Keratoconjunctivitis sicca (KCS), more commonly referred to as “dry eye,” is not especially difficult to diagnose. When an owner brings his dog to the veterinarian with a recent history of rubbing and pawing at the face, build-up of crusty or pus-like discharge in the inner pockets of the eyes, swollen or twitching eyelids, excessive squinting and blinking and eye redness, the veterinarian’s initial evaluation will be relatively straightforward. He will take a complete history from the owner, asking about the dog’s health, diet, living environment, travel to other areas, access to other animals and the timing of the onset of the present problems. The owner should be sure to give a thorough background to the veterinarian. Many times, it is helpful for owners to write down a chronology of their dog’s health history before they meet with the veterinarian, including when they first noticed the current symptoms and their frequency.
The veterinarian also will conduct a thorough physical examination, which will include looking into the dog’s eyes through an ophthalmoscope. This is the same hand-held instrument that is used by human doctors when they examine their patients’ eyes. Even though KCS is an ophthalmic disorder, it almost always can be successfully diagnosed and treated by a general veterinary practitioner, without the need to refer the dog to a veterinary eye specialist.
After getting the dog’s history and conducting a physical examination, the veterinarian faced with a dog showing obvious signs of eye discomfort and maybe vision loss will perform a simple, non-invasive, painless test to measure the volume of tears coating and pooling in the patient’s eyes. This is called a “Schirmer Tear Test.” It involves placing the tip of a strip of special filter paper gently into the inner pocket of each of the dog’s eyes, where tears normally pool before they drain or spill out. After one minute, the veterinarian will remove the paper strips and measure how much tear film each strip has absorbed. In a normal dog, the paper will be wet to a distance of at least 15 millimeters (usually about 20 millimeters) after one minute. However, the strips from dogs with dry eye will only absorb tears to a distance of 10 millimeters or less; often, the strips will be wet for less than 5 millimeters.
Another diagnostic tool for dogs suspected of having dry eye is the “Fluorescein Dye Test.” Like the Schirmer Tear Test, this procedure is not painful, invasive or risky. It involves applying drops of fluorescein dye to the surface of the eyes. After a short period of time, the dye will highlight any areas of the cornea that are ulcerated or roughened, both of which often are seen in dogs with dry eye. The attending veterinarian may also want to check the dog’s intraocular pressures, since dogs with dry eye often have abnormal pressure levels inside of their eyeballs. This is a simple test performed with an instrument called a “tonometer,” after applying topical anesthetic eye-drops. More advanced testing is available, but rarely is necessary. In most cases, results of the Schirmer Tear Test are all that is needed to diagnose dry eye.
When a dog shows signs of vision impairment and eye discomfort, it is well worth taking a trip to the veterinarian. If keratoconjunctivitis sicca is the cause of the dog’s distress, it will be diagnosed fairly quickly and usually will be manageable at home with topical drops, ointments or other medications.