Diagnostic Ophthalmology

History and clinical signs

An 11year-old, spayed female, American Staffordshire terrier was examined at the ophthalmology service at the Western College of Veterinary Medicine for a red left eye of 1-wk duration. The menace responses, direct and consensual pupillary light reflexes, and palpebral and occulocephalic reflexes were present in both eyes. Schirmer tear test (Schirmer Tear Test Strips; Alcon Canada, Mississauga, Ontario) values were 30 mm/ min in the right and 23 mm/min in the left eye. Fluorescein staining (Fluorets; Bausch & Lomb Canada, Markham, Ontario) was negative bilaterally. The intraocular pressures were estimated with an applanation tonometer (Tonopen XL; Biorad Ophthalmic Division, Santa Clara, California, USA) and were 17 mmHg bilaterally. The pupils were dilated with tropicamide (Mydriacyl; Alcon Canada, Mississauga, Ontario). Biomicroscopic (Osram 64222; Carl Zeiss Canada, Don Mills, Ontario) and indirect ophthalmoscopic (Heine Omega 200; Heine Instruments Canada, Kitchener, Ontario) examinations were completed. Abnormalities noted on direct examination included conjunctival hyperemia, hyphema, and a raised tan-pink mass within the anterior chamber of the left eye. Biomicroscopic examination revealed the mass to be continuous with the iris base from 3 to 7 o’clock, solid, vascularized, and contacting the corneal endothelium. The cornea had mid-stromal vascularization and edema over the region of the mass. Hyphema was confirmed in the anterior chamber and partially obscured the mass. A fibrin clot was present and adherent to the anterior lens capsule. Incipient anterior and posterior cortical cataracts were present bilaterally. No abnormalities were noted in either eye on indirect ophthalmoscopy. A photograph of the left eye is provided for your assessment (Figure 1).

Figure 1.

Photograph of the left eye of an 11-year-old American Stafforshire terrier.

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Discussion

Our clinical diagnosis was an anterior uveal neoplasia and anterior uveitis. The differential diagnoses for an anterior segment mass in the dog include primary neoplasia, such as a ciliary body adenoma or adenocarcinoma, a poorly pigmented melanoma, a hemangioma or hemangiosarcoma, or a leiomyoma; metastic neoplasia, such as lymphoma or adenocarcinoma; and an inflammatory mass, such as a granuloma or a variant form of episcleritis (1,2). A unilateral mass is more suggestive of a primary neoplasm, whereas bilateral disease suggests metastatic disease. Histopathologic examination is required to confirm neoplasia. Methods for obtaining samples to determine the etiology of an intraocular mass include fine needle aspiration of the mass through penetration of a 25 gauge needle at the limbus, intraocular surgery to obtain an incisional or excisional biopsy, and enucleation of the eye for histopathologic examination. In addition to the ophthalmic examination, a complete physical examination, serum biochemical profile, and urinalysis should be completed, and thoracic radiography should be considered to determine if concurrent metastatic disease is present.

Fine needle aspiration is often inadequate for obtaining diagnostic samples in cases of intraocular neoplasia and may precipitate hyphema; therefore, it was not pursued in this case. Incisional biopsy was considered but declined by the owner. Due to the large size of the mass, excisional biopsy was also not an option. Enucleation was chosen as therapy and as a means to obtain a diagnosis. Results from a physical examination, serum biochemical profile, and urinalysis carried out prior to surgery revealed no significant abnormalities. Grossly, the mass measured 2.5 cm × 2 cm. Light microscopic examination confirmed a diagnosis of an adenocarcinoma arising from the ciliary body and base of the iris leaflet.

After uveal melanoma, ciliary body adenoma and adeno-carcinoma are the most common primary intraocular tumors in the dog (3). These tumors arise from the epithelium of the ciliary body and iris, which are of neuroectodermal origin. More common in middle-aged to older dogs, these tumors may be pigmented; however, most are nonpigmented. They most often appear as pedunculated, proliferative lesions in the posterior chamber between the iris and lens and may extend into the ciliary body and base of the iris. These tumors are frequently associated with intraocular hemorrhage, lens luxation or subluxation, anterior uveitis, and anisocoria (3,4). They often incite fibrovascular membrane formation on the surface of the iris called pre-iridal fibrovascular membrane (PIFM), and hyphema is usually a direct result of hemorrhage from the fragile vessels that make up these PIFMs. Glaucoma often results from pupillary blockage or obstruction of the iridocorneal angle due to PIFM formation, or invasion of the iridocorneal angle by tumor cells. Asteroid hyalosis is often seen in affected globes; however, the reason for this is unknown (5).

The differentiation of a ciliary body adenoma from adeno-carcinoma is based on histological characteristics. Adenomas are made up of homogenous cell populations that are well differentiated and organized into sheets or cords with an organized glandular structure, while adenocarcinomas have less obvious glandular organization, cellular pleomorphism, numerous mitotic figures, and a tendency for invasion of adjacent structures (4,5). Despite the histologic classification of adenoma or adenocarcinoma, neither is considered likely to metastasize (5).

Therapy of ciliary body adenoma or adenocarcinoma is similar. Small tumors, extending for less than 3 o’clock hours, may be surgically excised. Surgery should be undertaken only by a veterinary ophthalmologist, as it is complex. Incomplete removal will result in regrowth of the tumor. Larger tumors or eyes that have developed glaucoma, secondary to the tumor, should be treated by enucleation, and the enucleated eye should be submitted for light microscopic examination to confirm the diagnosis.

The prognosis for the eye with ciliary body adenoma or adenocarcinoma is poor, due to progressive intraocular growth and development of uveitis and glaucoma, unless complete excision can be performed. The prognosis for survival, however, is excellent due to the benign behavior of these tumors.