Amniotic membrane transplantation for the treatment of feline corneal sequestrum: pilot study

Objectives To describe and evaluate the use of equine amniotic membrane trans‐plantation after lamellar keratectomy for the treatment of corneal sequestrum in cats. Methods Six cats (seven eyes) of various breed and ages with corneal sequestra were treated surgically with lamellar keratectomy and amniotic membrane transplantation. All the sequestra and a small piece of the amniotic membranes used for each surgery were submitted for histopathologic examination. Results Five of the seven eyes showed minimal level of scarring in the cornea and good transparency. No recurrences of the sequestra have been noted during the follow‐up period (3–9 months). One eye had necrosis of the amniotic membrane 2 weeks after the surgery. The sequestrum of this eye showed a high level of bacterial contamination on histopathology. Three months later the same cat developed a descemetocele in the area where the necrotic amniotic membrane was rejected. A second eye developed a perforation under the amniotic membrane two weeks after the surgery. The sequestrum of this eye was deep and without vascularization. Conclusion Amniotic membrane transplantation after lamellar keratectomy was a valid procedure for surgical treatment of corneal sequestrum in cats. The procedure resulted in excellent cosmesis and functional vision in five of seven eyes; although case selection is important, particularly to exclude the very deep and non‐vascularized sequestra.     

Lamellar keratoplasty for the treatment of feline corneal sequestrum

A lamellar keratoplasty was used to treat corneal sequestrum in four Persian cats (six eyes). Following a superficial keratectomy, lamellar corneal allografts (feline corneal tissue) or heterografts (canine corneal tissue) which had been preserved at –20 °C were placed in the recipient cornea. All grafts became optically transparent within 2 months following surgery and no recurrences of the sequestrum have been noted during the follow-up period (4–30 months). We conclude that feline corneal sequestrum may be successfully treated with feline or canine donor corneal tissue using this technique.     

Cytologic findings, and feline herpesvirus DNA and Chlamydophila felis antigen detection rates in normal cats and cats with conjunctival and corneal lesions

Samples were collected from 36 cats with feline herpesvirus (FHV-1)-related ocular disease (conjunctivitis, epithelial or stromal keratitis, or corneal sequestration), and 17 cats without ocular changes. Corneoconjunctival swabs, scrapings and biopsies were tested in various combinations for presence of FHV-1 DNA using single round (sr) polymerase chain reaction (PCR) and nested PCR (nPCR). Additional swabs from the inferior conjunctival fornix were tested by enzyme-linked immunosorbent assay for Chlamydophila felis antigen. Cytologic evaluation was carried out on conjunctival (cats with conjunctivitis) and corneal (cats with keratitis) cytobrush preparations. FHV-1 DNA was detected by PCR in 14 (39%) cats with ocular disease and 1 (6%) of the control group. Agreement between srPCR and nPCR results was significant (P < 0.01). FHV-1 DNA was detected in 3/7 cats with conjunctivitis, 5/6 cats with epithelial keratitis, 3/11 cats with stromal keratitis, and 3/12 cats with corneal sequestration. There was a significant association (P = 0.0027) between viral presence and epithelial keratitis. However, no significant association was found between viral presence and conjunctivitis (P = 0.059), stromal keratitis (P = 0.15), or corneal sequestration (P = 0.18). With respect to FHV-1 DNA detection, intersample agreement was significant (P < 0.03). No sampling technique seemed more likely than another to harvest detectable viral DNA, except for cats with corneal sequestrum in which viral DNA was not detected using corneoconjunctival swabs. FHV-1 DNA was detected in 6/9 samples with intranuclear inclusion bodies and in 6/7 cats with eosinophils on cytologic examination. All samples tested negative for C. felis antigen.     

Mineralized corneal sequestrum in a cat.

An 8-month-old 3-kg (6.6-lb) sexually intact male cat was evaluated for chronic refractory keratitis and a corneal plaque that developed after treatment with a corticosteroid-containing ophthalmic preparation. Pertinent ophthalmic findings included blepharospasm, conjunctivitis, corneal vascularization, and a tan raised corneal plaque with a dense and gritty composition. Lamellar keratectomy was performed to excise the plaque. The cornea healed with mild scarring. Histologic examination revealed extensive coagulation necrosis and mineralization of the corneal stroma with increased inflammatory cells, blood vessels, and fibrosis, which is compatible with a diagnosis of mineralized corneal sequestrum. The history suggested chronic feline herpesvirus-1 (FHV-1)-induced keratoconjunctivitis as the underlying cause. Topical corticosteroid administration may have potentiated the preexisting corneal necrosis and initiated mineralization. To our knowledge, mineralization of a corneal sequestrum in a cat has not been reported in a clinical case but has been reported in cats experimentally infected with FHV-1.     

Corneal stromal sequestration in a dog

A case of corneal sequestrum in a 9-year-old Shih Tzu is reported. On the ophthalmic examination a brown-pigmented ulcer with mild edema and corneal vascularization was present. The brownish plaque was facing an inferior palpebral tumor. A superficial keratectomy followed by a grid keratotomy and removal of the palpebral mass were performed. Histological findings revealed an inflammatory cell infiltration underneath the acellular stromal layers. No melanin granules were observed. No vascular infiltration was present within the necrotic stroma. The surgical area healed and no recurrence has been reported by the owners at the time of writing. To the authors' knowledge, this is the first report of a corneal sequestrum in a dog.     

Nonhealing corneal ulcers in cats: 29 cases (1991-1999)

OBJECTIVE: To compare mean healing times after debridement, debridement with grid keratotomy, and superficial keratectomy in cats with nonhealing corneal ulcers. DESIGN: Retrospective study. ANIMALS: 29 cats with 36 nonhealing corneal ulcers. PROCEDURE: Medical records of cats with nonhealing corneal ulcers were reviewed. Signalment, duration of clinical signs, ophthalmic abnormalities, and response to various treatment protocols were recorded. RESULTS: Mean age of affected cats was 7 years, 8 months. Affected breeds included domestic shorthair (17 cats), Persian (9), Himalayan (2), and Siamese (1). Clinical signs were evident for approximately 2 weeks prior to referral. Both eyes were affected in 4 cats. Mean healing time of ulcers treated with superficial debridement was 30 days. Mean healing time of ulcers treated with superficial debridement and grid keratotomy was 42 days. Superficial keratectomy was performed on 2 eyes and resulted in a healing time of 2 weeks. Formation of a corneal sequestrum was evident in 2 of 21 eyes treated with superficial debridement. Formation of a corneal sequestrum was evident in 4 of 13 eyes treated with superficial debridement and grid keratotomy. CONCLUSIONS AND CLINICAL RELEVANCE: Brachycephalic cats appear to be predisposed to developing nonhealing corneal ulcers. The combination of superficial debridement and grid keratotomy did not decrease mean healing time of nonhealing ulcers, compared with superficial debridement alone. Grid keratotomy may predispose cats with corneal ulcers to develop a corneal sequestrum.     

Corneal sequestrum in the cat. Repair using a tarso-conjunctival pedicle flap

Corneal sequestrum was diagnosed upon clinical examination of 12 cats. The cornea of seven were examined histologically and had focal necrosis and inflammation of the stroma and epithelium. As the simple excision of the corneal lesions had been unsuccessful in two of the cats, repair of these was effected by construction of a tarso-conjunctival pedicle flap after the excision of the sequestrum.     

Corneal sequestrum in the cat. Repair using a tarso-conjunctival pedicle flap

Corneal sequestrum was diagnosed upon clinical examination of 12 cats. The cornea of seven were examined histologically and had focal necrosis and inflammation of the stroma and epithelium. As the simple excision of the corneal lesions had been unsuccessful in two of the cats, repair of these was effected by construction of a tarso-conjunctival pedicle flap after the excision of the sequestrum.     

Feline corneal sequestrum: laboratory analysis of ocular samples from 12 cats

Feline corneal sequestrum is a common ocular condition typified by brown to black discoloration of the cornea. The nature of the discoloration has not been identified. The purpose of this study was to perform a laboratory investigation of ocular samples from 12 clinical cases of feline corneal sequestrum in an attempt to characterize the nature of the discoloration. The 12 cases were referred to the Ophthalmology Unit at the Animal Health Trust between April and September 2000, and were also part of a clinical review of 64 cases of feline corneal sequestrum described separately. Five laboratory techniques that are routinely performed at the Biomaterials Unit, Aston University were employed for analysis of the ocular samples. Ocular material included corneal sequestrum, tear samples, meibomian gland secretions, and bandage contact lenses from the 12 clinical cases. High-performance liquid chromatography data showed that total tear lipid in affected eyes was significantly lower than in control eyes (P = 0.016); total tear lipid in affected eyes was lower than in the unaffected, contralateral eyes of the same cat but the difference was not significant (P = 0.29). The presence of an unknown lipid class was observed in tears and meibomian secretions of affected, contralateral and control eyes. Scanning electron microscopy showed that the discoloration in affected corneas was not due to the presence of iron. Fluorescence spectroscopic analysis of sequestra, unaffected corneas and contact lenses (from affected and contralateral/unaffected eyes) showed that lipid and protein were present but did not play an important role in sequestra. Ultraviolet-visible light absorbance spectroscopy revealed a peak at 385 nm in unaffected corneas that was absent in sequestra and the difference was significant (P < 0.0001); this peak may be a characteristic feature of the normal feline cornea. The absorbance spectra displayed a peak at 280 nm in two sequestra suggesting that chromophore groups (e.g. melanin) were present. Optical microscopy performed on 10 sequestra revealed the presence of particles, which were consistent with the appearance of melanin particles, providing laboratory evidence that characterized the nature of the discoloration as melanin for the first time.     

A retrospective study of 30 cases of frozen lamellar corneal graft in dogs and cats

Frozen lamellar corneal grafts and nictitating membrane flaps were used in 18 dogs and 12 cats to repair deep corneal defects. In all dogs either melting corneal ulcers or descemetoceles were present. In the 12 cats, nine had either a melting corneal ulcer or descemetocele, two animals had acute bullous keratopathy, and one cat had corneal sequestrum. Initial vascularization with gradual clearing of the graft occurred during the first 45 days postoperatively. At 60 days postoperatively, all eyes were visual. Frequent postoperative complications included: focal dehiscence of the wound ( n  = 9); melting of part of the graft ( n  = 7); and pigmentation of the graft ( n  = 4). The frozen lamellar corneal graft was a very safe technique, and restored the tectonic and the optical function of the cornea. It provided the best results in corneas with nonperforating corneal defects. This technique provides poorer results when the cornea was perforated prior to surgery or during the surgical procedure.     

A comparison of corneal sensitivity between healthy cats and cats with corneal sequestra

In order to establish reference values for corneal sensitivity in ophthalmologically healthy persians (n = 40) and domestic short hair cats (n = 60) a prospective study was conducted. Furthermore corneal sensitivity in 48 cats with a corneal sequestrum was measured. Corneal sensitivity was recorded with the help of the aesthesiometer according to Cochet and Bonnet in five different corneal locations (central, nasal, dorsal, temporal, and ventral). The sensitivity for the central corneal region was recorded as amounting to 3.58 +/- 0.56 cm in ophthalmologically healthy domestic short hair cats and to 2.97 +/- 0.58 cm in healthy persian cats. The sensitivity of the central corneal area of a cat with a corneal sequester only amounts to 2.03 +/- 0.53 cm. Between the diseased and the healthy eyes no statistical difference could be demonstrated for any of the measured corneal locations. The sensitivity of the peripheral corneal locations is significantly lower than that of the central corneal region in all three groups examined.     

Determination of protein concentrations and their molecular weight in tears from cats with normal corneas and cats with corneal sequestrum.

Protein concentration was determined, using the Bradford technique, in tears from cats with normal corneas and from cats with corneal sequestrum. Tears from the former group contained 5.81 +/- 2.29 mg of protein/ml; those from corneal sequestrum-affected cats contained 6.21 +/- 2.21 mg/ml. Difference between the 2 values was not significant. Molecular weight determination was made, using 4 to 20% sodium dodecyl sulfate-polyacrylamide gels. Molecular mass of proteins ranged from 263 to 14 kDa. There was no detectable difference in the band patterns for the 2 groups.     

Heterologous penetrating keratoplasty for treatment of a corneal sequestrum in a cat

A corneal sequestrum was diagnosed in an 8-year-old, neutered male Burmese cat. A heterologous penetrating keratoplasty (PK) (fresh canine corneal tissue) was performed to restore a clear visual axis. A heterograft was selected in order to decrease the risk of viral transmission as a screened donor was not available. One month postoperatively the graft was vascularized and opaque. The owner failed to return for recheck examinations until 16 months postoperatively at which time only a faint central nebula remained.     

Bilateral parotid duct transposition for keratoconjunctivitis sicca in a Connemara stallion

A 7‐year‐old Connemara stallion was presented with a 4 month history of blepharospasm, recurrent corneal ulcerations, mucopurulent ocular discharge, and keratoconjunctivitis sicca (KCS) in both eyes unresponsive to medical therapy. Ophthalmic examination revealed lackluster corneas, axial corneal scarring and pigmentation with associated neovascularization, and absolute KCS in both eyes. Computed tomography scan and endoscopic evaluation of the upper airway and guttural pouches revealed no structural abnormalities to indicate neurogenic KCS. The stallion was diagnosed with immune‐mediated dacryoadenitis as all other causes of KCS were excluded. Parotid duct transposition (PDT) was performed in the right eye followed by PDT in the left eye 4 weeks later. The right PDT was functional 2 years post‐operatively with significant improvement in ocular comfort and reduced corneal fibrosis and neovascularization. The left PDT developed a salivary‐cutaneous fistula over the left masseter muscle post‐operatively due to avascular necrosis of the distal parotid duct (PD). Surgical reconstruction of the PDT using an expanded‐polytetrafluoroethylene (e‐PTFE) tube graft, an e‐PTFE tube graft to autogenous caudal auricular vein graft, and an autogenous saphenous vein graft were all unsuccessful. Tear production in the left eye improved at 1 year post‐surgery as a result of long term lacrostimulant therapy, and a permanent PD‐cutaneous fistula was performed on the left PD at the level of the ventral mandible. Bilateral PDT in the horse is effective in resolving clinical signs associated with KCS; however, morbidity associated with avascular necrosis of the transposed PD may be significant and can result in surgical failure.     

Use of conjunctival pedicle grafts in the management of feline keratitis nigrum

Feline keratitis nigrum (necrosis, sequestrum or sequestration) usually presents as a black plaque in the axial or paraxial cornea. Most cats can be treated by excision of the lesion and covering the defect with a third eyelid flap. This technique did not provide satisfactory results in some cases. This paper describes microsurgery using conjunctival pedicle grafting following keratectomy to provide a one step technique to manage recurrent feline keratitis nigrum, feline keratitis nigrum with full thickness lesions of corneal stroma and eyes also affected with keratoconjunctivitis sicca.     

Qualitative tear film and conjunctival goblet cell assessment of cats with corneal sequestra

OBJECTIVES: To evaluate the tear film qualitatively and conjunctival goblet cell numbers in cats with and without corneal sequestra. ANIMALS STUDIED AND PROCEDURES: This was a prospective evaluation of 11 cats with corneal sequestra and 14 control eyes that were either the contralateral normal eye when the sequestrum was unilateral or from control cats of similar age with no ocular disease. All cats in this study were examined by a veterinary ophthalmologist. The ophthalmic examinations included a neuro-ophthalmic evaluation, Schirmer tear tests, fluorescein staining, tear film break-up times, applanation tonometry, biomicroscopy, and indirect ophthalmoscopy. The palpebral conjunctiva at the dorsal nasal, ventral nasal, dorsal temporal and ventral temporal fornices were biopsied after topical anesthetic was applied to the cornea and conjunctiva. The conjunctival biopsies were fixed in formalin and sectioned routinely and stained with hematoxylin and eosin, and periodic acid-Schiff. These slides were examined by light microscopy by a blinded examiner. Goblet cell numbers were compared to conjunctival basal epithelial cell numbers by region. The goblet cell numbers by region from the eyes with sequestra was statistically compared to those from eyes without sequestra, with a student's paired t-test. Conjunctival swabs were collected from the cats with corneal sequestra and submitted for polymerase chain reaction for Herpes felis, Chlamydia psiitticia, and Mycoplasma felis. The corneal sequestra were removed by surgical keratectomy and fixed and stained routinely, and examined by light microscopy. RESULTS: No neurologic abnormalities were detected in any of the cats. The Schirmer tear tests (eyes with sequestra 14+/-5.1 mm/min; normal eyes 15+/-6.8 mm/min) and intraocular pressures (eyes with sequestra 21+/-6.6; normal eyes 22+/-5.8) were within normal reference ranges for cats. Biomicroscopic examinations revealed varied sizes and depths of brown- and amber-colored corneal sequestra. No abnormalities were noted on indirect ophthalmoscopic examinations. The tear film break-up time was 21 s (+/-12) for the normal eyes (n=14) and 14 s (+/-13) in eyes with corneal sequestra (n=11). The average goblet/epithelial cell ratios by region for the normal eyes and the eyes with sequestra respectively were 0.66, 0.56 for the dorsal nasal fornix, 0.68, 0.57 for the ventral nasal fornix, 0.63, 0.48 for the temporal dorsal fornix, and 0.55, 0.49 for the temporal ventral fornix. There were no significant differences in tear film break-up times and goblet cell numbers in eyes with corneal sequestra and those without sequestra. Three conjunctival swabs from two of 11 cats with sequestra were positive with PCR for Herpes felis virus. These included one cat with bilateral sequestra and one cat with unilateral corneal sequestrum. CONCLUSIONS: The pathogenesis of feline corneal sequestra does not appear to be linked primarily to abnormal goblet cell numbers, qualitative tear film abnormalities, and accelerated tear film break-up time.     

Superficial Osteitis and Sequestrum Formation as a Result of Skin Avulsion in the Horse

Metatarsal injuries with exposed bone are described in seven horses. Superficial osteitis and sequestrum formation occurred in six of the seven horses. The basic pathophysiology includes local vascular stasis leading to ischemic necrosis of osteocytes and establishment of bacterial infection within dead bone. Radiographic features of superficial osteitis and sequestrum formation include reactive periosteal new bone formation, an area of radiodense necrotic bone (sequestrum) surrounded by a radiolucent zone of granulation tissue, which in turn, is surrounded by an area of increased radiodensity (involucrum). The presence of a sequestrum may usually be confirmed radiographically by 12–14 days after injury. Surgical management included wound debridement, wound irrigation, bandaging or casting, sequestrectomy and skin grafting. Five of the seven patients required sequestrectomy, in one the sequestrum disappeared without removal. Mixed bacterial populations were commonly found in the wounds. No specific etiologic agent was associated with sequestrum formation.     

Corneal plaque containing levofloxacin in a dog

A 13‐year‐old castrated male Yorkshire terrier developed a corneal ulcer 2 weeks after intracapsular lens extraction (ICLE) in the right eye. The corneal ulcer was treated with levofloxacin eye drops. A plaque with a white luster developed in the central cornea 2 weeks after treatment with levofloxacin eye drops. The corneal plaque was surgically removed under inhalant anesthesia. The corneal plaque displayed antimicrobial activity against Escherichia coli. Furthermore, levofloxacin content in the plaque was confirmed by matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight (MALDI‐TOF/TOF) mass spectrometry (MS). The corneal ulcer completely resolved 2 weeks after the surgical removal of the corneal lesion and replacement of levofloxacin eye drops with tobramycin eye drops. Although the topical use of levofloxacin is unlikely to lead to corneal chemical deposits due to the high water solubility of the drug compared to other topical fluoroquinolones, this patient developed corneal plaque of the antibiotic drop.     

Ocular manifestations of feline herpesvirus.

Feline herpesvirus-1 (FHV-1) infection is ubiquitous in the domestic cat population worldwide. The most common clinical ocular manifestations of infection with FHV-1 are conjunctivitis and keratitis. This paper reviews the pathogenesis of feline herpesvirus-1 and discusses the various clinical ocular manifestations, diagnostic techniques and treatment of FHV-1-induced diseases. Ocular manifestations include: conjunctivitis, keratitis, stromal keratitis, keratoconjunctivitis sicca, ophthalmia neonatorium, symblepharon, corneal sequestrum, eosinophilic keratitis and anterior uveitis. Diagnostic techniques discussed include: virus isolation, fluorescent antibody testing, serum neutralising titers, ELISA and polymerase chain reaction. Various therapies are also discussed.     

Feline entropion: a case series of 50 affected animals (2003–2008)

Aim  To evaluate the signalment, clinical signs, and etiopathogenesis of entropion in 50 cats.
Methods  Signalment and history of 50 cases of entropion in cats presented to a referral ophthalmology clinic. Animals were examined with direct and indirect ophthalmoscopy and slit-lamp biomicroscopy. Animals were treated surgically with a Hotz-Celsus procedure and results of surgery were evaluated between 4 and 22 weeks.
Results  Sixteen cats were young (mean age 4.1 ± 3.6 years) with pre-existing irritative ocular surface conditions such as conjunctivitis, corneal ulceration or sequestrum. Twenty-six cats were relatively older (mean age 11.3 ± 2.2 years) with involutional entropion with or without enophthalmos, presumed to result from a reduction in orbital tissue. Five cats were Persians with entropion associated with brachycephalic facial anatomy, whereas three were entire young adult male Maine Coones with in-turning associated with excessive facial 'jowl' tissue. Surgical treatment was curative in the majority of cases after one surgery although an increased amount of eyelid tissue was required to be removed for correction compared with similar surgery in the dog.
Discussion  This study has shown that entropion in cats may be caused in young animals as a result of continued blepharospasm related to irritative causes such as conjunctivitis or corneal ulceration or in older animals with lid laxity or globe enophthalmos. Lid in-turning was also seen in Persian and Maine Coone breeds.