Chapter 78: Ocular Emergencies

Web Chapter 78


Ocular Emergencies




Ocular emergencies are common in veterinary practice. To preserve vision and minimize patient discomfort, it is important to diagnose and treat ocular disease rapidly. The most common ocular emergencies are discussed in this chapter.



Proptosis


Proptosis is the anterior displacement of the globe with entrapment of the eyelids posterior to the globe. This condition frequently is caused by blunt trauma. Brachycephalic animals may experience proptosis with application of less force than animals of other skull shapes. Because of their shallow orbits, less severe ocular damage may occur in brachycephalic animals with proptosis. In contrast, dolichocephalic dogs and cats require much greater force to produce proptosis because of the deep-seated position of the globe in the orbit in dogs and greater coverage of the globe by the orbital rim in cats. Dolichocephalic animals frequently experience concurrent facial bone fractures and optic nerve trauma.


The prognosis for vision following proptosis is guarded; however, nonvisual eyes may be salvaged for cosmesis. Evaluation of the globe for rupture (based on overall shape and turgor), intraocular hemorrhage, and extraocular muscle rupture is an important component of the initial assessment and the decision making regarding when a proptosed globe should be replaced. Rupture of the posterior sclera is difficult to detect visually; ocular ultrasonography can be useful for assessing the integrity of the globe when rupture is suspected. Pupil size does not reflect prognosis, but intact direct or indirect pupillary light reflexes may indicate a better prognosis for vision. If any extraocular muscle is ruptured, the prognosis for vision decreases because this indicates that severe trauma has occurred and optic nerve damage is likely. When the globe has been ruptured, two or more extraocular muscles have been avulsed, or significant intraocular hemorrhage (i.e., filling more than 50% of the anterior chamber) is present, the prognosis for vision is grave, and the globe should be enucleated. Otherwise, replacement of the globe should be attempted.


A complete physical examination and assessment of the patient’s fitness for general anesthesia should be performed before replacement of a proptosed globe. Globe replacement should be performed under general anesthesia after the patient’s condition has been stabilized (Web Figure 78-1). First, the eyelids are gently clipped and cleaned. A lubricating gel or ointment should be applied to protect the corneal surface. Using 4-0 nonabsorbable monofilament suture, two to three horizontal mattress sutures are then pre-placed through the eyelids starting 5 to 8 mm distal to the margins. Care should be taken to ensure that the sutures are not full thickness because penetration of the lids through the palpebral conjunctiva leads to corneal ulceration. A lateral canthotomy may aid in replacing the globe. While the sutures are pulled upward to evert the eyelids, gentle pressure is placed on the globe using a scalpel handle or other flat, smooth instrument. Stents may be required to relieve tension on the skin sutures. The medial canthus may be left open to facilitate administration of topical medications.



Postoperative systemic therapy should consist of broad-spectrum antibiotics and antiinflammatory dosages of prednisolone (0.5 to 1 mg/kg/day PO) for 7 to 14 days. Topical therapy should consist of broad-spectrum antibiotic drops (one drop every 6 to 12 hours) and atropine (one drop every 24 to 48 hours). Sutures may need to remain in place for at least 4 to 6 weeks and should be replaced after 2 weeks if they have loosened. All animals should wear an Elizabethan collar for as long as the sutures are in place. Complications following proptosis include blindness, keratoconjunctivitis sicca, keratitis, strabismus, anterior uveitis, glaucoma, phthisis bulbi, and optic neuritis.



Eyelid Laceration


Full-thickness eyelid lacerations require immediate surgical closure to prevent drying of the ocular surface and trauma to the globe. Partial-thickness and older wounds should be closed promptly because second-intention healing can lead to eyelid margin irregularities and subsequent keratitis. For all lacerations, débridement of the eyelid should be minimal, and only the truly devitalized tissue should be removed. If more than one third of the eyelid is missing or requires removal, then reconstructive blepharoplasty is required.


Repair should be performed under general anesthesia. Gentle clipping and surgical preparation should be performed. A two-layer closure is required for full-thickness wounds. Apposition of the eyelid margins should be performed first, using 5-0 or 6-0 absorbable suture (Web Figure 78-2). Meticulous care should be used to realign the eyelid margin properly and tie the knot away from the margin. The remainder of the subcutaneous tissue may be closed with a simple interrupted pattern, but placement of full-thickness sutures that penetrate the palpebral conjunctiva should be avoided. The skin then should be apposed with 5-0 nylon or silk. Home care consists of use of an Elizabethan collar to prevent self-trauma and broad-spectrum topical and systemic antibiotic therapy.




Corneal Ulceration


Corneal ulcers are considered emergencies because of their painful nature and the potential for infection, which may lead to loss of the globe. Clinical signs of ulceration of any depth include blepharospasm, serous or mucoid discharge, miosis, and conjunctival or scleral hyperemia. Diagnosis is made by observation of fluorescein stain retention by the stroma. If an ulcer is present, taking a complete history and performing ophthalmic examination with Schirmer’s tear test are essential to determine the underlying cause (e.g., foreign body, eyelid mass, eyelid or eyelash disorder, keratoconjunctivitis sicca, lagophthalmos, or neurologic deficits).


Ulcerations of the cornea are classified as uncomplicated or complicated. Uncomplicated ulcers involve loss of only the corneal epithelium and should heal completely within 1 week. Treatment of uncomplicated corneal ulcers includes application of topical broad-spectrum antibiotic drops or ointments (every 6 to 8 hours) to prevent infection and topical atropine (typically one dose is sufficient) to reduce pain from ciliary body muscle spasm. The use of topical steroids alone or in combination with antibiotics is contraindicated because they impair the normal healing process and promote stromal melting. Prognosis for complete healing of uncomplicated ulceration is excellent.


Complicated corneal ulcers may be superficial, progressive, or deep. They are characterized by one or more of the following:



If an uncomplicated ulcer does not heal in 7 to 10 days, the reason must be determined. A nonhealing superficial ulcer that has no apparent inciting cause most likely can be identified as a spontaneous chronic corneal epithelial defect, also known as an indolent ulcer. Initial treatment options for indolent ulcers include cotton-tipped applicator débridement, diamond burr débridement, and grid keratotomy under topical anesthesia. Deep ulcers that were not produced by deep trauma likely are infected. These have a melting appearance to the stroma due to the actions of collagenases produced by microorganisms and inflammatory cells. A descemetocele is a very deep ulcer that has reached Descemet’s membrane. A characteristic of descemetoceles is that the base of the ulcerated region does not absorb fluorescein stain.


Referral of patients with complicated ulcers to a veterinary ophthalmologist is recommended. Unless the ulcer appears rapidly melting, an infected ulcer with stromal loss of less than 50% of the corneal thickness may be managed with aggressive topical treatment. Broad-spectrum topical antibiotics should be applied every 1 to 2 hours for at least the first 24 to 48 hours. Because of the possibility of corneal rupture through a deep ulcer, ointments should be avoided. Fungal keratitis in dogs and cats is rare, but topical antifungal agents should be used if fungal hyphae are observed on cytologic examination. Unless corneal neovascularization has reached the ulcer bed, systemic antimicrobial therapy is of little benefit. In addition to antimicrobial therapy, treatment should be instituted to stop stromal melting and alleviate pain. Autologous serum contains endogenous anticollagenases and initially should be applied topically every 1 to 2 hours to help prevent further melting. Topical acetylcysteine also may be used, but the growth factors present in serum are lacking. Analgesia should be provided by topical atropine applied every 6 to 8 hours initially to prevent ciliary body spasm. Frequency then may be decreased to every 12 to 24 hours. Systemic antiinflammatory medications, either corticosteroids at antiinflammatory dosages or nonsteroidal antiinflammatory drugs (NSAIDs), can be used to control inflammation. The use of topical steroids is contraindicated.


Ulcers deeper than 50% of the corneal thickness should be treated initially as described previously, and the patient should be referred immediately to a veterinary ophthalmologist for surgical placement of a conjunctival or amnion graft. If corneal melting can be halted and the eye does not rupture, the prognosis for deep ulceration is fair to good. Scarring of the cornea may result, and the degree of corneal involvement will determine how much vision is compromised.


Third eyelid flaps are not recommended in the treatment of complicated corneal ulcers because they can interfere with topical drug delivery, do not deliver vasculature to the ulcer, and impede evaluation of the healing process. Temporary partial tarsorrhaphy can provide protection and allow for medication and visualization but does not provide vascular or structural support of the ulcer.


Please see Chapter 246 for more information about corneal ulcers.

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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Chapter 78: Ocular Emergencies

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