Chapter 7 Surgical procedures for the conjunctiva and the nictitating membrane
Bulbar/palpebral conjunctival biopsy (punch/snip) 160
Surgical repair of conjunctival lacerations 161
Surgical repair of conjunctival defects 162
Adaptations in large animals and special species 162
Surgical treatment for symblepharon 162
Conjunctival grafts/transplantation 163
Substitute materials for conjunctival grafts 174
Adaptations in large animals and special species 174
SURGERIES OF THE NICTITANS 176
Surgical treatment of everted nictitans 176
Surgical treatment for hyperplastic lymphoid follicles 177
Surgical procedures for protrusion of the gland of the nictitating membrane or ‘cherry eye’ 178
Surgical procedures for prominent/protruded nictitans 184
Nictitating membrane flaps 185
Partial/complete excision of the nictitans 187
Anatomy of the nictitans
The gross anatomy of the nictitating membrane is quite similar among mammals. Located in the medial canthus, the nictitating membrane is a roughly triangular-shaped fold of conjunctiva, with the base of the triangle consisting of its free or leading margin (Fig. 7.3). Both anterior (palpebral) and posterior (bulbar) surfaces are confluent with the palpebral and bulbar conjunctival mucosa. Its free margin or border is usually pigmented in animals. When non-pigmented, the nictitans appears more prominent. Within the substance of the nictitating membrane is a hyaline T-shaped cartilage plate, which helps provide rigidity to the structure, assists conformation to the corneal curvature, and prevents disfigurement during movement (Fig. 7.4). The ‘arms’ of the T-shaped cartilage are immediately under its leading margin, and are relatively thin and slender compared to the thicker stem or base. The superficial gland of the nictitating membrane in both dogs and cats surrounds the base of the nictitans cartilage and produces seromucoid tears. Both dogs and cats possess a single nictitans gland, but in some species such as birds, the third eyelid gland may have two divisions. The deeper avian third eyelid gland is referred to as the Harderian gland.
Surgical treatment for symblepharon
After general anesthesia, clipping of the eyelid hair, and surgical preparation of the eyelids, the area is draped for aseptic surgery. The conjunctiva is thoroughly cleaned with sterile saline and all foreign material removed by cotton-tipped applicators. After placement of a wire speculum to retract the eyelids, the conjunctiva adhered to the cornea is removed by superficial lamellar keratectomy. The periphery of the corneal lesion is incised by the Beaver No. 6400 microsurgical blade to the level of the superficial stroma (Fig. 7.8a). After lifting the edge of the incision with thumb forceps with 1 × 2 fine teeth jaws, the adherent conjunctiva is excised from the corneal surface (Fig. 7.8b). If the symblepharon continues into the conjunctiva, the incision is continued and the affected conjunctiva excised (Fig. 7.8c). Once the conjunctiva is freely moveable, its edge is apposed to the limbus with 5-0 to 7-0 simple interrupted absorbable sutures. If a defect remains in the bulbar and/or palpebral conjunctiva, its edges are apposed with 5-0 to 7-0 simple interrupted absorbable sutures. To cover the healing cornea and prevent the development of new adhesions between the cornea and conjunctiva, a plastic methyl methacrylate corneal protector (Crouch corneal protector; Storz, St Louis, MO) may be inserted or amniotic membrane apposed by sutures. A soft corneal contact lens may be used instead of the thicker corneal protector (Fig. 7.8d). If considerable adhesions are present between the bulbar and palpebral conjunctivae, a thin strip of silicone sheeting is fashioned to fill the area and secured in position with 4-0 to 7-0 simple interrupted non-absorbable sutures as well as 5-0 to 7-0 simple mattress sutures placed through the silicone strip and the full-thickness eyelid with the suture knots on the external lid surface (Fig. 7.8e). To retain the corneal contact lens and reduce eyelid movements, a partial temporary tarsorrhaphy is performed with 4-0 to 6-0 simple mattress sutures positioned at one-half thickness of the eyelids (Fig. 7.8f). For details on how to perform the temporary tarsorrhaphy, see Chapter 5. After recovery from general anesthesia, an E-collar is placed on the animal to prevent self-mutilation of the surgical site.
Conjunctival grafts/transplantation
Conjunctival autografts
Conjunctiva to conjunctiva
Conjunctival autografts are performed under general anesthesia and routine surgical preparation of the eyelids and conjunctival surfaces. Conjunctival grafts must be thin and devoid of most of the underlying connective tissues. Most conjunctival grafts are either free-hand island or pedicle types. Pedicle grafts are preferred if sufficient adjacent conjunctiva is available. Mucous membrane grafts should be free of pigmentation. The conjunctival graft site must be carefully prepared, and any necrotic or potentially infected tissues removed. The adjacent bulbar conjunctiva is incised by small tenotomy scissors to produce a pedicle flap to cover the surgical defect (Fig. 7.9a). The thin conjunctival pedicle should be 1–2 mm larger than the graft site to compensate for graft shrinkage. As the scissors undermine and separate the conjunctival mucosa from Tenon’s capsule, the scissors’ tips should be plainly visible when the graft is sufficiently thin. Once fitted to the graft site, the edges of the graft and conjunctival mucosa are carefully apposed to ensure epithelium to epithelium apposition with 5-0 to 7-0 simple interrupted absorbable sutures (Fig. 7.9b). A partial temporary tarsorrhaphy can be used to decrease eyelid trauma, and provide pressure to facilitate apposition of the graft to the underlying Tenon’s capsule.
Conjunctival autografts to cornea
Conjunctival autografts are frequently used in small animal ophthalmology in clinical management of deep corneal ulcers, descemetoceles, and perforated corneal ulcers (Figs 7.10-7.12). Conjunctival autografts consist of either bulbar or palpebral conjunctival mucosa with epithelium and connective tissue (fibroblasts, blood vessels, and lymphatics). These autografts can be transposed and sutured onto the cornea to provide additional support and tissue for a cornea weakened by deep ulceration, descemetocele, or perforation with or without iris prolapse. The transplanted conjunctival autograft provides additional tissues and no risk of host rejection.

Fig. 7.10 Extensive keratomalacia in a young dog. This patient is a candidate for a conjunctival autograft.

Fig. 7.13 (a) Descemetocele in a dog treated by a pedicle conjunctival graft (6 weeks postoperative).
Complete (360°) bulbar conjunctival autograft (Gundersen type)
For the 360° fornix-based conjunctival graft, the dorsal bulbar conjunctiva is elevated by fine teeth thumb forceps and incised by scissors at the limbus (Fig. 7.14a). The bulbar conjunctiva is separated from the underlying Tenon’s capsule by alternating blunt–sharp dissection by small tenotomy scissors with blunt tips. For a reasonably thin conjunctival graft, the scissors’ tips should be easily observed through the thin mucosa (Fig. 7.14b). To facilitate dissection, saline can be injected subconjunctivally to help separate the bulbar conjunctiva from Tenon’s capsule. Some hemorrhage is expected and depends on the extent of conjunctival hyperemia associated with the corneal ulceration and secondary iridocyclitis. If the surgical dissection plane enters Tenon’s capsule, additional hemorrhage results.

Fig. 7.14 In the 360°, or Gundersen-type, conjunctival graft,
(d) Once completed, the 360° bulbar conjunctival graft covers the entire cornea.
The edges of the bulbar conjunctiva are apposed horizontally with 5-0 to 7-0 absorbable simple interrupted or simple mattress sutures (Fig. 7.14c). Usually four to six sutures are necessary to appose the dorsal and ventral conjunctival edges. Simple interrupted mattress sutures are recommended if the graft is thicker than desirable or additional traction on the suture line is anticipated. A purse-string stitch has also be used but is not recommended as this produces additional tension on the graft as all edges are pulled to the center of the cornea. Once completed, the 360° bulbar conjunctival graft covers the entire cornea (Fig. 7.14d).
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