Looking Into Their Eyes: Three Basic Veterinary Ophthalmology Screening Tests

Posted on: 29 September 2015


If you bring your dog to the veterinarian because his eyes appear irritated or inflamed, your veterinarian will likely perform three basic tests on your furry friend's eyes. This trinity of standard eye tests can be performed in the examination room within five to ten minutes, and pets tolerate the tests well. Each test is simple to perform, and the results will be helpful in determining a diagnosis and indicating the appropriate course treatment for healing and eyesight preservation.  

Schirmer Tear Test

The Schirmer tear test determines the amount of tear production in each of your dog's eyes. For this test, the bent notch of a small strip of paper is inserted into the lower eyelid. The strip is left in place for 60 seconds. During this time, tears produced by the dog's eye wick their way up the strip of paper, turning the paper from white to blue as the tears make contact. The strip is removed at the one-minute mark, and the level of tear production is assessed. The test strip is marked with escalating numerical values, and the number at which the wicked tears stopped, or the number at which the paper retains its original white color, indicates the tear production value. The test is then performed on the other eye. The Schirmer tear test is used primarily to diagnose keratoconjunctivitis sicca, commonly known as dry eye, but it can also reveal abnormally high tear production that may be resulting from such irritants as an ingrown eyelash or foreign body.

Tonometry Test

The tonometry test is performed to determine the intraocular pressure in your dog's eyes. High intraocular pressure indicates glaucoma, which can be painful and result in a loss of vision. To perform this test, the veterinarian uses a handheld tonometry device, the tip of which is gently applied directly to the corneal surface of your pet's eye and held in place until an intraocular pressure reading is registered. The process is repeated three times on each eye for better accuracy when interpreting the readings.

Fluorescein Dye Test

Once the aforementioned tests have been performed, the final test that your dog will undergo is a fluorescein dye test to evaluate the cornea of each eye. The cornea is the clear, curved membrane that covers the front surface of the eyeball. To administer the fluorescein dye test, the veterinarian will stain the cornea by applying a drop of the dye to the eye. When your dog blinks the dye is distributed over the entire surface of the eye. The eye is then rinsed with an eye wash solution to remove the excess dye, and the examination room's overhead lights are turned off. As the veterinarian shines the light of an ophthalmoscope into your dog's eye, the only visible dye remaining will be that which was taken up by any abnormalities in the corneal surface, such as ulcerations, scratches and other signs of trauma. Corneal ulcers must be treated to prevent irreparable damage to the eye.

Be aware that for a short time after the fluorescein dye test has been performed, your dog's eyes may shed some residual dye, which may stain certain materials. 

Signs That Warrant Eye Examination

Since you cannot present your dog with a reading chart to decipher, you may not notice subtle changes in his visual capacity. There are other signs of eye problems that you can be on the lookout for, including:

  • Squinting
  • Redness
  • Swelling
  • Sensitivity to light
  • A visible third eyelid
  • Excessive tearing
  • Ocular discharge
  • Cloudiness
  • Pawing at the affected eye
  • Rubbing the affected eye on the carpet or other surfaces

These signs may present in one or both eyes, and they warrant an examination with your veterinarian right away. Once the three basic eye tests are performed, a veterinarian (such as one from Murrells Inlet Veterinary Hospital) will either treat the condition diagnosed or, depending on the test results, refer your canine companion to a board certified veterinary ophthalmologist for further evaluation.