The whites of a dog's eyes can be red due to a number of conditions, including an inflammation of the cornea, eyelid, conjunctiva, sclera, ciliary body or iris, according to PetMD. Other possible and more severe causes of red eyes are orbital disease, glaucoma, a hemorrhage at the front of the eye or a hemorrhage within the eye.
Because red eyes in a dog can be a sign of an underlying disease or condition, blood work and other testing is commonly done in a veterinarian's office to rule out or confirm serious diseases, according to PetMD.
PetMD explains that ultrasound eye imaging and tonometry, or the measurement of pressure inside a dog's eye, are two commonly used tests to help diagnose a cause for red eyes. If any pus or discharge is present in the eye, a bacterial culture and sensitivity profile is used to determine if an infection or allergic reaction is occurring.
Most cases of eye redness in dogs can be treated on an outpatient basis, however, in the case of glaucoma, surgery is typically required to repair the eye. A cone collar is commonly used after any treatment on the eyes to prevent a dog from scratching at the eyes and preventing healing, according to PetMD.