News & Info

Why are Red eyes an Emergency?

Why am I asked to bring my pet in as an Emergency because of a “Red Eye”?

 Pets can have “red eyes” for many reasons, but several can affect the integrity of the eye if left untreated. It is best to bring your dog or cat in immediately to have it evaluated.

 We may do a few crucial diagnostics tests to determine the cause of the problem:


  1. Physical Examination- A thorough exam of your pet is important to find any other underlying causes, such as bruising or bleeding on other areas of the skin, enlarged lymph nodes, or dental disease.
  2. Ocular Examination- Each part of the eye, including the eyelids, cornea (front clear section of the eye), lens, and retina will be checked for redness, cloudiness, and defects.
  3. Schirmer Tear Test- If we are concerned with a condition called “Dry Eye” or Keratoconjunctivitis sicca (KCS), a strip of paper will be placed underneath your dog’s eyelid for 60 seconds. This paper will measure the amount of tears being produced. If this value is low, your dog will be predisposed to corneal irritation and ulcers which can be very painful.

                    - KCS usually needs lifelong lubricants and a medication that stimulates the tear gland.         Secondary corneal ulcers need immediate treatment.

  1. Fluorescein Stain- A yellow dye may be used to coat the cornea or front part of your dog or cat’s eye to look for ulcers or scratches that can cause a red, painful eye. Regardless if your pet has KCS or had a traumatic incident, a corneal ulcer should be treated immediately.

                    - Corneal ulcers can quickly heal within 3-5 days with the appropriate medication; however, if left untreated, the ulcer will penetrate deeper and become more problematic to resolve- sometimes even needing surgery!

  1. Tonopen- If a Tear Test and Fluorescein Stain are normal, your pet’s eye pressure may be checked. A local anesthetic will be used to numb the eye, then a digitized device will be lightly pressed on the surface to determine a pressure. This number will be verified about three times. If the pressure is increased, a condition called glaucoma may be the cause of the red eye.

                    -  Glaucoma means the circulating fluid within the eye cannot drain because of a blockage. It causes a constant headache in people, so we assume the same is occurring in our pets. Glaucoma can be hereditary (primary glaucoma most commonly seen in Cocker Spaniels and Boston Terriers) or caused by other problems such as inflammation, trauma, or lens luxation. If not treated, glaucoma will continue to be painful and eventually lead to loss of vision. 


A “Red Eye” in dogs and cats can also be due to an allergic reaction which is less worrisome to the health of the eye but can also be uncomfortable. If KCS, a corneal ulcer, or glaucoma is to blame, we recommend an immediate examination to preserve your pet’s comfort and vision!