Diagnostic Ophthalmology

History and clinical signs

A 6-year-old, spayed female poodle cross dog was referred to the ophthalmology service at the Western College of Veterinary Medicine for evaluation of an acutely prolapsed left third eyelid, mild exophthalmos, and conjunctivitis (Figure 1). 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 they were 19 mmHg OD and 30 mmHg OS, respectively. 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 abnormalities. Mild discomfort was noted when the globe was retropulsed and the jaws were opened. Oral fistulae could not be identified, although moderate to severe dental tartar and gingivitis and halitosis were present.

Figure 1.

A 6-year-old spayed female poodle cross dog with a prolapsed left third eyelid and mild exophthalmos. The pupils have been dilated pharmacologically to facilitate the ophthalmic examination.

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

Our diagnoses were bilateral epiphora, trichiasis, and left pro-lapsed third eyelid and mild left exophthalmos. The epihora, trichiasis, and mild prolapse of the third eyelids are common presenting complaints voiced to veterinarians and ophthalmologists by owners of smaller breeds of dogs. These conditions can be independent, but more commonly they are related. The epiphora and trichiasis are often linked to mild ocular surface irritation, which stimulates reflex tear production that exceeds nasolacrimal drainage. The third eyelid moves passively secondary to globe retraction due to contraction of the retractor bulbi muscle or displacement by orbital masses.

Epiphora (tear overflow) also commonly develops secondary to decreased drainage (nasolacrimal compromise), excessive tear production (lacrimation) in animals and occurs secondary to painful often inflammatory ocular conditions including keratitis (ulcerative and non-ulcerative), uveitis, glaucoma, scleritis, orbital diseases, and conjunctivitis. Briefly, these conditions are the sum of all red eye etiologies; therefore, the diagnostic approach for epiohora is dependent on a thorough ophthalmic examination including all ocular diagnostic tests. Third eyelid prolapse also has many diverse etiologies including Horner’s syndrome, orbital disorders, globe retraction due to painful ocular conditions to essentially all the causes of red eye previously mentioned.

So what do the examination findings in this dog exclude and what additional diagnostics are useful considerations or are warranted? Note that the neuro-ophthalmic examination was normal and the lack of miosis and anisocoria and the symmetrical bilateral pupillary dilatation exclude Horner’s syndrome. The lack of enophthalmos also excludes Horner’s sysndrome, and orbital fat or muscular atrophy. The lack of pterygium or connjunctival scars excludes post-inflammatory third eyelid displacement. The lack of left ocular retropulsion and the exophthalmos indicate an orbital mass that is inducing third eyelid prolapse and exophthalmos. The symmetrical normal intraocular pressures exclude uveitis and glaucoma. The symmetrical tear tests exclude lacrimation induced epiphora.

With those thoughts in mind the owner was queried about the development of the epiphora versus the third eyelid prolapse and was questioned about the trichiasis and facial hair clips during the dog’s life. The prolapsed third eyelid had developed recently, while the trichiasis and epiphora had been present throughout life. The epiphora did not vary with routine grooming whether the facial hair was trimmed or not. Careful reexamination of the nasolacrimal puncta with the biomicroscope did not detect any obvious abnormalities externally, although mild bilateral medial ventral entropion and curuncular trichiasis were noted. Neither the caruncular trichiasis nor facial trichiasis was inducing clinically obvious keratitis. The next diagnostic steps that could be considered for the bilateral epiphora were Fluorescein dye passage (Jones test), punctal cannulation, and contrast enhanced nasolacrimal sectional imaging (1). The owner declined further diagnostics as the epiphora was a cosmetic issue that had not changed during the dog’s life.

The lack of left ocular retropulsion, prolapsed third eyelid, and exophthalmos are very important signs that warrant orbital imaging as orbital neoplasms, cysts, and cellulitis/abscess need to be differentiated (2). Sectional imaging was recommended, but it was declined due to financial constraints. Ocular/orbital ultrasonography was completed by the ophthalmologist and revealed orbital swelling. After routine sedation, fine-needle aspirates of focal hyperechoic areas noted on ultrasound produced a cellular aspirate that was examined routinely and noted to be a neutrophil rich exudate. Additional diagnostics were advised (microbial culture/sensitivity, skull radiographs, sectional imaging) and they were declined. The dog was returned to the referring veterinarian for routine skull radiographs, oral antibiotic therapy, and dental cleaning and extractions as required. The referring veterinarian reported that multiple abscessed molar and premolar teeth were noted on radiographic skull images. Multiple teeth were removed, and a dental cleaning was completed. The exophthalmos resolved promptly and did not return as noted by follow-up examinations several months later. These findings support a diagnosis of orbital cellulitis that may have developed secondary to dental disease. The epiphora remained similar to previous examinations.