A challenging case: A dog with ocular masses

First thought to be trauma-related scarring, the lesions in this patient's eye stemmed from a somewhat more surprising cause.


Vital Stats
A middle-aged 48.5-lb (22-kg) spayed female Border collie mix was presented to the Colorado State University Veterinary Teaching Hospital for evaluation of a red, weepy left eye. At presentation, the dog was bright, alert, and active.

History

Three months before presentation, an ophthalmologist had evaluated the dog because of a tissue mass on the temporal conjunctiva of its left eye. The dog also had a laceration of the nictitating membrane, so the ophthalmologist suspected that the mass was scar tissue related to trauma. The ophthalmologist recommended a surgical biopsy, but the owners declined it.

Two months after the evaluation, the left eye exhibited redness and discharge, so the owners had presented the dog to its regular veterinarian. The dog was treated for unilateral conjunctivitis with a topical antibiotic ophthalmic ointment twice daily in the left eye. The redness decreased for a few days, but the eye then became painful and more inflamed. The dog was brought to the Colorado State University Veterinary Teaching Hospital because the owners were vacationing in Colorado when the ocular signs worsened.

Other pertinent history findings included that the dog had been a stray in Mexico before the owners adopted it, so the dog's age and breed were unknown. At that time, the dog had a right coxofemoral luxation that had been repaired soon after. The dog had traveled across the western United States and lived in California. The dog's vaccination status was current, and it was receiving topical flea and tick preventive medication.

Physical and ocular examinations

The results of the physical examination were normal except for the left eye. The conjunctiva and episclera were markedly hyperemic, especially temporally, and moderate chemosis, copious mucoid discharge, and blepharospasm were present. A large (6 mm diameter), immobile subconjunctival mass was present at the lateral limbal area that extended temporally. When digitally palpated, the mass felt mildly fluctuant and did not seem to extend behind the globe; however, our palpation was cursory because the mass was causing considerable pain. Retropulsion of the globe was normal, and opening the dog's mouth elicited no pain. The nictitating membrane had a healed laceration along its margin that manifested as a free flap that began at the temporal portion of the horizontal T-shaped cartilage and extended 3 to 4 mm nasally and 2 mm ventrally. The flap did not appear to be causing any problems and was in a distinct location from the subconjunctival mass. Intraocular pressure was 7 mm Hg in the left eye and 15 mm Hg in the right eye (normal = 15 to 25 mm Hg). The results of the remainder of the ocular examination were normal in both eyes.

Although a biopsy of the mass was highly recommended to the owners, they again elected medical therapy. Cytologic evaluation of a conjunctival scraping showed an infiltrate of neutrophils, lymphocytes (few), and plasma cells. The dog received a topical neomycin-polymyxin B-dexamethasone ointment in the left eye every eight hours and amoxicillin trihydrate-clavulanate potassium (13.5 mg/kg) orally twice daily. The dog's ocular signs improved only slightly with this therapy, so the dog was presented to us again two weeks later.

Additional tests

Because of the continuing inflammation in the left eye, we suspected that the mass was not scar tissue and again recommended further diagnostic tests. Topical proparacaine was given, and a conjunctival scraping was done. The cytologic evaluation revealed numerous degenerated neutrophils and eosinophils but no bacterial or fungal organisms. Because of the cytologic examination results, we suspected an infectious or parasitic process. Other differential diagnoses included immune-mediated and neoplastic diseases and a foreign body (e.g. cat claw). An excisional biopsy was recommended because it could provide a diagnosis and might also be curative, as it could remove the entire lesion. The dog's surgery was scheduled for the next day.