Ординатура / Офтальмология / Английские материалы / Slatter's Fundemental of Vetrinary Ophthalmology 4th edition_Maggs, Miller, Ofri_2008

Inferior rectus

FIGURE 17-16. General arrangement of the orbital muscles. (Modified from Prince JH, et al. [1960]: Anatomy and Histology of the Eye and Orbit in Domestic Animals. Charles C. Thomas, Springfield, IL.)

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Exophthalmos frequently causes greater evaporation of the precorneal tear film and exposure keratitis.

Because of the many tissue types present, numerous kinds of neoplasms may affect the orbit. The most common causes of exophthalmos in one case series of dogs and cats were neoplasia (52%), orbital abscesses/cellulitis (30%), hematoma (9%), zygomatic mucocele (5%), arteriovenous fistula (2%), and eosinophilic myositis (2%).

DIAGNOSTIC METHODS

The diagnosis of orbital disorders requires a complete ophthalmic examination and perhaps additional special diagnostic techniques, as follows (Figure 17-19).

•Determination of globe and optic axis displacement helps localize the lesion.

•Orbital palpation. The consistency and position of orbital contents can often be determined by placing pressure on the globe itself, through the eyelids (retropulsion of the globe). Additionally, careful orbital palpation along the rim and inside the orbit with a lubricated fingertip can be useful in localizing lesions.

•Opening of the mouth. Inability to fully open the mouth with enophthalmia is consistent with a restrictive myopathy of the masticatory muscles. If the globe is exophthalmic, substantial pain on opening the mouth suggests an inflammatory process, whereas the absence of pain is more consistent with neoplasia. In dogs and cats the soft tissue posterior to the last upper molar should be carefully inspected and palpated if possible.

•B-scan ultrasonography (see Chapter 5) is very useful for evaluation of soft tissue masses within the orbit and may guide further diagnostic procedures, such as fine-needle aspiration.

•Magnetic resonance imaging (MRI) and computed tomography (CT) (Figures 17-19 through 17-21) yield superior definition in localizing orbital lesions. They allow the extent of disease to be better estimated and enable more accurate surgical planning. CT may be used to guide fineneedle aspiration or biopsy, thus avoiding exploratory orbitotomy.

•Contrast radiographic techniques have been largely supplanted by ultrasound and CT/MRI but may be useful in select cases. The techniques consist of contrast orbital

FIGURE 17-20. Computed tomographic scan of a multilobular ossifying fibroma (sarcoma, chondroma rodens) originating from the right petrous temporal bone and extending rostrally to invade the orbit and nasal cavity, and medially into the middle cerebral fossa, via the frontal, temporal, and parietal bones. The eye was displaced anteriorly. The patient was a 12-year-old Brittany spaniel. (Courtesy Dr. R. Bellhorn.)

FIGURE 17-21. Magnetic resonance image of nasal carcinoma invading the orbit of a dog and causing exophthalmos.

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B

FIGURE 17-22. A, Normal lateral orbital venogram in a 5-year-old poodle (right eye). B, Venogram of left orbit of same dog showing a lymphoid pseudotumor in the inferonasal orbit. The inferior ophthalmic vein is obliterated. (Courtesy Dr. R. Dixon.)

venography (Figure 17-22), contrast orbitography (Figures 17-23 and 17-24), and orbital arteriography (Figures 17-25 and 17-26).

•Fine-needle aspiration or biopsy of orbital contents for cytologic analysis or culture. Guiding these procedures with ultrasound or CT imaging has allowed many orbital lesions to be characterized without resorting to surgical exploration.

•Surgical orbital exploration with or without preservation of the globe

Localization of Foreign Bodies

Depending on the type of foreign body, ultrasonography or radiography can be used to localize a foreign body. For radiography a reference ring of wire may be placed at the limbus (see Figure 17-23); radiographs are taken at four different angles (lateral, ventrodorsal, oblique, frontal) in an attempt to

FIGURE 17-23. Contrast orbitography. Lateral radiograph with the needle in position in the orbital cone after injection of 4 mL of contrast medium. The cone is well filled, with leakage ventrally. A wire marker ring is placed at the limbus. (From Munger RJ, Ackerman N [1978]: Retrobulbar injections in the dog: a comparison of three techniques. J Am Anim Hosp Assoc 14:490.)

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B

FIGURE 17-24. Contrast orbitography. A, Ventrodorsal radiograph of a cat after injection of contrast medium. The cat was blind and exhibited ophthalmoplegia and exophthalmos (orbital fissure syndrome). A filling defect (arrows), present at the left orbital apex, is due to orbital extension of an intracranial lymphosarcoma involving the optic chiasm. B, A lateral oblique view of the skull showing a filling defect (arrows) at the apex of the orbit. (Courtesy Dr. R. Munger.)

differentiate ocular and orbital foreign bodies and determine their location. Nonmetallic foreign bodies tend to be better visualized ultrasonographically. Porcupine quills, which are common orbital foreign bodies in dogs in certain geographic areas, have a characteristic double-banded, linear hyperechoic appearance useful in identifying, localizing, and establishing a prognosis. Wooden slivers, however, are not easily visualized with either technique.

ORBITAL DISEASES

A summary of orbital diseases, classified by type, is given in Table 17-2.

Orbital Cellulitis and Retrobulbar Abscess

Orbital cellulitis and retrobulbar abscess occur most commonly in dogs and cats.

ETIOLOGY. Although retrobulbar abscess is common, its etiology is poorly understood and is not always confirmed. It is assumed to be a bacterial infection, either of hematogenous origin or due to penetrating injury from the oral cavity in association with a foreign body. Mixed flora or no growth is a common finding on aerobic bacterial culture, and in many cases anaerobic culture testing methods are required in order to demonstrate the organisms. Aspergillus spp. and Penicillium spp. have been isolated from orbital cellulitis in cats, and Pasteurella spp. have been isolated from both dogs and cats. The process begins as orbital cellulitis; then localization occurs and an abscess may form. At the stage of cellulitis, the clinical signs are less extreme; that is, pain may be less, oral signs nonexistent, and diagnosis more difficult.

CLINICAL SIGNS. The most important clinical signs of retrobulbar abscess/cellulitis are as follows:

•Exophthalmos (Figure 17-27)

•Periorbital swelling

•Pain on opening the mouth (often extreme)

•Fluctuating red swelling in the oral mucous membrane behind last upper molar (Figure 17-28)

•Protrusion of the third eyelid

•Chemosis, which is usually unilateral

•Pyrexia

•Anorexia

•Leukocytosis

•Acute onset (usual)

DIFFERENTIAL DIAGNOSIS. Retrobulbar abscess must be distinguished from orbital cellulitis (a generalized diffuse inflammation of orbital tissues), which has similar but less marked clinical signs. In orbital cellulitis pain is less evident, pyrexia and anorexia are not as pronounced, and less exudate or no exudate is present on orbital drainage. Orbital cellulitis may progress to retrobulbar abscess. Retrobulbar abscess may be distinguished from other causes of exophthalmos on the basis of its acute onset, pain, and, often, pyrexia. Leukocytosis with neutrophilia may be present.

Clinical signs of retrobulbar abscess are often pathognomonic.

TREATMENT. Orbital cellulitis and retrobulbar abscess are treated similarly, as follows:

1.Drainage via an incision behind the last upper molar (Figure 17-29). A small incision is made through only the oral mucosa. A pair of curved Crile hemostats or a blunt probe (Figure 17-30) is inserted and opened in small steps until the orbit is reached. Orbital tissues should not be crushed or cut during this process so as to avoid damage to the optic nerve or orbital vasculature. This technique allows pockets of exudate to be drained while limiting damage to the orbit. Considerable amounts of exudate under pressure may be released, and dependent drainage to the oral cavity is established. Although exudate is frequently not obtained, drainage is an important prerequisite step in treatment. Failure to locate exudate indicates that the process is still at

O

P L

I

H J

F

E G

A D M K Q N

C B

FIGURE 17-25. Lateral canine orbital arteriogram produced after a retrograde injection of 5 to 10 mL of contrast medium into the infraorbital artery. The arteries of the eye and orbit are outlined. A, Infraorbital artery; B, sphenopalatine artery; C, major palatine artery; D, maxillary artery; E, malar artery; F, anterior deep temporal artery; G, orbital artery; H, ventral muscular branch; I, external ethmoid artery; J, external ophthalmic artery; K, external carotid artery; L, superficial temporal artery; M, posterior deep temporal artery; N, mandibular alveolar artery; O, choroid; P, ciliary body; Q, cannula. (From Ticer JW [1984]: Radiographic Technique in Small Animal Practice. Saunders, Philadelphia.)

D

AC

B

F

G

E

FIGURE 17-26. Canine orbital arteriogram, open-mouth view, produced after a retrograde injection of contrast medium into the infraorbital artery. Displacement, filling defects, and increased vascularity indicate the

F, external ethmoid artery; G, external ophthalmic artery. (From Ticer JW [1984]: Radiographic Technique in Small Animal Practice. Saunders, Philadelphia.)

the cellulitis stage. Ultrasonographic imaging may facilitate draining an orbital abscess.

2.Exudate, if present, is collected for cytologic analysis and possibly aerobic/anaerobic culture.

3.The orbit is gently flushed with sterile saline via the oral incision and the use of a blunt cannula. The wound in the mouth is left open.

4.Systemic antibiotics (e.g., amoxicillin/clavulanic acid, clindamycin, metronidazole) are administered for 7 to 14 days.

5.Soft foods are fed during the recovery period.

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FIGURE 17-27. Retrobulbar abscess in a springer spaniel. A, Frontal view. B, Dorsal view. Note the exophthalmia of the right globe.

Clinical improvement is usually rapid, occurring within 24 hours of treatment. In resistant cases or cases in which a retained foreign body is suspected, exploratory orbitotomy may be necessary.

Cystic Orbital and Periocular Lesions

Orbital and periocular cysts are uncommon. Numerous lesions and tissues may cause cystic swellings, including dacryops (cyst of the lacrimal sac), zygomatic and lacrimal mucoceles in both dogs and cats, retained glandular tissue from the lacrimal or third eyelid gland after enucleation or trauma, sialocele after transplantation of the parotid ducts, and mucocele of the nasal and frontal sinuses, especially in association with neoplasia. Abscesses of the

FIGURE 17-28. A fluctuating swelling caudal to the last upper molar in a dog with a retrobulbar abscess is indicated by arrows.

lacrimal sac and protrusion of orbital fat must be distinguished from cysts because their appearances may be similar.

Frontal Sinus Mucocele

Obstruction of drainage of the frontal sinus into the nasal cavity, combined with creation of an opening from the frontal sinus into the orbit either by trauma, malformation, or other disease processes such as neoplasia, may result in passage of sinus secretions into the orbit via the medial orbital wall. This often results in orbital swelling and orbital pain; if the tract reaches the conjunctiva or periocular skin, there may be a profuse intermittent ocular discharge. The condition often responds temporarily to antibiotic therapy. Diagnosis is made via radiography, CT, or MRI of the frontal sinus, although in select cases a blunt instrument can be passed from the conjunctival fistula into the sinus. It is imperative to rule out frontal sinus neoplasia or fungal infection in patients with mucoceles. Treatment is aimed at establishing drainage from the frontal sinus to the nasal cavity via frontal sinusotomy. Communications between the frontal sinus and the orbit secondary to osteomyelitis may be repaired with a temporalis muscle flap.

FIGURE 17-29. To drain a retrobulbar abscess, an incision approximately 1 cm long (indicated by dotted line) is made through the oral mucosa with a scalpel blade caudal to the last molar.

FIGURE 17-30. A pair of hemostats are inserted in the wound and opened in small steps to establish drainage from the orbit into the oral cavity. (Courtesy Dr. Ellison Bentley.)

Zygomatic Mucocele

A mucocele is caused by leakage of saliva from a gland or duct, with consequent inflammation and fibrous tissue reaction to the saliva. The condition is most commonly seen in dogs, occurring both spontaneously and after head trauma. Zygomatic mucoceles

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are uncommon but must be considered in the differential diagnosis of exophthalmos and space-occupying orbital lesions.

CLINICAL SIGNS. The clinical signs of zygomatic mucocele are as follows:

•Orbital swelling

•Exophthalmos

•Protrusion of the third eyelid

•Protrusion of the oral mucous membrane behind the last upper molar tooth

•Protrusion of a mass beneath the conjunctiva in the inferior temporal or nasal conjunctival fornix

Position of the mucocele within the orbit is variable, with the clinical signs varying accordingly. Aspiration of fluid from within the sac may reveal tenacious, straw-colored, honey-like liquid. Zygomatic mucoceles are usually painless. A zygomatic sialogram may be used to outline the mucocele for planning of surgical removal. Prior to removal, the gland may be outlined by injection of methylene blue up a zygomatic duct.

TREATMENT. Zygomatic mucoceles are best removed by localized orbitotomy depending on the location of the mass, as follows:

1.For masses protruding beneath the conjunctiva behind the lower lid: transconjunctival approach via the inferior conjunctival cul de sac behind the lower eyelid

2.For masses protruding beneath the conjunctiva laterally: an approach posterior to the orbital ligament and dorsal to the zygomatic arch. If necessary the orbital ligament may be transected and resutured.

3.For bulging of the oral mucous membrane, an oral approach behind the last upper molar tooth. If feasible, the mass may be marsupialized into the oral cavity.

Neoplasms and Space-Occupying Lesions

Numerous orbital neoplasms have been described in domestic species, including meningioma, lymphosarcoma, adenocarcinoma, fibrosarcoma, multilobular osteosarcoma, glioma, myxoma, squamous cell carcinoma, rhabdomyosarcoma, and canine lymphoid pseudotumor (Figure 17-31). Retrobulbar neoplasms are uncommon and, in the early stages, present a diagnostic challenge. The most common primary orbital neoplasm in the dog, meningioma is usually a benign solitary neoplasm that grows slowly and produces pressure atrophy. Correct diagnosis is essential to effective treatment.

CLINICAL SIGNS. The clinical signs of orbital neoplasms are as follows:

•Exophthalmos; usually unilateral, slowly progressive, and painless

•Intraconal deviation, displacement, or reduced motility of the globe (see Figure 17-18)

•Periocular swelling

•Prominent or protruding third eyelid

•Blindness in some cases; useful to differentiate from ocular enlargement due to glaucoma, for which blindness is the rule

•Secondary exposure keratitis

•Retinal folds or detachment on ophthalmoscopic examination, due to indentation of the globe by the neoplasm

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B

FIGURE 17-31. A, Transverse computed tomographic scan of a cat with a orbital tumor. The left orbit is “full,” and the globe is deviated anteriorly. B, Reconstructed view of the same image set from above. The retrobulbar mass is clearly visible. (Courtesy University of Wisconsin–Madison Veterinary Ophthalmology Service Collection.)

•Dilated or eccentric pupil

•Papilledema

•Nasal discharge

TREATMENT. Thorough surgical removal is the treatment of choice. In dogs, approximately 90% of orbital tumors are malignant, and complete surgical excision is required. If specialized surgical assistance is available, an exploratory orbitotomy via zygomatic arch resection is recommended. This technique allows exploration and removal of the tumor mass, if possible, with retention of the globe. If the neoplasm is invasive, exenteration of the orbit may be required. In advanced cases with invasion into the bony orbital boundaries, radical orbitectomy may be considered. Orbitotomy allows removal of benign and nonneoplastic lesions (e.g., zygomatic salivary gland mucocele) without loss of the eye. If the lesion is small or well localized by diagnostic procedures, a transconjunctival approach or less radical orbitotomy is useful. Depending on

tumor type, chemotherapy, immunotherapy, and radiation may be combined with surgery to control the neoplastic tissue but are ineffective alone. If radiation therapy is used, the ocular complications must be considered (see Chapter 3).

Multilobular Osteoma

Synonyms: Chondroma rodens, calcifying aponeurotic fibroma. Multilobular osteoma occurs in dogs, cats, and horses, in

which it arises from the flat bones of the skull. Exophthalmos is the most common sign in the orbit. Diagnosis is made by either histopathology or recognition of the radiographic signs (homogenous stippling, evenly undulating well-demarcated borders with a highly radiodense granular appearance). These lesions are generally benign but are occasionally aggressive; a localized multilobular osteoma can be removed surgically. Growth is slow, metastasis is late, and local recurrence can be expected if removal is incomplete. The clinical signs and behavior of multilobular osteoma are similar to those of parosteal osteosarcoma, a rare tumor of the periosteum that has the potential to metastasize, usually later in its course.

Periorbital Fractures

Periorbital contusions and fractures, which occur most commonly in horses, are caused by trauma, uncontrolled or unrestrained behavior, or violent recovery from anesthesia. Diagnosis is more accurate through physical examination performed before and during surgical exploration than with radiography. Clinical signs include pain, crepitus, exophthalmos, periorbital swelling, abrasions, corneal ulceration, uveitis, blepharospasm, ocular entrapment, and facial asymmetry. Fracture of the supraorbital process with extension nasally to the supraorbital foramen and fractures of the lacrimal bone at the nasal canthus may damage the nasal mucosa, causing epistaxis. Bony fragments projecting into the orbit and causing pain, ocular entrapment, and exophthalmos have been observed with fractures near the medial canthus. The nasolacrimal duct may also be damaged.

If fractures are demonstrated on oblique radiographs or on surgical exploration, small pieces of bone may be removed. The conjunctival fornices are palpated, and any bony fragments palpable in the orbit are removed or surgically replaced. Larger fragments may be wired in place, pinned, or treated conservatively by restriction of the horse for 4 to 6 weeks. Early surgical treatment prevents fixation of fragments in abnormal positions by formation of fibrous tissue. Solid synthetic polymers (e.g., silicone or polytetrafluoroethylene [Teflon] sheets) may be inserted and contoured to restore facial profiles for cosmesis. Associated ocular injuries, including corneal ulceration and traumatic uveitis, are common and must be addressed. Contusions and associated edema are treated prophylactically with systemic penicillin/gentamicin and allowed to resolve spontaneously. If necessary, tetanus antiserum should be given.

Early surgical intervention in equine periorbital fractures yields superior cosmetic results.

Eosinophilic Myositis

Eosinophilic myositis occurs most commonly in German shepherds and Weimaraners but is a rare disorder. It usually can

be differentiated from orbital neoplasia, orbital cellulitis, and retrobulbar abscess because it is bilateral.

The clinical signs of eosinophilic myositis are as follows:

•Typically bilaterally symmetrical swelling of masseter, temporal, and pterygoid muscles

•Exophthalmos (variable in extent)

•Chemosis/eyelid edema

•Protrusion of the third eyelid

•Pain on opening the jaws fully

Some animals die during acute attacks; in others the disease resolves, but recurrences are common. Attacks may last 10 to 21 days. Eosinophilia is not a constant sign. The disease may be diagnosed from clinical signs, electromyography, and temporal muscle biopsy. The etiology of eosinophilic myositis is unknown. High doses of systemic steroids and azathioprine have been recommended for treatment. After recovery, temporal and masseter muscle atrophy may occur, together with atrophy of orbital fat and enophthalmos. Affected animals often have difficulty opening the mouth as a result of scarring of the muscles of mastication.

Extraocular Muscle Myositis

An uncommon, presumably immune-mediated disorder, myositis of extraocular muscles affects young (usually less than 1 year) dogs of many breeds, but especially golden retrievers. It is characterized by chemosis and bilateral exophthalmia in which the globes are deviated directly along the direction of the orbital axis (Figure 17-32). Occasionally vision loss occurs if massively swollen extraocular muscles compress the optic nerve. Histologic analysis shows that extraocular muscles (with the exception of the retractor bulbi, which is spared) are infiltrated by lymphocytes and histiocytes. Therapy consists of systemic corticosteroids, with the dosage slowly tapered as the condition resolves. Azathioprine is an alternative drug for use in resistant cases. Although in most animals the disease responds rapidly, recurrence is possible.

Orbital Emphysema

Orbital emphysema uncommonly occurs in dogs and cats after trauma to the paranasal sinuses, with leakage of air into the orbit. The air is palpable as crepitus beneath the conjunctiva or periocular skin. Orbital emphysema has been described, in

FIGURE 17-32. Extraocular muscle polymyositis in a mixed breed dog. The two globes are equally exophthalmic and deviated along the orbital axis.

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which the air may have entered the orbit via the nasolacrimal duct during labored respirations after a routine enucleation.

If emphysema is present, a radiographic study of the sinuses is indicated. The animal is started on systemic antibiotics to prevent infection of the orbit via the paranasal sinuses. In reported cases, spontaneous resolution occurred. If the condition occurs after enucleation, the nasolacrimal duct may be ligated at its orbital exit.

Proptosis of the Globe

Proptosis constitutes an ocular emergency, and its treatment and prognosis are discussed in Chapter 19.

OPHTHALMIC MANIFESTATIONS OF

DENTAL DISEASE

Because of the proximity of the roots of the teeth to the orbit, ocular manifestations and complications of dental disease are common and are frequently overlooked. The most common ocular signs are pain and swelling anterior and inferior to the globe secondary to an abscess of the upper fourth premolar in dogs. The globe may be enophthalmic, and the third eyelid may protrude. Additionally, dental disease has been associated with chronic uveitis and conjunctivitis in dogs and cats.

SURGICAL PROCEDURES

The most common orbital procedures are for removal of the whole or part of the globe or orbital contents; they are defined as follows (Figure 17-33):

•Enucleation: Removal of the globe, third eyelid, conjunctiva, and eyelids

•Exenteration: Removal of the globe, orbital contents, and eyelids

•Evisceration: Removal of the intraocular contents, uvea, lens, retina, vitreous, and eyelids

Enucleation

INDICATIONS. Enucleation is performed for the following reasons:

•Intraocular neoplasia

•Severe perforating ocular trauma with disruption and loss of ocular contents. An evisceration with placement of intraocular prosthesis can often be used instead to preserve cosmetic appearance if desired.

•Uncontrollable endophthalmitis or panophthalmitis

•Intractable ocular pain, especially in glaucomatous eyes

•Owner inability or unwillingness to give long-term treatment to a blind eye to keep it comfortable

Enucleation is an admission that therapeutic attempts to control a pathologic process have failed. It is not used in lieu of a correct diagnosis or treatment.

After enucleation, an intraorbital prosthesis may be used to give a superior cosmetic result. Enucleation in a young animal results in a slower rate of growth of the orbit and a decrease in the final orbital volume than in the other, normal orbit. This slower rate of growth is due to lack of orbital contents.

Removal of the globe only

A

Removal of the globe and orbital contents

B

Removal of the intraocular contents only

C

FIGURE 17-33. Diagrammatic representations of (A) enucleation, (B) exenteration, and (C) evisceration.

Replacement of orbital volume with prosthetic materials after enucleation in a young animal tends to result in an orbit that more closely approximates normal size. If a prosthesis is placed in the orbit of a young animal, a slightly larger prosthesis is chosen than would be indicated by the size of the contralateral eye, to allow for the stimulating effect of the implant on orbital growth, and for normal orbital growth.

There are numerous variations of enucleation techniques. The lateral subconjunctival and transpalpebral approaches are described here. Preoperative use of oral carprofen 12 to 24 hours before surgery in dogs, and of intramuscular morphine (dogs) or butorphanol (dogs and cats) before anesthetic induction, is recommended. Postoperative analgesia for 2 to 3 days is also advised.

Lateral Subconjunctival Enucleation Technique

The lateral subconjunctival approach to enucleation has the advantage of giving better exposure of the optic nerve and orbital vessels. It is used in dogs and cats. The technique proceeds as follows:

1.A lateral, 1- to 2-cm canthotomy is performed to improve exposure (Figure 17-34, A).

2.The conjunctiva is grasped near the limbus with toothed forceps, and a 360-degree perilimbal incision is made beneath it (Figure 17-34, B).

3.The sclera is separated from the conjunctiva, Tenon’s capsule, and extraocular muscles with curved Metzenbaum or Mayo scissors around to the optic nerve (Figure 17-34, B). The lacrimal gland beneath the orbital ligament is left attached to the globe, if possible.

4.The optic nerve may be severed with scissors or with an electrosurgical unit equipped with a tonsil snare

(Figure 17-34, C). Traction must not be placed on the nerve, nor should it be twisted because twisting or traction may damage the optic and cause blindness in the remaining eye, especially in cats. Traction on the extraocular muscles may result in a reduction in heart rate (oculocardiac reflex), especially in horses and birds. A ligature may be placed around the nerve, encircling the associated short and long posterior ciliary vessels before their entry to the sclera. Often it is unnecessary to ligate the optic nerve in dogs and cats. The globe is removed and placed in fixative.

5.An attempt is made to control arterial and venous hemorrhage from the orbital cone with ligatures. If this is impossible, one or two surgical sponges are placed temporarily (5 minutes) in the orbit (Figure 17-34, D).

6.The third eyelid and gland are carefully removed (Figure 17-34, D).

7.Two to 3 mm of the lid margins are removed from the lateral to the medial canthus (Figure 17-34, E).

8.Conjunctiva and Tenon’s capsule are closed with a

simple continuous suture of 3/0 or 4/0 absorbable material. After the conjunctiva has been almost closed, the

surgical sponges are removed and closure is completed. Closure forms a seal to contain further hemorrhage (Figure 17-34, F).

9.The lid incisions are closed with simple interrupted sutures of 4/0 or 5/0 nylon or polypropylene (Prolene)

(Figure 17-34, F). Postoperative swelling is not unusual (especially if continuing hemorrhage occurs) but resolves within 3 or 4 days. As clots within the orbit break down, bloody fluid may appear at the nostril, via the nasolacrimal duct, on the third to fifth day, and owners should be advised accordingly. Postoperative analgesia with oral carprofen and morphine is advised in dogs; carprofen is not approved for use in cats.

The emotional resistance of owners to enucleation should not be underestimated.

All enucleated globes should be submitted for histopathologic examination to rule out an unsuspected disease process, such as neoplasia (Figure 17-35) or lens capsule rupture.