Diagnostic Ophthalmology

History and clinical signs

A 12-year-old, neutered male dog was referred to the ophthalmology service at the Western College of Veterinary Medicine for evaluation of yellow subconjunctival masses located under the palpebral conjunctiva of the upper right eyelid (Figure 1). The upper left and both lower eyelids had similar yellow subconjunctival masses. The menace responses, and the palpebral, direct and consensual pupillary light, and oculocephalic reflexes were present in both eyes. Schirmer tear test (Schirmer Tear Test Strips; Alcon Canada, Mississauga, Ontario) values were within normal reference ranges in both eyes. The intraocular pressures were estimated with a rebound tonometer (Tonovet; Tiolat Oy, Helsinki, Finland) and were 12 mmHg bilaterally. The pupils were dilated with tropicamide (Mydriacyl; Alcon Canada, Mississauga, Ontario). Biomicroscopic examination (Osram 64222; Carl Zeiss Canada, Don Mills, Ontario) did not reveal any other anterior segment abnormalities. Examination of the posterior segments of both globes with an indirect ophthalmoscope (Heine Omega 200; Heine Instruments Canada, Kitchener, Ontario) also failed to identify any posterior segment abnormalities.

Figure 1.

A 12-year-old mixed breed neutered male dog with a yellow subconjunctival mass under the upper right eyelid. Note the location of the mass and the mild associated conjunctivitis. A mild blepharitis was also present.

What are your diagnoses, differential diagnoses, diagnostic plan, and prognosis?

Our diagnosis was bilateral chalazion and secondary conjunctivitis and mild blepharitis. Chalazia, which are common in older dogs (1,2), have a pathognomonic appearance of focal yellow cyst-like structures that are associated with the tarsal glands. They are common accompaniments of tarsal gland adenomas. In this dog, however, there was no evidence of neoplasia. Chalazia develop when the lipid secretion of the tarsal glands is unable to exit the ducts. This may occur due to neoplastic or inflammatory obstruction of the tarsal gland ducts and changes in the consistency of the tarsal gland secretion. The lack of exit of tarsal gland secretion, and continued production of lipid, results in a swollen tarsal gland and eventually tarsal gland rupture. This induces a granulomatous reaction to the extruded lipid by the subconjunctival tissues. Some of these are associated with a secondary bacterial infection, most commonly Staphylococcus spp.; however, it is not known whether the infection is a primary or secondary event. We believe most are infected secondary to the development of the chalazion, and are not the initiating event. Chalazia induce conjunctivitis and mild blepharitis and they are best treated by conjunctival incisions which allow curettage and drainage. The prognosis for the eye and the eyelids are excellent. Recurrence of a chalazion in the tarsal gland and the development of new chalazia are common.

We advised and completed a routine pre-anesthetic data base [complete blood (cell) count, serum biochemical profile, and urinalysis]. All results were within normal reference ranges and we advised and completed routine general anesthesia, and surgically prepared the conjunctival surfaces with dilute betadine solution. Each affected tarsal gland was stabilized using a chalazion clamp and each chazion was incised and curetted. The incisions were left open to heal by secondary intention. The dog recovered uneventfully from general anesthesia and the eyes were treated with a topical triple antibiotic solution (Optimyxin Plus; Sandoz Canada, Bourcherville, Quebec) 1 drop q6h for 1 wk. No additional chalazia were noted at a 1-year follow-up examination.