PEER REVIEWED Clinical Approach to the CANINE RED EYE Elizabeth Barfield Laminack, DVM; Kathern Myrna, DVM, MS; and Phillip Anthony Moore, DVM, Diplomate ACVO he acute red eye is a common clinical challenge for tion of the deep episcleral vessels, and is characterized general practitioners. Redness is the hallmark of by straight and immobile episcleral vessels, which run Tocular inflammation; it is a nonspecific sign related 90° to the limbus. Episcleral injection is an external to a number of underlying diseases and degree of redness sign of intraocular disease, such as anterior uveitis and may not reflect the severity of the ocular problem. glaucoma (Figures 3 and 4). Occasionally, episcleral Proper evaluation of the red eye depends on effective injection may occur in diseases of the sclera, such as and efficient diagnosis of the underlying ocular disease in episcleritis or scleritis.1 order to save the eye’s vision and the eye itself.1,2 • Corneal Neovascularization » Superficial: Long, branching corneal vessels; may be SOURCE OF REDNESS seen with superficial ulcerative (Figure 5) or nonul- The conjunctiva has small, fine, tortuous and movable vessels cerative keratitis (Figure 6) that help distinguish conjunctival inflammation from deeper » Focal deep: Straight, nonbranching corneal vessels; inflammation (see Ocular Redness algorithm, page 16). indicates a deep corneal keratitis • Conjunctival hyperemia presents with redness and » 360° deep: Corneal vessels in a 360° pattern around congestion of the conjunctival blood vessels, making the limbus; should arouse concern that glaucoma or them appear more prominent, and is associated with uveitis (Figure 4) is present1,2 extraocular disease, such as conjunctivitis (Figure 1). If • Hyphema or hemorrhage within the eye appears as severe intraocular inflammation is present, conjunctival either a: hyperemia can also occur in conjunction with episcleral » Settled line of dull to bright red in the anterior chamber injection.1 » Diffuse redness filling the entire chamber (Figure 7). • Subconjunctival hemorrhage appears as amorphous Hyphema can result from clotting disorders, severe blunt areas of deep red below the conjunctiva, obscuring the trauma, or uveitis, and can be associated with systemic view of the individual vessels. Subconjunctival hemor- hypertension. rhage occurs in over-restraint, traumatic injury, clot- ting disorders, and strangulation (Figure 2).1 DISEASES & DIAGNOSTICS • Episcleral injection causes redness because of conges- All red eyes must be evaluated for 3 key ocular diseases that may cause vision loss in an eye (Table 1, page 14): 1. Corneal ulceration 2. Glaucoma 1A 1B 3. Uveitis A few basic diagnostic procedures can quickly assess whether these diseases are present; they should be per- formed in the following order for all patients with ocular signs: 1. Schirmer tear test (STT): Aids in diagnosis of condi- tions associated with decreased tear production, such as keratoconjunctivitis sicca (KCS), and should be per- formed before any medications are administered to the ocular surface Figure 1. Ventral palpebral conjunctival hyperemia and 2. Fluorescein stain: Is critical for diagnosis of corneal 1,2 chemosis secondary to allergic conjunctivitis (A); note ulceration small, fine, tortuous vessels and lymphoid vessels (B). 3. Tonometry: Is critical for diagnosis of glaucoma and uveitis1,2 12 Today’s Veterinary Practice May/June 2013 CLINICAL APPROACH TO THE CANINE RED EYE | 2 3 4 Figure 2. Subconjunctival hemorrhage; note diffuse redness with no obvious congestion of bulbar vessels Figure 3. Episcleral injection associated with glaucoma secondary to an anterior luxated lens; note presence of episcler- al vessels 90° to the limbus. Figure 4. 360° perilimbal deep corneal vascularization (arrow); note episcleral injection (straight, nonmoveable, perilim- bal, episcleral vessels approximately 90° to limbus). 5 6 7 Figure 5. Palpebral and bulbar conjunctival hyperemia and chemosis associated with superficial ulcer secondary to an ectopic cilium (arrow). Superficial corneal neovascularization is present in the dorsal cornea; note long and branching corneal blood vessels. Figure 6. Superficial corneal neovascularization and melanosis, in association with adherent and tenacious mucopuru- lent discharge secondary to KCS; note long, branching corneal blood vessels, which confirms their superficial location. Figure 7. Hyphema secondary to anterior uveitis; note diffuse bright red color and clot obscuring the pupil. Once an examination and these diagnostics are com- Diagnosis & Classification pleted, the eye’s condition can be classified as: Once an ulcer has been identified with positive fluorescein • Extraocular (conjunctival or corneal) staining, further classification allows proper therapeutic • Intraocular (glaucoma or uveitis) interventions and prevents catastrophic complications • Ocular manifestation of systemic disease. related to lack of treatment. Corneal ulcers are classified as superficial or deep:1 CORNEAL ULCERS • Superficial corneal ulcer: Has even and superficial Causes of Red Eye fluorescein stain uptake, with no visible loss of stroma,3 Corneal ulcers result in corneal vascularization, which and presence of long, branching vessels over the cornea appears as a “red eye.” (Figure 5). Corneal blood vessels are an indication of chronic dis- • Deep corneal ulcer: Has an irregular surface, with ease and, generally, take 1 to 3 days to proliferate on the loss of corneal stroma, and presence of focal, fine, non- corneal surface. Uncomplicated corneal ulcers typically branching vessels (Figure 8, page 15). heal in 3 to 5 days; ulcers that do not heal in this time Superficial non-healing ulcers: period must be closely evaluated for confounding factors. • Indicated by superficial staining with diffuse borders Underlying disease that can impede healing include: due to stain under running a nonadherent epithelial lip • KCS (low STT values, rapid tear breakup time) that develops secondary to abnormal wound healing. • Adenexal disease (entropion, distichia, ectopic cilia) • Can be associated with KCS (Figure 6), adnexal disease, • Chronic corneal exposure (lagophthalmos, exophthal- chronic corneal exposure, or foreign bodies (Figure 9, mos). page 15).3 They are often associated with other signs of corneal • Others, however, are believed to occur without concur- melanosis (or “pigmentation”). Corneal vascularization rent disease and are, therefore, associated with primary can occur with nonulcerative corneal disease, but this corneal disease and referred to as spontaneous chronic article strictly focuses on ulcerative disease. corneal epithelial defects (SCCEDs).3 Clinical Note: Blepharospasm is seen with most forms Corneal malacia (melting ulcer): of corneal disease but is a common and nonspecific sign • Presents with visible defects in the corneal surface; cor- of pain associated with many ocular diseases. neal malacia4 appears as soft, gelatinous cornea around May/June 2013 Today’s Veterinary Practice 13 | CLINICAL APPROACH TO THE CANINE RED EYE TABLE 1. THREE KEY OCULAR DISEASES THAT MAY CAUSE VISION LOSS DISEASE CAUSE OF RED EYE DIAGNOSTICS TREATMENT Corneal Corneal vascularization • Slit-lamp examination Superficial ulcer: • Fluorescein staining • Treat underlying disease Disease or Superficial corneal lesion: • Cytology • Topical atropine Ulceration Presence of long, branching • Culture & sensitivity • Topical antibiotic vessels over the cornea • Oral NSAID Deep corneal disease: Presence of focal, fine, Superficial nonhealing ulcer: • Treat underlying disease nonbranching vessels • Debridement of ulcer • Grid keratotomy or DBD Glaucoma Episcleral injection • Tonometry Medical: Deep corneal vascularization • Gonioscopic examination • Prostaglandin analogue drops (360° perilimbal pattern) • High-resolution US or US • IV mannitol biomicroscopy • Oral CAIs Primary glaucoma: Usually associated with a narrow or Surgical: closed filtration angle • Laser cyclophotocoagulation & anterior chamber shunts Secondary glaucoma: Often seen with uveitis or • Endoscopic laser cyclophotocoagulation anterior lens luxation • Enucleation or evisceration Anterior Episcleral injection • Tonometry • Topical atropine 1% Uveitis Deep corneal vascularization • Ocular US • Topical prednisolone acetate 1% and (360° perilimbal pattern) NSAIDs Dx of Underlying Disease: • Systemic NSAIDs Hyphema (blood in anterior • CBC & serum biochemistry • Systemic steroids (only if infectious chamber) • Urinalysis causes ruled out) Iris neovascularization • Tick-borne disease titers • Thoracic & abdominal radiographs • Abdominal US CAI = carbonic anhydrase inhibitor; CBC = complete blood count; DBD = diamond burr debridement; IV = intravenous; NSAID = nonste- roidal anti-inflammatory drug; US = ultrasound the edges of the ulcer and in the ulcer bed (Figure 8) is infected, topical drugs do not promote healing; therefore, or stromal loss, both of which are due to activation of patients should be evaluated for underlying ocular disease matrix metalloproteinases. (eg, KCS) and treated accordingly and concurrently. Routine • Infiltration of the corneal stroma with white blood cells corneal cytology is indicated to rule out low-grade infection. (WBCs; visible as creamy or yellow corneal opacity) Clinical Note: Superficial and uncomplicated ulcers often occurs in conjunction with corneal melting or should heal in 3 to 5 days. stromal loss; this infiltration is considered highly sug- gestive of bacterial or fungal