Accepted Answer

There are many things that can cause an eye to be red, but the most common are:

Keratoconjunctivitis Sicca (KCS)
Corneal Ulcer
Glaucoma
Bacterial conjunctivitis

Keratoconjunctivitis sicca (KCS) is a fairly common disease in dogs and is also referred to as "dry eye". In this disease, the dog stops producing the watery layer of tears and continues to only produce the oily and mucus layers. With the absence of the aqueous tears, the eyes become dried out, irritated, red, and a build-up of the mucus and oil occurs and cakes around the outside of the eye. Luckily, this disease is easy to diagnose and is very treatable. Since your dog started symptoms in one eye, that has no progressed to the other, I would put KCS very high on the list of possibilities.
You should take your dog into a veterinarian as soon as possible to have this evaluated. The vet can test for KCS using a strip of paper called a Schirmer Tear Test. The vet will also check the eyes for any corneal ulceration or bacterial infection that may have occured secondary to this condition. The treatment involves daily (lifetime) instillation of artificial tears and cyclosporine drops into the affected eyes. Dogs with uncomplicated disease most often make a full recovery as long as treatment is continued.
Corneal ulcers can be a primary problem or a secondary problem to another disease process, and can be tested for with something called a fluoroscein dye test. The vet will instill some green dye into both of the dog's eyes, and then examine them with a purple light. If an ulcer is present it will glow green. Corneal ulcers are treated with topical antibiotics in a preparation designed for the eye as either a drop or an ointment. A topical drug called atropine is also used to control the pain associated with this condition. Corneal ulcers are very commonly seen in dogs secondary to KCS.
Glaucoma and uveitis can both be tested for with an instrument called a Tono-pen or Schiotz tonometer. These will measure the amount of pressure inside the dog's eye. If the dog has glaucoma this can be managed with topical medications until the source of the disease is diagnosed and dealt with. In some cases, this can require surgery.
Bacterial conjunctivitis is diagnosed by ruling all of these other problems out. If the Schirmer Tear Test, Fluorscein dye test and tono-pen exam are all normal, then bacterial conjunctivitis is assumed and is treated for with a topical antibiotic preparation with added steroids for the inflammation and pain. Since your dog has been on antibiotics for this...I think that bacterial conjunctivitis is less likely.
Because your dog has been suffering with this problem since April 23rd..I think that it would be a good idea to try a different veterinarian...or better yet, to ask your vet for a referral to a specialist in veterinary ophtholmology. These specialsits are at referral centers or at colleges of veterinary medicine. The longer your dog goes with these red, irritated, painful eyes...the higher chance that there will be lasting damage to the eyes. Therefore, a quick and accurate diagnosis is of the foremost importance.

I hope that this information is of help to you, and that your dog gets better soon. Please let me know if I can be of further assistance.


Dr. K

Expert:	Dr. K
Pos. Feedback:	99.6 %
Accepts:
Answered:	5/11/2008

Veterinarian

9 years experience as Veterinarian