Overview of Ophthalmic Emergencies in Small Animals

The primary goal in these cases is rapid diagnosis and aggressive treatment to maintain the patient's vision. 

Core Management Principles:

• Systemic Priority: A thorough physical examination is critical; any life-threatening systemic diseases must be addressed before focusing on the ocular emergency.

• Aggressive Intervention: Once stabilized, ocular conditions often require immediate and robust medical or surgical action to prevent permanent damage.

Assessment of Vision Potential

Before treatment, the clinician must determine the potential for vision using specific reflexes and responses:

• Menace Response: Testing for a blink in response to a threatening gesture.

• Dazzle Reflex: Testing for a blink or squint in response to a bright light.

• Pupillary Light Reflexes (PLRs):

  • Evaluating both direct and consensual reflexes.

  • Consensual PLR Utility: Particularly useful for assessing the affected eye when the ocular media (such as the cornea or lens) are opaque, preventing a direct reflex assessment.

• Corneal & Globe Issues:

  • Corneal foreign bodies and lacerations.

  • Ulcerative stromal keratitis.

  • Globe ruptures.

• Intraocular & Vision Disorders:

  • Acute glaucoma (sudden rise in eye pressure).

  • Displacement (luxation) of the lens.

  • Acute vision loss.

  • Retinal issues: Retinal detachment and Sudden Acquired Retinal Degeneration Syndrome (SARDS).

Proptosis is defined as a sudden anterior displacement of the globe, where the eyelids become entrapped behind the equator of the eye. 

Etiology and Pathophysiology

• Primary Cause: Blunt trauma, such as being hit by a car or fights with other animals.

• Mechanism:

  • Blunt trauma displaces the globe from the orbit.

  • Eyelids become trapped behind the globe, preventing its return to a normal position.

  • Secondary Effects: Orbital hemorrhage and swelling push the globe further out, leading to corneoconjunctival drying and ulceration.

Prognosis and Vision Recovery

• Factors Influencing Prognosis:

  • Pupil size and reflexes.

  • Duration of exposure and presence of other orbital/globe damage.

  • Patient breed (brachycephalic breeds are predisposed) and presence of systemic trauma.

• Expected Outcomes:

  • Dogs: Approximately 25% recover vision.

  • Cats: Prognosis for vision is considered grave.

Management and Treatment

• Initial Action: Provide immediate moisture and lubrication to the exposed cornea and conjunctiva.

• Surgical Replacement:

  • Requires general anesthesia.

  • Involves a lateral canthotomy and a complete temporary tarsorrhaphy.

  • Technique: Two or three interrupted horizontal mattress sutures with stents placed at half-thickness of the eyelids.

• Medical Therapy:

  • Systemic: Antimicrobials and corticosteroids.

  • Topical: Antimicrobials and mydriatics (if miosis—constricted pupils—is present).

Post-Operative Care

• Timeline: Sutures and stents are typically removed within 14–21 days.

• Prerequisites: Removal should only occur once swelling has subsided and a brisk blink reflex returns.

• Technique: The most medial sutures can be removed first to allow for examination.

• Warning: Premature removal results in lagophthalmia (inability to close the eyelids) and progressive corneal ulceration.

Potential Complications

Following traumatic proptosis, animals may suffer from:

• Blindness due to optic nerve degeneration.

• Corneal ulceration and keratoconjunctivitis sicca (dry eye).

• Enophthalmia (recession of the eye into the socket).

• Lateral strabismus (eye turning outward) caused by injury to the medial rectus muscle.

The primary goal of repair is to ensure precise apposition of the eyelid margin to prevent long-term notch defects and impaired function. 

Urgency and Objectives

• Timing: Lacerations should be repaired as soon as possible.

• Key Goal: Maintain proper lid function and prevent aesthetic defects (notching).

Postoperative Medical Care

• Antimicrobials: Both topical and systemic antimicrobials are often included in the treatment plan.

• Anti-inflammatories: NSAIDs are administered to manage pain and swelling.

• Suture Removal: Skin sutures are typically removed 7–10 days after the procedure.

Corneal foreign bodies are a common occurrence in domestic animals and represent an emergency that requires careful assessment of depth and involvement of the eye's internal structures.

Composition and nature are : 1) Common Materials: Usually composed of organic material or 2) Other Materials: Sand, metal, and glass are also frequently observed.

Clinical Signs and Presentation

• External Signs: Variable blepharospasm (squinting) and tearing.

• Reflex Uveitis Signs:

  • Aqueous flare and miosis (constricted pupil).

  • Iridal swelling and ocular hypotony (low eye pressure).

  • Possible hypopyon (pus in the anterior chamber).

Identification and Assessment

• Common Locations are 1) Conjunctival surface 2) Posterior third eyelid fornix & 3) On or embedded within the cornea.

• Critical Diagnostic Step is establishing the exact depth of the foreign body within the cornea is imperative before attempting removal.

• Precautionary Principle "If the depth is in doubt, clinicians should assume the object has penetrated into the anterior chamber".

Removal and Surgical Management

• Surface Foreign Bodies: Removed under topical anesthesia using vigorous irrigation or small, serrated ophthalmic forceps.

• Deeply Embedded/Penetrating Foreign Bodies: These require general anesthesia for careful removal from the deep corneal layers or the anterior chamber.

• Wound Repair: The corneal wound is typically apposed using simple interrupted 7-0 to 9-0 absorbable sutures.

Prognosis and Potential Complications

• General Outcome: The prognosis for maintaining vision is usually good.

• Potential Complications:

  • Variable corneal scar formation.

  • Septic endophthalmitis (severe internal infection).

  • Cataract formation and secondary glaucoma.

Corneal lacerations are emergency ocular injuries where a penetrating object has damaged the cornea but is not retained within the eye. 

Etiology and Definition

• Common Cause: Cat claw injuries are a frequent cause of full-thickness lacerations.

• Distinction: Unlike penetrating foreign bodies, the damaging object in a laceration is not retained in the ocular tissue.

Clinical Assessment and Prognosis

• Diagnosis: Clinical signs are similar to those of penetrating intraocular injuries.

• Critical Evaluation: It is essential to assess the lens for concurrent involvement.

• Prognostic Factors: The outcome depends on the size and position of the laceration.

• Poorer Prognosis: Associated with involvement of the lens or sclera, or the presence of an iris prolapse.

Surgical Management

• In Visual Patients:

  • Primary Repair: Apposition of the wound using simple interrupted 7-0 to 9-0 absorbable sutures.

  • Stability: A continuous suture line may be added for extra stability.

  • Additional Support: The repair may be covered with a bulbar conjunctival graft or a partial temporary tarsorrhaphy.

• In Blind Patients (e.g., Retinal Detachment):

  • Enucleation is generally considered.

  • Owners may elect for surgical repair solely for cosmetic purposes.

Postoperative Medical Therapy

Treatment is designed to address reflex anterior uveitis and secondary iridocyclitis.

• Antimicrobials: Both topical and systemic versions are used to prevent infectious keratitis or endophthalmitis.

• Anti-inflammatories: Systemic NSAIDs are administered to manage pain and internal inflammation.

• Topical Mydriatics: Used to dilate the pupil and provide comfort.

Potential Complications

Successful repair may still result in several long-term issues: Dense corneal scarring, Cataract formation with posterior synechiae, Secondary glaucoma, Bacterial keratitis or endophthalmitis, Phthisis bulbi (shrunken, non-functional eye).

Clinical Characterization

• Identification of Infection: Recognized by stromal loss, malacia (melting), or stromal cellular infiltrate.

• Reflex Anterior Uveitis: A common concurrent condition characterized by:

  • Aqueous flare and miosis (constricted pupil).

  • Ocular hypotony (low pressure) and fibrin/hypopyon.

• Vulnerability: Central corneal ulcers are particularly at risk because they require more time for the healing response and vascularization.

Diagnostic Evaluation

• Estimation of Depth: Must be accurately assessed using magnification, focal illumination with a slit lamp biomicroscope, and topical fluorescein.

• Laboratory Testing:

  • Corneal cytology.

  • Aerobic bacterial and fungal cultures with sensitivity to guide antimicrobial choice.

• Seidel Test: Uses fluorescein stain to check for active aqueous humor leakage if a corneal rupture is suspected.

Medical Management

• Interim Therapy: Instituted immediately while awaiting culture results:

  • Topical broad-spectrum antimicrobials and serum (to stop melting).

  • Mydriatics: Topical agents to dilate the pupil and address reflex uveitis.

  • Systemic NSAIDs: For pain and inflammation management.

• Systemic Antimicrobials: Required if the globe has been ruptured.

Surgical Intervention

• Threshold for Referral: Ulcers with at least 50% stromal loss should be assessed by an ophthalmologist for surgical stabilization.

• Grafting Techniques:

  • Conjunctival Grafts: The ulcer is covered with an appropriate bulbar conjunctival graft (e.g., pedicle graft).

  • Biomaterials: Porcine small-intestinal submucosa or experimental amniotic membranes.

• Requirement: Adequate ulcer debridement is essential for the successful adherence of a conjunctival graft.

Postoperative Care and Monitoring

• Treatment Duration: Medications are gradually tapered and administered for 4–8 weeks.

• Monitoring Requirements:

  • Regular recheck appointments to ensure proper healing.

  • Intraocular Pressure (IOP) Monitoring: Crucial in breeds at risk for glaucoma, especially when using topical mydriatics.

Potential Complications

Despite successful surgical intervention, several complications may arise:

• Variable corneal scarring and pigmentation.

• Anterior or posterior synechiae (adhesions).

• Secondary cataract formation.

• Rarely, bacterial endophthalmitis (severe internal infection).

Lens luxation occurs when there is a loss of most or all zonular attachments, causing the crystalline lens to become dislocated from its normal anatomical position. 

Classification and Clinical Signs

• Lens Subluxation: Characterized by the classic "aphakic crescent" sign (an area where the lens is absent within the pupil).

• Anterior Lens Luxation: Frequently associated with:

  • Elevated Intraocular Pressure (IOP), often due to pupillary blockage by vitreous or angle closure.

  • Diffuse corneal edema.

  • Pain: Blepharospasm (squinting) and tearing.

  • Episcleral and conjunctival hyperemia (redness).

• Posterior Lens Luxation: Can cause secondary glaucoma, retinal detachment, and chronic anterior uveitis; requires regular monitoring.

Diagnosis and Vision Assessment

• Vision Potential: Typically assessed using the dazzle reflex and consensual pupillary light reflex (PLR).

• Tonometry: Applanation tonometry should be performed carefully if anterior luxation is present.

Management and Treatment

• Contraindication: Prostaglandin analogs are contraindicated in cases of anterior luxation because intense pupil constriction (miosis) can trap vitreous behind the lens and further increase IOP.

• Surgical Intervention:

  • Visual Eyes: Intracapsular lens extraction should be performed as soon as possible.

  • Blind Eyes: Enucleation is recommended to manage a chronically painful globe.

• Alternative Management: Transpupillary aqueous flow can be reestablished using 1% atropine or 10% phenylephrine to dilate the pupil, while positioning the head to move the lens back into the vitreous chamber.

• Prophylaxis: In dogs with early primary instability or posterior luxation, demecarium bromide every 12 hours can delay the onset of anterior luxation.

Postoperative Care and Prognosis

• Post-Op Medical Care: Includes topical and systemic corticosteroids and antimicrobials, as well as topical antiglaucoma medications.

• Monitoring: IOP must be closely monitored, and additional medications prescribed as necessary.

• Prognosis: Guarded, due to common long-term complications.

• Long-Term Complications: Secondary glaucoma, retinal detachment, and uncontrolled anterior uveitis.

Acute vision loss is a clinical emergency categorized into three broad physiological areas: opaque ocular media, retinal dysfunction, and optic pathway disease. 

Opaque Ocular Media

• Mechanism: Physical obstructions or loss of transparency in the eye prevent light from reaching the retina.

• Common Causes:

  • Diffuse corneal edema.

  • Cataracts.

  • Anterior uveitis and keratitis.

• Impact: These conditions can cause vision loss specifically in the affected eye.

Clinical Evaluation (Neuro-Ophthalmic Examination)

A thorough examination is critical for localizing the cause of the blindness.

• Primary Assessments:

  • Menace response: Tests the functional vision pathway.

  • Dazzle reflex: Evaluates subcortical light perception.

  • Palpebral reflex: Assesses cranial nerve function.

  • Pupillary Light Reflexes (PLRs): Critical for evaluating the health of the retina and the optic nerve.

Internal Ocular Assessment (Fundic Examination)

A fundic exam is necessary to rule out extensive physical damage to the internal structures.

• Retinal Evaluation: Rule out diffuse retinal detachment or progressive retinal degeneration (which must involve large amounts of the retina to cause blindness).

• Optic Nerve Evaluation:

  • Lesions of the optic nerve can lead to complete blindness.

  • Diagnostic Challenge: The optic nerve head may appear perfectly normal during an exam if retrobulbar lesions (lesions behind the eye) are present.

Criteria for Referral

• Indication: If the ocular media are clear and the retina appears normal but the patient is still blind.

• Action: Immediate referral to a veterinary ophthalmologist is recommended for advanced testing.

SARDS is a specific condition in dogs characterized by the acute loss of vision, often occurring over the course of several days. 

Affected Populations (Epidemiology)

• Commonly Affected Breeds: Dachshunds, Miniature Schnauzers, Pugs, and Brittany Spaniels.

• Age and Gender:

  • Typically affects middle-aged to older dogs.

  • Spayed females are statistically overrepresented.

Clinical Presentation

• Systemic Signs: Patients often present with symptoms mimicking endocrine disease, including:

  • Weight gain and lethargy.

  • Polyuria and polydipsia (increased urination and thirst).

  • Polyphagia (increased appetite).

• Initial Ocular Signs:

  • Acute, rapid loss of vision.

  • Widely dilated pupils that are poorly responsive or nonresponsive to light stimuli.

  • A relatively normal-appearing fundus initially.

Chronic Ocular Changes

Within a few months of the initial vision loss, clinical signs of retinal degeneration become visible during a fundic examination:

• Tapetal hyperreflectivity.

• Retinal vascular attenuation (thinning of the blood vessels).

Diagnostic Evaluation

• Color Pupillometry: Used to help screen for the condition; the red pupillary light reflex is absent, while a blue pupillary light reflex remains.

• Electroretinography (ERG):

  • Required for a definitive diagnosis; must be performed by an ophthalmologist.

  • SARDS Result: A "flat-line" electroretinogram is observed.

  • Differential Diagnosis: A normal electroretinogram in a blind dog indicates optic pathway disease, which warrants further testing by a neurologist.

Management

• Treatment: To date, there is no effective treatment reported for SARDS.

Retinal detachment is a significant cause of vision loss (either unilateral or bilateral) in animals. Once detected, immediate medical or surgical treatment is necessary to decrease retinal degeneration and facilitate the restoration of vision. 

Etiology and Contributing Factors

Various factors can predispose an animal to or directly cause retinal detachment:

• Breed Predispositions:

  • Shih Tzus (associated with vitreal syneresis).

  • Collies (associated with Collie eye anomaly).

• Previous Ocular Procedures: It is a known and important postoperative complication of lens or cataract surgery.

• Trauma: Physical injury to the eye in both dogs and cats.

• Systemic Conditions: Systemic hypertension is a major contributing factor.

Types and Management Strategies

Treatment approach depends on the underlying nature of the detachment:

• Exudative Nonrhegmatogenous Detachments:

  • Cause: Inflammatory or hemorrhagic intra- and subretinal exudates.

  • Prognosis: Vision may return if treated, though some retinal degeneration usually occurs.

• Small Holes or Breaks (Ventral Retina):

  • Treatment: Successfully managed with barrier retinopexy.

  • Technique: Uses diode laser photocoagulation of the surrounding normal retina.

• Rhegmatogenous Detachments (Holes and Tears):

  • Repair Method: Utilization of advanced vitreoretinal techniques routine in human medicine.

  • Specific Tools:

    • Intraocular gases and silicone oil.

    • Scleral buckling.

    • Laser or cryoretinopexy.