Diagnostic Ophthalmology

History and clinical signs

A 6-month-old intact male Boston terrier was examined by the ophthalmology service at the Western College of Veterinary Medicine. This dog was presented for evaluation and repair of a bilateral prolapse of the third eyelid gland. The menace responses, and palpebral, oculocephalic, direct and consensual pupillary light reflexes were normal bilaterally. Schirmer tear test (Schirmer Tear Test Strips; Alcon Canada, Mississauga, Ontario) values were 25 and 31 mm/min in the right and left eyes, respectively. The intraocular pressures were estimated with a rebound tonometer (Tonovet; Tiolat, Helsinki, Finland) and were 16 and 21 mmHg in the right and left eyes, respectively. Fluorescein staining (Fluorets; Bausch & Lomb Canada, Markham, Ontario) of the cornea was negative bilaterally. Retropulsion of both globes was unremarkable. On direct examination including palpation and exteriorization of the third eyelid, a smooth, oval mass involving the bulbar surface of the third eyelid was noted in both eyes. Following application of 0.5% tropicamide (Mydriacyl; Alcon Canada, Mississauga, Ontario), examination of both eyes using a transilluminator (Welch Allyn Finoff Transilluminator; Welch Allyn, Mississauga, Canada) and handheld biomicroscope (Kowa SL-17 Portable Slit Lamp; Kowa, Tokyo, Japan) revealed no other abnormalities. Indirect ophthalmoscopic (Heine Omega 500; Heine Instruments Canada, Kitchener, Ontario) examination was completed and did not reveal abnormalities in either eye. Photographs of this dog at presentation are provided for your assessment (Figure 1).

Figure 1.

Clinical photographs of both (A) and the left (B) eyes at presentation.

What are your clinical diagnoses, differential etiologic diagnoses, therapeutic plan, and prognosis?

Discussion

The ophthalmic diagnosis was prolapsed third eyelid gland in both eyes. Differential diagnoses included third eyelid gland cyst formation, inflammation, and less likely third eyelid neoplasia (1–4).

The third eyelid contains a supportive T-shaped cartilage as well as the gland of the third eyelid, an important contributor to the aqueous tear-film (1). It consists of a bulbar and palpebral surface and is located in the ventromedial fornix (1,2).

Prolapse of the gland of the third eyelid, or “cherry eye,” appears clinically as a protrusion of a red, smooth to follicular, oval mass from the margin of the third eyelid (1,2). This is a common condition and is seen most often in dogs < 2 y old (1,2). The disease can be unilateral or bilateral, and several breeds may be predisposed including cocker spaniels, Boston terriers, shih tzus, English bulldogs, basset hounds, beagles, Lhasa apsos, and Pekingese (1). In a study by Mazzuchelli et al (2), the second gland prolapse was either simultaneous or occurred within 3 mo of the prolapse of the contralateral eye. In this same study, English bulldogs, French bulldogs, cane corsos, shar peis, and great Danes were overrepresented (2). Suspected predisposing risk factors include antigen-stimulated gland enlargement and an abnormality or laxity of the connective tissue attachments between the gland and the periorbital tissues (1,2). Chronic exposure may lead to gland inflammation, enlargement, desiccation, chronic conjunctivitis, and may contribute to keratoconjunctivitis sicca (1,2,5,6).

The mainstay of treatment for a prolapsed third eyelid gland is surgical gland replacement. Historically the gland was removed in its entirety to prevent recurrence; however, this is now discouraged due to the risk of development of keratoconjunctivitis sicca (KCS) following gland excision (1,2). Long-term study has shown that dogs treated with surgical gland replacement have a lower incidence of KCS later in life than dogs that had the gland excised or were untreated (5). There are multiple surgical techniques that can generally be divided into those techniques that anchor the gland (i.e., to the ventral episclera, sclera, insertion of the ventral rectus muscle, base of the third eyelid cartilage, or orbital periosteum), or those that create a pocket for the gland within the conjunctiva on the bulbar surface of the third eyelid (7). Common examples include the Kaswan periosteal anchoring suture and the Morgan pocket technique (5,8).

The Kaswan periosteal anchoring technique involves making a skin incision parallel to the ventromedial orbital rim, then taking a bite of orbital periosteum using 3-0 to 4-0 nonabsorbable monofilament suture. This suture is then tunneled through the subcutaneous tissues and into the dorsal aspect of the third eyelid gland on its medial or lateral side. A horizontal mattress suture is then made, buried within the gland. To accomplish this, the needle is reinserted at each exit point during re-direction, so the suture remains buried below the conjunctiva. The knot is tied securely, and the skin is closed (2,8). The reported success of this procedure ranges from 75 to 100% (2). Because the third eyelid is also anchored, the mobility of this structure is reduced.

The Morgan pocket technique involves creating 2 parallel, elliptical incisions on the posterior surface of the third eyelid, dorsal and ventral to the prolapsed gland. This creates a pocket, into which the gland is reduced as the outer component of these incisions are closed in a simple continuous suture pattern, leaving the ends open to avoid cyst development (5). This technique requires use of magnification and suture choice, and knot placement is important; 6-0 polyglycolic acid or polyglactin 910 are preferred, and the knots must be secured on the anterior surface of the third eyelid to avoid corneal trauma. With the pocket technique, the third eyelid retains its mobility; however, cysts may form if the elliptical incisions are completely closed (7). The reported success of this procedure ranges from 87.5 to 100% (1).

Ultimately, the preferred surgical technique is dependent upon clinician experience and preference as recurrence rates are similar for both techniques. The rates of re-prolapse are reportedly higher in the American bulldog, boxers, and mastiff breeds (2,9). A combined pocket and orbital rim anchorage technique may result in less recurrence in these breeds (9). In addition, a combined technique can be considered for treatment of re-prolapse in any breed.

In this case, the Morgan pocket technique was used. Post-operative therapy included polymyxin B/gramicidin drops (Polysporin; Johnson & Johnson, Guelph, Ontario), q6h in both eyes until recheck examination in 3 wk and eye lubricant (Optixcare; Aventix, Burlington, Ontario), q6h in both eyes for 1 wk. No complications or recurrence were noted to date. A postoperative photograph of this dog is provided for your assessment (Figure 2).

Figure 2.

A 6-month-old Boston terrier immediately following surgical replacement of the gland of the third eyelid using the Morgan pocket technique.

Prolapse of the gland of the third eyelid is a common condition of young dogs of several pre-disposed breeds. Surgical replacement of the gland is the recommended treatment, and although there are several techniques reported, the success rates are similar and generally good. Recurrences may occur, in which case an alternative surgical technique or combination of 2 techniques may be recommended.