny tissue strands that arise from the iris (colored portion of the eye surrounding the pupil) and adhere to the inner corneal surface. Dermoids are skin-like appendages that grow hair and occur on the surface of the eye. Both conditions can cause corneal clouding. Flat-faced breeds are more susceptible to injuries due to a greater exposure of the eye surface. Most corneal lesions are difficult to see and require a bright light to visualize. Remember – never use hydrocortisone eye ointment if an ulcer is present.