There are many things that can cause a canine corneal ulcer. The most common is trauma. For example, from rubbing the eye against an abrasive surface, or from a scratch (while playing with another pet). Another common cause is chemical burn of the cornea, which can happen when shampoo or other irritants get in the eye.
Corneal ulcers can also result from bacterial infections, viral infections, and other diseases. These may either originate in the eye or develop as a result of a disease elsewhere in the body (for example, Epithelial Dystrophy, KCS or "dry eye", diabetes mellitus and others).
A canine corneal ulcer is very painful. Most dogs rub try to relieve the pain by rubbing the eye, which can cause additional damage. Sometimes there is discharge from the eye.
The cornea is a transparent membrane at the front of the eyeball and is made up of three layers. The outermost layer is the epithelium, the center layer is the stroma, and the deepest layer is called the Descemets membrane. Since all of these layers of the cornea are clear, special stains must be applied to view abrasions with an ophthalmoscope.
There are three levels of damage that can occur to the cornea. A corneal abrasion occurs when there is erosion of a few layers of the epithelium. Damage through the epithelium and into the stroma is known as a corneal ulcer. Erosion through the epithelium and stroma to the Descemet's membrane results in a descemetocele.
If the Descemet's membrane ruptures, the fluid inside the eyeball will leak out, the eye will collapse and irreparable damage can occur.
Slight abrasions are usually not visible to the naked eye. An eye stain can be dropped onto the cornea, where it will stain any areas that are ulcerated and can be viewed under special lights. This test is normally used for very superficial abrasions. If the affected area is very deep, cell samples will be taken to review before any stain or medications are applied to the eye.
Treatment depends on the level of damage to the eye.
Corneal abrasions - These usually heal within 3-5 days. Medications including antibiotic drops or ointment will be applied to prevent bacterial infections and relieve pain. The eye should be examined again after 2-3 days of treatment to ensure that it is healing properly.
Canine Corneal Ulcer or Descemetocele - Primary treatment is to protect the eye and promote healing. Surgery may be required to allow the cornea to heal normally. Corneal grafts or surgery to remove dead corneal tissue may also be required. Your veterinarian can advise you of the best course of treatment for your Boston Terrier.