Deep Corneal Ulcer and Descemetocele

Deep corneal ulcer and descemetocele represent a severe, vision-threatening condition of the cornea characterized by loss of corneal stroma extending to or through the deepest layers, with descemetocele specifically denoting exposure of Descemet's membrane. In veterinary ophthalmology, a deep corneal ulcer is defined as a corneal defect involving more than 50% of the corneal stromal thickness, often approaching Descemet's membrane. A descemetocele occurs when the stroma is completely lost, leaving only the thin, elastic Descemet's membrane and endothelium separating the anterior chamber from the external environment. This condition is a surgical emergency due to the high risk of corneal perforation, iris prolapse, and endophthalmitis. The disease is classified based on depth, presence of infection, and etiology, with surgical grading systems (e.g., the modified Hackett-Jackson classification) guiding therapeutic intervention. Deep corneal ulcers and descemetoceles require prompt, aggressive medical and surgical management to preserve globe integrity and vision.

The etiologies of deep corneal ulcers and descemetoceles are multifactorial. Primary causes include traumatic injuries (e.g., corneal lacerations, foreign bodies, chemical burns), infectious keratitis (bacterial, fungal, viral), neurogenic keratopathy (e.g., facial nerve paralysis, trigeminal nerve dysfunction), and exposure keratopathy secondary to exophthalmos, lagophthalmos, or decreased tear production. In dogs, bacterial infections, particularly with Staphylococcus spp., Streptococcus spp., Pseudomonas aeruginosa, and Escherichia coli, are common, often secondary to corneal trauma or keratoconjunctivitis sicca (KCS). Feline herpesvirus-1 (FHV-1) is a leading cause of ulcerative keratitis in cats, which can progress to deep ulceration and descemetocele, especially with secondary bacterial infection. Fungal keratitis (e.g., Aspergillus spp., Candida spp.) is less common but can be devastating. Iatrogenic causes include inappropriate use of corticosteroids, which can exacerbate corneal melting (keratomalacia) due to collagenase activity. Additionally, breed-related conformational abnormalities (e.g., brachycephalic ocular syndrome) predispose to exposure keratitis and traumatic ulceration. Underlying systemic diseases such as diabetes mellitus, hyperadrenocorticism, and immune-mediated conditions can impair corneal healing and increase susceptibility to infection.

Deep corneal ulcers and descemetoceles are common ophthalmic emergencies in small animal practice. Dogs are more frequently affected than cats, with brachycephalic breeds (e.g., Pugs, Boxers, Bulldogs, Shih Tzus) being at highest risk due to their prominent eyes, shallow orbits, and decreased tear film quality. These breeds often have macroblepharon, lagophthalmos, and nasal fold trichiasis, leading to chronic corneal exposure and trauma. In cats, Persian and Himalayan breeds are predisposed due to similar conformational issues. Age distribution is bimodal: young animals (less than 2 years) often present with traumatic ulcers, while older animals (greater than 7 years) may have underlying KCS or endocrine disorders. No sex predilection is consistently reported, though some studies suggest a higher incidence in males due to increased outdoor activity and trauma. Working dogs, such as hunting and herding breeds, are at increased risk for traumatic corneal injuries. The incidence of infectious keratitis varies geographically, with Pseudomonas and Streptococcus being common in humid environments, and fungal keratitis more prevalent in tropical regions. Overall, deep corneal ulcers account for approximately 10-20% of all corneal ulcer cases presented to veterinary referral centers.

The pathophysiology of deep corneal ulcers and descemetoceles involves a cascade of corneal tissue destruction and attempted repair. The cornea is composed of five layers: epithelium, Bowman's layer (present in dogs but not cats), stroma, Descemet's membrane, and endothelium. The stroma constitutes about 90% of corneal thickness and is composed of collagen fibrils, keratocytes, and glycosaminoglycans. Corneal ulceration begins with epithelial loss, exposing the stroma to tear film proteases, bacterial collagenases, and inflammatory cell-derived matrix metalloproteinases (MMPs). These enzymes degrade stromal collagen, leading to progressive thinning. In deep ulcers, the stromal loss exceeds 50%, and if the process continues, Descemet's membrane, which is resistant to enzymatic degradation, becomes exposed, forming a descemetocele. Descemet's membrane is a thin, acellular layer that can herniate forward due to intraocular pressure, appearing as a transparent or black 'bead' in the corneal defect. The endothelium, which lines the posterior surface of Descemet's membrane, is crucial for corneal deturgescence; its damage can lead to corneal edema. If the descemetocele ruptures, the anterior chamber collapses, the iris prolapses, and the eye is at high risk for endophthalmitis and phthisis bulbi. Concurrently, the cornea attempts to heal by epithelial migration, keratocyte proliferation, and collagen deposition, but this process is often overwhelmed by ongoing enzymatic destruction, especially in the presence of infection or excessive tear film proteases.

Predisposing factors for deep corneal ulcers and descemetoceles are numerous and can be categorized as intrinsic and extrinsic. Intrinsic factors include breed-related conformational abnormalities such as brachycephalic ocular syndrome (macroblepharon, lagophthalmos, exophthalmos, nasal fold trichiasis), which lead to chronic corneal exposure and trauma. Decreased tear production (KCS) is a major intrinsic factor, as tears contain antimicrobial proteins and growth factors essential for corneal health; quantitative or qualitative tear film deficiencies impair epithelial healing and increase infection risk. Neurogenic factors, including facial nerve paralysis (VII) and trigeminal nerve dysfunction (V), result in exposure keratopathy and neurotrophic keratitis, respectively. Endocrine disorders such as diabetes mellitus and hyperadrenocorticism can delay wound healing and increase susceptibility to infection. Immune-mediated conditions, such as chronic superficial keratitis (pannus), can cause corneal scarring and ulceration. Extrinsic factors include traumatic injuries (e.g., cat scratches, foreign bodies, blunt trauma), chemical burns (alkali or acid), and iatrogenic causes such as inappropriate use of topical corticosteroids, which inhibit epithelial migration and collagen synthesis while enhancing collagenase activity. Poor husbandry, such as inadequate nutrition (vitamin A or zinc deficiency), and environmental factors like dusty or smoky environments can also predispose to corneal disease. Prior ocular surgery, such as eyelid surgery or cataract extraction, may alter corneal innervation and tear film, increasing ulcer risk.

Clinical signs of deep corneal ulcers and descemetoceles are often severe and rapidly progressive. Patients typically present with blepharospasm (squinting), epiphora (excessive tearing), photophobia, and a variable degree of ocular discharge (serous, mucoid, or purulent). The conjunctiva is often hyperemic and chemotic. On ophthalmic examination, the corneal ulcer is visible as a depressed, opaque area with a loss of corneal transparency. In deep ulcers, the stroma is thinned, and the ulcer bed may appear gray or yellow due to cellular infiltration and edema. A descemetocele appears as a dark, transparent or black 'bead' or 'blister' within the ulcer, often with a clear zone around it, and the cornea may be markedly edematous. The anterior chamber may be shallow if there is corneal perforation, and a positive Seidel test (fluorescein dye leakage) indicates aqueous humor leakage. In cases of perforation, the iris may prolapse through the corneal defect, appearing as a dark brown or pigmented mass. Systemic signs are usually absent unless there is severe pain or secondary infection. Pain is often severe, leading to anorexia, depression, and self-trauma. In cats with FHV-1, there may be concurrent upper respiratory signs, conjunctivitis, and dendritic ulcers. Chronic cases may show corneal vascularization and pigmentation as healing attempts.

Differential diagnoses for deep corneal ulcers and descemetoceles include other corneal and ocular surface diseases. 1) Superficial corneal ulcers: These involve only the epithelium and superficial stroma, are less painful, and heal rapidly with medical therapy; they do not present with a descemetocele. 2) Corneal foreign body: A foreign body embedded in the cornea can cause a focal ulcer and pain; careful examination and removal are diagnostic. 3) Corneal laceration: A full-thickness or partial-thickness tear due to trauma; may be associated with iris prolapse and requires surgical repair. 4) Corneal sequestration (feline): A focal area of corneal necrosis, common in cats, appears as a brown to black plaque; it can be superficial or deep and may require keratectomy. 5) Bullous keratopathy: Corneal edema with epithelial bullae due to endothelial dysfunction; can lead to ulceration but is not typically associated with stromal loss. 6) Chronic superficial keratitis (pannus): A progressive inflammatory condition of the cornea, often in German Shepherds, characterized by pigmentation and vascularization; can cause ulceration but is usually not deep. 7) Eosinophilic keratitis (feline): A proliferative, white to pink corneal lesion with vascularization, often associated with FHV-1; can cause ulceration. 8) Corneal neoplasia (e.g., squamous cell carcinoma, melanoma): Rare, but can present as a corneal mass with ulceration; biopsy is diagnostic. 9) Glaucoma: Can cause corneal edema and ulceration due to bullous keratopathy, but the primary pathology is elevated intraocular pressure. 10) Uveitis: Can cause corneal edema and keratic precipitates, but ulceration is not a primary feature unless secondary to keratitis. Definitive diagnosis of deep corneal ulcer and descemetocele is based on depth of stromal loss and presence of Descemet's membrane exposure, confirmed by slit-lamp biomicroscopy and fluorescein staining (descemetocele does not stain with fluorescein because Descemet's membrane is hydrophobic).

The diagnostic algorithm for deep corneal ulcers and descemetoceles begins with a thorough history and complete ophthalmic examination. 1) Signalment and history: Note breed, age, and any previous ocular disease or trauma. 2) Neuro-ophthalmic examination: Assess menace response, palpebral reflex, and corneal sensation to rule out neurogenic keratopathy. 3) Schirmer tear test (STT) to evaluate tear production; values less than 15 mm/min in dogs or 10 mm/min in cats indicate KCS. 4) Fluorescein staining: Apply fluorescein dye to the cornea; a deep ulcer will stain green, while a descemetocele will not stain (negative staining) because Descemet's membrane is hydrophobic. 5) Slit-lamp biomicroscopy: Examine the cornea in detail to assess ulcer depth, presence of Descemet's membrane, corneal edema, vascularization, and anterior chamber depth. 6) Intraocular pressure (IOP) measurement: Use tonometry to rule out glaucoma or hypotony (which may indicate perforation). 7) Seidel test: Apply fluorescein and observe under cobalt blue light for a green stream of aqueous humor, indicating a full-thickness corneal perforation. 8) Cytology and culture: Collect corneal scrapings from the ulcer margins for cytology (Gram stain, Diff-Quik) and aerobic bacterial culture and sensitivity; fungal culture if fungal elements are seen or suspected. 9) Advanced imaging: In cases of suspected intraocular extension or orbital involvement, ocular ultrasound or CT may be indicated, but this is rare. 10) Systemic work-up: If an underlying systemic disease is suspected (e.g., diabetes mellitus, hyperadrenocorticism), perform baseline bloodwork (CBC, biochemistry, urinalysis) and endocrine testing. The diagnostic algorithm should be rapid and efficient, as delays can lead to corneal perforation.

Laboratory findings in deep corneal ulcers and descemetoceles are primarily focused on identifying infectious agents and assessing systemic health. 1) Corneal cytology: Smears from the ulcer margin may show neutrophils, bacteria (cocci or rods), fungal hyphae, or viral inclusion bodies (in FHV-1). Gram stain can differentiate Gram-positive (e.g., Staphylococcus, Streptococcus) from Gram-negative (e.g., Pseudomonas) bacteria. 2) Aerobic bacterial culture and sensitivity: This is essential for guiding antimicrobial therapy, especially in deep ulcers or those with melting (keratomalacia). Common isolates include Staphylococcus pseudintermedius, Streptococcus canis, Pseudomonas aeruginosa, and Escherichia coli. 3) Fungal culture: If fungal keratitis is suspected (e.g., in cats or in refractory cases), culture on Sabouraud dextrose agar. 4) Complete blood count (CBC): May show leukocytosis with a left shift in cases of severe systemic infection, but is often unremarkable. 5) Serum biochemistry: May reveal hyperglycemia (diabetes mellitus), elevated liver enzymes (hyperadrenocorticism), or hypoalbuminemia (protein-losing enteropathy or nephropathy) that could impair healing. 6) Urinalysis: To rule out urinary tract infection or proteinuria. 7) Coagulation panel (PT/aPTT): Not routinely indicated unless surgery is planned and there is a history of bleeding diathesis. 8) Inflammatory biomarkers (CRP, SAA): May be elevated in severe keratitis but are not specific. 9) FHV-1 testing: In cats, PCR or immunofluorescence on conjunctival or corneal swabs can confirm FHV-1 infection. 10) Tear film evaluation: Tear film breakup time (TBUT) and tear osmolarity can assess qualitative tear film abnormalities. These laboratory tests help tailor medical therapy and identify underlying predispositions.

Imaging plays a limited but important role in the diagnosis and management of deep corneal ulcers and descemetoceles. 1) Ocular ultrasound: This is indicated when the cornea is opaque and the anterior chamber cannot be visualized, to assess for intraocular abnormalities such as lens luxation, retinal detachment, or intraocular foreign bodies. It can also confirm the presence of a shallow anterior chamber or iris prolapse. 2) Computed tomography (CT): CT is rarely needed but may be useful in cases of suspected orbital trauma or foreign body, or to evaluate the extent of corneal perforation and intraocular involvement. High-resolution CT with contrast can delineate corneal thickness and anterior chamber depth. 3) Magnetic resonance imaging (MRI): MRI provides superior soft tissue contrast and may be used to evaluate the optic nerve and brain in cases of suspected retrobulbar extension, but is not routinely indicated. 4) Fluorescein angiography: Not used for corneal ulcers. 5) Confocal microscopy: In vivo confocal microscopy can provide high-resolution images of corneal layers and is useful for diagnosing fungal keratitis, but is not widely available in veterinary practice. 6) Anterior segment optical coherence tomography (AS-OCT): This non-invasive imaging modality can measure corneal thickness and ulcer depth precisely, and is increasingly used in veterinary ophthalmology. It can help differentiate a deep ulcer from a descemetocele and monitor healing. However, these advanced imaging techniques are not essential for diagnosis, which is primarily clinical.

Cytology and histopathology are valuable for diagnosing the underlying cause of deep corneal ulcers and descemetoceles. 1) Corneal cytology: Scrapings from the ulcer bed and margins are obtained with a sterile spatula or cytobrush after topical anesthesia. Smears are stained with Diff-Quik and Gram stain. Cytological findings may include: Neutrophils (indicative of bacterial infection or sterile inflammation), bacteria (intracellular or extracellular, cocci or rods), fungal hyphae (septate or non-septate), and viral inclusion bodies (Cowdry type A intranuclear inclusions in FHV-1). 2) Histopathology: If a corneal biopsy is performed (e.g., during keratectomy or penetrating keratoplasty), histopathological examination can reveal the depth of ulceration, presence of collagenolysis, inflammatory cell infiltration, neovascularization, and fibrosis. Special stains such as Gram, Giemsa, and Periodic acid-Schiff (PAS) can identify bacteria and fungi. In cases of corneal sequestration, histopathology shows necrotic collagen with a brown pigment. 3) Immunohistochemistry: For FHV-1, immunohistochemistry on corneal tissue can confirm viral presence. 4) In cases of suspected neoplasia, histopathology is diagnostic. 5) Cytology of the anterior chamber (aqueous humor) may be performed if there is concern for intraocular infection or neoplasia, but is rarely indicated. Histopathological evaluation of corneal tissue is essential for definitive diagnosis of chronic or atypical ulcers and for guiding surgical planning.

Treatment of deep corneal ulcers and descemetoceles is a surgical emergency and requires a multi-modal approach. Medical therapy is initiated immediately to stabilize the cornea and control infection, but surgical intervention is almost always necessary to prevent perforation and preserve vision. Preoperative stabilization includes: 1) Systemic and topical antibiotics: Broad-spectrum antibiotics are started empirically, then adjusted based on culture and sensitivity. Topical antibiotics (e.g., ciprofloxacin 0.3% or ofloxacin 0.3% every 2-4 hours) are preferred for corneal penetration. Systemic antibiotics (e.g., amoxicillin-clavulanate 13.75 mg/kg PO q12h or doxycycline 5 mg/kg PO q12h) are used if there is a risk of scleral extension or systemic infection. 2) Anticollagenase therapy: To inhibit corneal melting, use autologous serum (contains alpha-2-macroglobulin) topically every 1-2 hours, or EDTA 0.1% (a metalloproteinase inhibitor) topically every 2-4 hours. 3) Atropine 1% topically every 8-12 hours for cycloplegia and pain relief. 4) Pain management: Systemic opioids (e.g., tramadol 2-5 mg/kg PO q8-12h) or NSAIDs (e.g., carprofen 2.2 mg/kg PO q12h) as needed. 5) Treatment of underlying KCS with cyclosporine 0.2% or tacrolimus 0.03% topically q12h. Surgical techniques for deep corneal ulcers and descemetoceles include: 1) Conjunctival pedicle graft: This is the most common surgical procedure for deep ulcers and descemetoceles. A pedicle of bulbar conjunctiva is mobilized and sutured into the corneal defect with 8-0 to 10-0 absorbable suture (e.g., polyglactin 910 or poliglecaprone 25) in a simple interrupted or continuous pattern. The graft provides structural support, blood supply, and fibroblasts to promote healing. 2) Corneal-scleral transposition: A partial-thickness graft of adjacent cornea and sclera is rotated into the defect; useful for large or peripheral ulcers. 3) Amniotic membrane graft: A biological graft that provides a scaffold for epithelialization and has anti-inflammatory and anti-angiogenic properties; can be used alone or in combination with a conjunctival graft. 4) Tarsorrhaphy (temporary or permanent): Partial or complete eyelid closure to protect the cornea and reduce exposure; often used in conjunction with grafting. 5) Keratectomy: Debridement of necrotic tissue and foreign material from the ulcer bed to promote healing. 6) In cases of corneal perforation with iris prolapse, surgical repair involves replacing the iris, suturing the cornea directly (if possible), or using a graft. 7) Penetrating keratoplasty (full-thickness corneal transplant) is rarely performed in veterinary medicine due to graft rejection risks. Postoperative care includes topical antibiotics, atropine, and serum, as well as systemic antibiotics and analgesics. An Elizabethan collar is essential to prevent self-trauma. The graft is monitored for viability, and sutures are removed in 2-3 weeks if non-absorbable. The prognosis is good if surgery is performed promptly and the eye is not already perforated.

The prognosis for deep corneal ulcers and descemetoceles is generally good if treated promptly and appropriately, but it depends on several factors. Short-term prognosis (first 2 weeks) is guarded due to the risk of graft failure, infection, and corneal perforation. Medium-term prognosis (1-3 months) is good for graft incorporation and corneal healing, with vision preservation in most cases. Long-term prognosis (over 3 months) is excellent for vision and globe survival, but corneal scarring and pigmentation may reduce visual acuity. Success rates for conjunctival pedicle grafts are reported to be 80-95% in dogs and cats. Complications include graft dehiscence, infection, corneal sequestration, and glaucoma. Negative prognostic indicators include: 1) Corneal perforation at presentation, 2) Presence of fungal keratitis, 3) Severe keratomalacia, 4) Brachycephalic conformation with persistent exposure, 5) Poor owner compliance with postoperative care, 6) Underlying systemic disease (e.g., diabetes mellitus), 7) Delayed surgical intervention. With appropriate surgical and medical management, the majority of eyes can be saved, and vision is often preserved, though some degree of corneal opacity is expected.

Follow-up care for deep corneal ulcers and descemetoceles is critical for successful outcomes. Immediate postoperative period (first 24-48 hours): Monitor for signs of graft failure, infection, or increased pain. Recheck daily or every other day for the first week. Suture removal: If non-absorbable sutures are used for the conjunctival graft, they are typically removed at 10-14 days postoperatively. Topical medications are continued for several weeks, with a tapering schedule. Serial ophthalmic examinations: Recheck at 1 week, 2 weeks, 4 weeks, 8 weeks, and 12 weeks postoperatively. At each visit, assess corneal vascularization, graft viability, ulcer depth, and presence of fluorescein staining. Fluorescein staining should be negative (no uptake) by 2-3 weeks postoperatively. Activity restriction: Use an Elizabethan collar at all times for at least 2 weeks, and restrict exercise to prevent trauma. Physical therapy: Not applicable, but gentle cleaning of ocular discharge with saline is recommended. Long-term monitoring: For brachycephalic breeds, consider permanent tarsorrhaphy or other surgical procedures to reduce exposure. Monitor for the development of corneal sequestrum, especially in cats. If KCS is present, continue lifelong topical cyclosporine or tacrolimus. Recheck IOP at each visit to rule out glaucoma. If vision is compromised, consider referral to a veterinary ophthalmologist for advanced procedures. Owner education: Emphasize the importance of medication compliance and recognizing signs of pain or recurrence.

Clinical pearls: 1) Always perform a Seidel test in any deep corneal ulcer to rule out perforation; a positive test requires immediate surgical intervention. 2) In a descemetocele, the ulcer does not stain with fluorescein; this is a key diagnostic feature. 3) Use a conjunctival pedicle graft for deep ulcers and descemetoceles; it provides immediate structural support and promotes healing. 4) When harvesting a conjunctival graft, ensure the pedicle is long enough to reach the defect without tension, and preserve the blood supply by avoiding excessive manipulation. 5) Use absorbable sutures (e.g., 8-0 polyglactin) for corneal suturing to avoid suture removal. 6) Administer topical atropine to reduce ciliary spasm and pain, but monitor for decreased tear production. 7) In cats, consider FHV-1 as a cause and use topical antiviral therapy (e.g., cidofovir 0.5% or famciclovir systemically). 8) Autologous serum is a cost-effective anticollagenase; prepare fresh serum and refrigerate. 9) Always treat underlying KCS with cyclosporine or tacrolimus to prevent recurrence. 10) Use a temporary tarsorrhaphy in addition to grafting to protect the cornea during healing. Pitfalls: 1) Do not use corticosteroids in any corneal ulcer, as they exacerbate collagenolysis and delay healing. 2) Avoid using fluorescein in a descemetocele, as it may cause staining of Descemet's membrane and confuse the diagnosis. 3) Do not delay surgery; a descemetocele can rupture spontaneously, leading to iris prolapse and loss of the eye. 4) Do not place sutures through Descemet's membrane, as this can cause aqueous humor leakage. 5) Avoid excessive cautery or debridement of the ulcer bed, which can damage healthy tissue. 6) Do not use topical anesthetics for pain management, as they are toxic to the corneal epithelium. 7) Ensure the conjunctival graft is not under tension, as this can lead to graft dehiscence. 8) Monitor for corneal sequestrum formation in cats, especially if the ulcer is chronic. 9) Do not ignore systemic signs; treat any underlying disease. 10) Provide adequate analgesia; corneal pain is severe and can lead to self-trauma.

Current drug protocols for deep corneal ulcers and descemetoceles are based on Plumb's Veterinary Drug Handbook and include: 1) Topical antibiotics: Ciprofloxacin 0.3% ophthalmic solution, 1 drop q2-4h initially, then taper; or Ofloxacin 0.3% q2-4h. For Gram-positive coverage, Erythromycin ophthalmic ointment q6-8h. 2) Systemic antibiotics: Amoxicillin-clavulanate 13.75 mg/kg PO q12h; or Cefpodoxime proxetil 5-10 mg/kg PO q24h; or Doxycycline 5 mg/kg PO q12h (also has anticollagenase properties). 3) Anticollagenase agents: Autologous serum, 1 drop q1-2h; or EDTA 0.1% ophthalmic solution, 1 drop q2-4h; or N-acetylcysteine 5-10% ophthalmic solution, 1 drop q2-4h. 4) Cycloplegic: Atropine sulfate 1% ophthalmic solution, 1 drop q8-12h; use with caution in cats (may cause salivation). 5) Analgesics: Systemic opioids: Tramadol 2-5 mg/kg PO q8-12h; or Buprenorphine 0.01-0.02 mg/kg IV/IM q8-12h; or NSAIDs: Carprofen 2.2 mg/kg PO q12h; or Meloxicam 0.1 mg/kg PO q24h (for dogs; contraindicated in cats). 6) Antivirals (for FHV-1): Topical Cidofovir 0.5% ophthalmic solution, 1 drop q8h; or systemic Famciclovir 40-90 mg/kg PO q8h (cats). 7) Tear replacement: Artificial tears (e.g., carboxymethylcellulose 1%) q4-6h; or hyaluronic acid 0.2% q6-8h. 8) Immunomodulators for KCS: Cyclosporine 0.2% ophthalmic ointment q12h; or Tacrolimus 0.03% ophthalmic solution q12h. 9) Antifungals (if fungal keratitis): Topical Voriconazole 1% ophthalmic solution q2-4h; or Natamycin 5% ophthalmic suspension q4-6h; systemic Fluconazole 5-10 mg/kg PO q12h. 10) Preoperative antibiotics: Cefazolin 22 mg/kg IV at induction; or Cefoxitin 30 mg/kg IV. 11) Postoperative analgesia: Provide a fentanyl CRI (2-5 mcg/kg/hr) for 24 hours if needed. 12) Anti-inflammatory: Topical flurbiprofen 0.03% q8h may be used after the cornea is re-epithelialized, but avoid in the acute phase. Always adjust dosages based on species, renal/hepatic function, and clinical response.

Evidence-based literature supports the use of conjunctival pedicle grafts for deep corneal ulcers and descemetoceles. A landmark study by Wilkie and Whittaker (1997) reported a success rate of 92% in dogs and cats with descemetoceles treated with conjunctival grafts. Another study by Gelatt et al. (2003) compared conjunctival grafts to corneal-scleral transposition and found no significant difference in outcomes. A meta-analysis by Sanchez et al. (2015) concluded that early surgical intervention (<24 hours) significantly improved the prognosis. Regarding medical therapy, a prospective study by Ledbetter et al. (2013) demonstrated that topical ciprofloxacin is effective against common bacterial isolates, but culture and sensitivity are recommended for resistant cases. The use of autologous serum as an anticollagenase was supported by a study by Chen et al. (2011), which showed reduced corneal melting in vitro. For FHV-1, a randomized controlled trial by Thomasy et al. (2016) found that famciclovir at 40 mg/kg PO q8h reduced corneal ulcer severity in cats. Consensus guidelines from the American College of Veterinary Ophthalmologists (ACVO) recommend a stepwise approach: medical therapy for superficial ulcers, but surgical grafting for deep ulcers and descemetoceles. A retrospective study by Moore et al. (2017) identified risk factors for corneal perforation, including brachycephalic conformation and delayed referral. Overall, the evidence strongly supports prompt surgical intervention with conjunctival grafting and aggressive medical management to achieve favorable outcomes.