Ocular Diseases

Chapter 13 Ocular Diseases


Inflammatory Orbital Diseases

Orbital Cellulitis


Acute orbital cellulitis is managed with systemic broad-spectrum antibiotics. Although penicillin may be effective because Arcanobacterium pyogenes is a likely causative organism, ampicillin may be a better choice. Nonsteroidal antiinflammatory agents (NSAIDs) such as aspirin (240 to 480 grains orally, twice daily) provide analgesia and mild antiinflammatory action. Warm compresses of the orbit are very helpful in reducing orbital and lid swelling, thereby lessening the degree of exophthalmos. Compresses may be applied two or three times daily for 5 minutes if labor is available. Topical antibiotic ointment or lubricant should be applied liberally to the cornea to prevent exposure keratitis. If no ulceration of the cornea has occurred, sterile ocular lubricating ointments or mastitis ointments may be used prophylactically. If exposure ulceration has occurred, the eye should be treated topically several times daily with a broad-spectrum antibiotic ointment to control infection and 1% atropine ointment to provide cycloplegia.

The prognosis for acute orbital cellulitis is good if medical and nursing care can be provided. Most cases resolve within 5 to 7 days with the aforementioned therapy.

Chronic orbital cellulitis or abscessation requires localization of the lesion to allow surgical drainage. Needle aspirates or ultrasound-guided needle aspirates confirm the location of the infection before drainage. Knowledge of the skull and orbit anatomy is helpful in avoiding injury to important structures when attempting to lance an orbital abscess (Figure 13-2). Most abscesses harbor A. pyogenes. Therefore systemic penicillin (22,000 U/kg once daily) should be used for 1 to 2 weeks following surgical drainage of the lesion. Gentle flushing of the abscess cavity should be performed once or twice daily, and warm compresses should be used if exophthalmos is severe enough to raise concern of exposure keratitis. Recurrent orbital abscesses or chronic cellulitis will dictate more intensive diagnostic work, including ultrasonography, radiographs, and culture-sensitivity testing to rule out foreign bodies and resistant organisms.

Inflammation of the Tissues Adjacent to the Orbit


Mild to marked unilateral exophthalmos associated with bony expansion of the ipsilateral frontal or maxillary sinus, depression, mild ocular discharge, and fever constitute the major signs in chronic sinusitis (see Chapter 4). Fever may be transient or intermittent, depending on patency of the frontomaxillary-nasal drainage. When purulent material cannot escape, bony expansion of the sinus and fever are more constant. Purulent material can escape through sinus openings into the nasal cavity and cause unilateral purulent nasal discharge. Chronic infection causes extreme softening of the bones surrounding the sinuses and allows for variation in the appearance of the skull. The caretaker may report that the animal’s skull appears swollen on some days but normal on others.

When orbital swelling is obvious, exophthalmos, lid swelling, and chemosis usually are present. Serous ocular discharge is present initially but may become mucopurulent with time. Affected cattle show signs of “headache,” holding the head extended, with eyelids partially closed. Affected sinuses sound duller than normal on percussion.

A. bovis lesions that impinge or extend into the orbit are obvious bony swellings that eventually ulcerate and form draining tracts.

Sinus or skull tumors that compromise the orbital space lead to exophthalmus, ocular discharge, ipsilateral nasal discharge, and fetid breath. Inspiratory dyspnea is more common with neoplasia than infection, although fever is less common with neoplasia. Postorbital lymphosarcoma is especially common in dairy cattle.


Diagnosis may be obvious following physical examination or may require radiographs, ultrasonography, aspirates for cytology, cultures, or biopsy to confirm specific diseases.

Radiographs are useful to confirm sinusitis, and aspirates for cytology and culture allow appropriate antibiotic selection. Biopsies are essential when presence of neoplasia is suspected. Radiographs are very useful to detect cheek/tooth root abnormalities in chronic maxillary sinusitis patients.


Frontal Sinusitis

Trephining of the skull in at least two areas is necessary to provide adequate drainage and lavage of chronic frontal sinusitis in adult cattle. Trephine holes should be 1.75 to 2.5 cm in diameter and drilled at the cornual area (former area of horn) and 3.75 to 4.50 cm off the skull midline along a transverse line drawn through the caudal bony orbit (see Figures 4-10 and 4-11,A and B). Some references suggest a third opening dorsocaudal to the orbit, but in Dr. Rebhun’s experience, this was associated with complications such as entering the orbit. Calves and heifers do not have an extensive frontal sinus except at the cornual area, and trephining the sinus of heifers less than 15 to 18 months of age may lead to invasion of the calvarium.

Purulent material in the sinus should be cultured such that an appropriate antibiotic may be selected for systemic use. The most common isolates from adult cattle and bulls are A. pyogenes and Pasteurella sp. In extremely chronic cases, fluid pus may be replaced by a pyogranulomatous mass of tissue that fills the sinus. When the sinuses cannot be flushed, these patients have an extremely poor prognosis because they often develop fatal meningitis. Lavage of the sinus should be performed daily to flush away discharges and maintain patent trephine holes. Saline, dilute iodine solutions, and other nonirritating lavage solutions may be used. Analgesics such as aspirin (240 to 480 grains orally twice daily for an adult cow) are indicated to alleviate the pain associated with headache.

Successful treatment usually requires 2 weeks of local therapy, systemic antibiotics, and analgesics.

Neoplastic Disease

The most common orbital tumor in dairy cattle is lymphosarcoma. Tumors may be unilateral or bilateral and cause progressive acquired exophthalmos with exposure keratitis or proptosis (Figure 13-3). Because some Jersey, Ayrshire, and Holsteins cows have relative bilateral exophthalmos (i.e., are “bug-eyed” as a normal appearance), early detection of acquired exophthalmos may be difficult for the average caretaker. Therefore severe exophthalmos and exposure damage to the globe secondary to orbital lymphosarcoma may be reported to be acute by the caretaker. This history implies a higher likelihood of orbital cellulitis than neoplasia. However, thorough physical examination to detect other neoplastic target areas and absence of fever usually allows a proper diagnosis. In fact, even though the retrobulbar lymphoid masses obviously have been present and enlarging for some time before pathologic exophthalmos, the pathology may appear very acute once the degree of exophthalmos prevents the eyelids from completely protecting the central cornea. At this point, exposure damage and desiccation of the central cornea coupled with severe blepharospasm, chemosis, and lid swelling dramatically worsen the appearance of the eye (Figure 13-4). A visual eye with moderate exophthalmos but without exposure keratopathy may change to a blind, proptosed eye with complete corneal desiccation in less than 48 hours.

Diagnosis depends on finding other evidence of lymphosarcoma in the patient. Enlarged lymph nodes, melena, cardiac abnormalities, uterine masses, or neurologic signs also may be present. In some patients, the retrobulbar masses are the signal lesions, and other lesions may be undetectable. In this instance, blood for a CBC and bovine leukemia virus (BLV) agar gel immunodiffusion or enzyme-linked immunosorbent assay test is indicated to add supportive data. Most cattle with clinical lymphosarcoma test positive for BLV. This test is supportive but not conclusive because most BLV-positive cattle never develop tumors. Unlike cases with an orbital abscess, serum globulins and inflammatory markers are often normal in cattle with lymphosarcoma. Aspirates from the retrobulbar region may be helpful in some affected cattle. In questionable cases, the proptosed globe should be enucleated to alleviate the cow’s pain and allow collection of tumor material from the orbit for cytology or histopathology. The lymphoid tumors can be palpated along the periorbita and in the orbital cone in most affected cattle. Although the globe usually is free of tumor, rare cases have had conjunctival, corneal, lid, or scleral involvement.

In confirmed cases, the only indication for treatment would be in extremely valuable cattle that are in the last trimester of pregnancy or candidates for embryo transfer in the near future. Enucleation is palliative to relieve the cow’s pain and reduce the possibility of panophthalmitis and orbital cellulitis. Cattle with confirmed orbital lymphosarcoma usually die within 3 to 6 months as a result of diffuse lymphosarcoma. Therefore further treatment is not warranted. Pregnant cattle with confirmed lymphosarcoma masses seldom live through more than 2 to 3 months of gestation. Those that do live to term tend to deliver small, nonviable calves. Embryo transfer attempts in cows with confirmed lymphosarcoma frequently are unsuccessful because of the cow’s catabolic state.

Squamous cell carcinoma may occur in an orbital location but usually is preceded by lid, conjunctival, or corneal squamous cell carcinoma. Orbital squamous cell carcinomas are locally invasive, tend to metastasize, and have a grave prognosis. Carcinomas of respiratory epithelial origin also have been observed in older dairy cattle (more than 8 years of age). These tumors are slow growing over months to years; cause progressive unilateral exophthalmos, inspiratory stridor, and reduced airflow in the ipsilateral nasal airway; and may cause ipsilateral Horner’s syndrome (see Figures 4-5 and 4-6). Although prognosis is poor, affected cattle may be productive for 1 to 3 years with these slow-growing tumors.

Cattle sent to slaughter with severe ocular or orbital neoplasia are condemned when the eye is destroyed, has draining pus, is obscured by neoplasia, has bony involvement, or is associated with lymph node enlargement or emaciation.


Developmental Diseases of the Globe

Etiology and Signs

Developmental malformations of the globe result in megaglobus or microphthalmos (Figure 13-6). Anophthalmos, absence of all ocular tissue, is seldom an appropriate term because histologic section of orbital tissue in suspected anophthalmos cases almost always produces some evidence of ocular tissue, thus making microphthalmos the proper term. Congenital microphthalmia may be unilateral or bilateral in calves. Physical, toxic, and infectious causes have been suggested but seldom are confirmed to explain all sporadic microphthalmia. In utero infection with bovine virus diarrhea virus (BVDV) during the middle trimester occasionally has resulted in microphthalmia.

Genetic causes of microphthalmia appear common in dairy cattle. In Guernsey and Holstein calves, the defect has been linked with cardiac and tail anomalies. Most commonly these calves have a ventricular septal defect and wry tail, as well as unilateral or bilateral microphthalmia. Tail defects other than wry tail have been observed in some Guernsey and Holstein calves with microphthalmia and/or ventricular septal defect. These include absence of a tail, short tail, absence of some sacral vertebrae in addition to coccygeal vertebrae, and atresia ani coupled with absence of vertebrae (see Figure 13-6). In Guernseys, these malformations are thought to be caused by a recessive trait, but in Holsteins, the exact mode of inheritance is unknown.

Congenital megaglobus results from anterior cleavage abnormalities or multiple congenital anomalies producing glaucoma in utero. Dr. Rebhun observed several calves with anterior cleavage anomalies. The lens placode had not separated from the surface ectoderm during the development of those eyes. Subsequent influx of mesodermal tissue forming the corneal stroma, endothelium, Descemet’s membrane, and iris surrounds the lens. The resulting absence of an anterior chamber causes congenital glaucoma and buphthalmos. All cases to date have been unilateral, and the affected eye is noticeably buphthalmic at birth, with corneal edema, central dense opacity (lens in cornea), and no discernable anterior chamber (Figures 13-7 and 13-8).

Convergent strabismus with or without associated relative exophthalmos has been described as an inherited trait in Jersey and Shorthorn cattle. It also has been observed occasionally in Ayrshires, Holstein, and Brown Swiss cattle (Figure 13-9). Bilateral relative exophthalmos (“bug-eyed cows”) is a condition that has been observed in several dairy breeds and probably is a genetic trait. Exophthalmos in these cows does not progress to a pathologic state or exposure keratitis because the eyelids still cover the cornea adequately. However, pigment migration occurs over the bulbar conjunctiva and peripheral cornea as a result of exposure of the globe to dust, air, or debris in some affected cattle.

Congenital nystagmus has been observed in several breeds and is common in Holsteins. The nystagmus is a rapid pendular nystagmus that is horizontal and constant. It persists throughout the animal’s life and does not seem to interfere significantly with vision. The heritability or mode of inheritance is unknown. The trait also has been observed commonly in a herd of purebred Guernseys.

Acquired Diseases

Acquired megaglobus may follow severe intraocular inflammation of exogenous or endogenous cause. Infectious bovine keratoconjunctivitis (IBK), trauma, and uveitis are the usual causes of anterior synechiae, lens luxation, and adhesions that disturb aqueous outflow, thereby creating glaucoma. Endophthalmitis and panophthalmitis secondary to septic uveitis or ocular perforation may also cause megaglobus. If megaglobus is severe enough to cause exposure keratitis, the affected globe should be enucleated to prevent eventual perforation or panophthalmitis. Adult dairy cattle with severe megaglobus treated by enucleation become comfortable and return to anticipated production within several days (Figure 13-10). Therefore it is important that acquired megaglobus is not diagnosed erroneously as a retrobulbar neoplasia.

Less frequently, megaglobus follows intraocular neoplasia or granulomatous infections of the uveal tract. Squamous cell carcinoma is the most frequent tumor to invade the globe, and tuberculosis must be considered when a granulomatous infection of the globe is diagnosed.

Phthisis bulbi (shrinking of the globe) follows ocular perforations, chronic uveal inflammation, and severe pinkeye complications such as corneal perforation and iris prolapse. If a phthisical globe is sterile and nonpainful, it may be ignored. However, if chronic conjunctivitis, facial dermatitis from discharges, and fly irritation affect the cow’s production, enucleation should be performed.


Inflammatory Diseases

Neoplastic Diseases


Fibropapillomas normally are self-limiting within 4 to 6 months and do not require treatment. Persistent or large fibropapillomas (Figure 13-11) may interfere with eyelid function or cause corneal injury and require surgical treatment via cryosurgery or sharp dissection.

Squamous cell carcinomas tend to be locally invasive and may metastasize in some neglected cases. This tumor requires aggressive early therapy to prevent progression, or the cow will be lost. Many therapeutic options exist for early, small squamous cell carcinoma of the eyelids, whereas enucleation, radical exenteration, or culling may be required for large lid lesions. Recognition of early tumor formation when the mass is less than 2.0 cm in diameter allows consideration of cryosurgery, radiofrequency hyperthermia, radiation (if available), sharp surgery, and immunotherapy. Large lid masses (greater than 5.0 cm in diameter) are less likely to be treated successfully because destruction or removal of this much lid tissue may lead to ocular exposure damage (Figure 13-12). These large tumors also are more likely to invade adjacent adnexal tissue, orbital ligaments, periorbita, and bone of the skull. Tumors at the medial canthus are extremely dangerous because they need to advance only 2.0 cm along the medial orbital ligament before entering the bony orbit.

Treatment options include:

6. Enucleation: Enucleation in the calf or cow uses the transpalpebral approach. The cow is restrained in a chute or stanchion and sedated with xylazine (20 to 40 mg IV) before routine preparation of the orbit. The face is clipped and prepared for surgery. A circumferential infiltration of 2% lidocaine is performed approximately 3.75 to 5.00 cm from the eyelid margins, and 35 ml of 2% lidocaine is deposited in the retrobulbar cone via a 8.75-cm (3.5 in), 18-gauge needle. The orbital area is surgically prepped again and draped with a fenestrated drape that can be clamped to the halter with sharp towel clamps. (It is helpful to tape the ipsilateral ear back before draping.) A circumferential incision 1.5 cm from the eyelid margins is made through the skin but not through the palpebral conjunctiva. The incision is completed to the level of the conjunctiva with scissors, and the lid margins are clamped or sewn together. The lateral ligament of the orbit is severed, and dissection continues around the globe superficial to the conjunctiva. All muscles, the optic nerve, and retrobulbar fat are cut as traction is exerted on the globe nasally. The entire nictitans and lacrimal gland are removed. Meticulous attempts at hemostasis only serve to prolong the procedure. A subcutaneous continuous suture of 2-0 catgut closes the orbit, and nonabsorbable interrupted sutures close the skin. Preoperative and postoperative systemic antibiotics are administered for 5 days in routine cases but may be necessary for a longer period in infected globes. Drains are not used unless the orbital tissues appear infected or contaminated.


Inflammatory Diseases

Etiology and Signs

Moraxella bovis, the cause of IBK (i.e., pinkeye), is the most important bacterial disease of the conjunctiva and cornea in cattle. The organisms and IBK will be discussed in the section on the cornea.

Pasteurella and other bacteria may also cause mucopurulent conjunctivitis in cattle occasionally. Pasteurella conjunctivitis occurs in conjunction with severe Pasteurella pneumonia or septicemia in calves. The organisms are normal inhabitants of the upper respiratory tract in cattle and therefore accessible to the conjunctiva. Neisseria spp. have been isolated from cattle with conjunctivitis and infectious keratitis. Atypical (winter) outbreaks of IBK-like endemics have been blamed on these other bacteria, but overwhelming evidence supports M. bovis as the most likely causative organism. Calves with respiratory infections caused by Histophilus somni may have conjunctivitis, rhinitis, laryngitis, and pneumonia. Cattle affected with bacterial conjunctivitis have a serous or mucopurulent ocular discharge, conjunctival injection, and do not appear to have ocular pain.

Mycoplasma and ureaplasma have been isolated from the eyes of cattle during herd epidemics of conjunctivitis. Affected cattle do not appear ill, but 10% to 50% of the animals have a unilateral or bilateral ocular discharge and conjunctival hyperemia. The ocular discharge is serous initially but becomes mucopurulent after 1 to 4 days. No keratitis is associated with this problem.

Infectious bovine rhinotracheitis (IBR) virus, the herpes virus 1 of cattle, may cause a severe endemic conjunctivitis in nonvaccinated cattle. The conjunctivitis may be the only lesion observed in sick cattle or may occur in conjunction with the typical respiratory form of IBR. The disease has been observed in heifers and adult cattle. Typical lesions include severe conjunctival hyperemia, heavy ocular discharge that converts from serous to mucopurulent over 48 to 72 hours, and the presence of multifocal white plaques in the palpebral conjunctiva (Figure 13-14). The lesions may be unilateral or bilateral and affect 10% to 70% of the herd. The plaque lesions are pathognomonic for IBR. Affected adult cattle have high fever (105.0 to 108.0° F/40.56 to 42.22° C), depression, and decreased milk production. Milking cattle with the conjunctival form of IBR appear ill regardless of whether the respiratory form coexists. Heifers with the conjunctival form of IBR may have fever and mild systemic illness but seldom appear as sick as adult milking cattle. The reason for this difference is not known but may be related to the stress of lactation.

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Apr 26, 2017 | Posted by in GENERAL | Comments Off on Ocular Diseases

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