Feline corneal disease

The cornea is naturally transparent. Anything that interferes with the cornea's stromal architecture, contributes to blood vessel migration, increases corneal pigmentation, or predisposes to corneal edema, disrupts the corneas transparency and indicates corneal disease. The color, location, and shape and pattern of a corneal lesion can help in determining the underlying cause for the disease. Corneal disease is typically divided into congenital or acquired disorders. Congenital disorders, such as corneal dermoids are rare in cats, whereas acquired corneal disease associated with nonulcerative or ulcerative keratitis is common. Primary ocular disease, such as tear film instability, adenexal disease (medial canthal entropion, lagophthalmus, eyelid agenesis), and herpes keratitis are associated with the majority of acquired corneal disease in cats. Proliferative/eosinophilic keratitis, acute bullous keratopathy, and Florida keratopathy are common feline nonulcerative disorders. Nonprogressive ulcerative disease in cats, such as chronic corneal epithelial defects and corneal sequestration are more common than progressive corneal ulcerations.     

Use of thermokeratoplasty for treatment of ulcerative keratitis and bullous keratopathy secondary to corneal endothelial disease in dogs: 13 cases (1994-2001)

OBJECTIVE: To evaluate the outcome of thermokeratoplasty for treatment of ulcerative keratitis and bullous keratopathy secondary to corneal endothelial disease in dogs. DESIGN: Retrospective study. ANIMALS: 13 dogs. PROCEDURES: Medical records from 1994 to 2001 for dogs evaluated because of ulcerative keratitis and bullous keratopathy and treated with thermokeratoplasty were reviewed. RESULTS: There were 7 spayed females, 5 castrated males, and 1 sexually intact male, ranging from 6 to 16 years of age. Ten dogs had endothelial degeneration, and 3 dogs had breed-related endothelial dystrophy. All dogs had bullous keratopathy, characterized by microbullae formation that was detected via biomicroscopy. Recurrent or nonhealing corneal ulcers were detected unilaterally in 5 dogs and bilaterally in 8 dogs. Mean +/- SD duration from thermokeratoplasty until ulcerations were healed for all dogs was 2.2 +/- 1.1 weeks. All dogs that underwent thermokeratoplasty for nonhealing corneal ulceration secondary to endothelial disease and corneal edema had epithelial wound healing and resolution of corneal ulceration. Mean duration of treatment (ie, topical treatment required until resolution of ulceration) was significantly less after thermokeratoplasty than duration of treatment (with multiple treatments) prior to referral. CONCLUSIONS AND CLINICAL RELEVANCE: It may be necessary to perform thermokeratoplasty of the entire cornea to prevent recurrence of ulcerations in areas that have not been treated with thermokeratoplasty.     

Corneal epithelial disease.

This article reviews conditions that primarily affect the corneal epithelium as distinct from corneal stromal diseases. Corneal ulceration is discussed elsewhere in this issue. The other corneal conditions include a variety of more subtle epithelial disease,which might colloquially be termed epitheliopathies, as well as uninfected indolent superficial ulcerations, corneal neoplasia, and eosinophilic keratitis. The fungal plaque is an unusual and somewhat chronic form of epithelial infection. Although less common than corneal ulcers, this collection of lesions may present uniquely challenging obstacles to diagnosis and identification of a cure. Newer therapies and surgical strategies are discussed.     

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.     

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.     

Bacterial corneal diseases in dogs and cats

Corneal diseases are very common in small animals. Corneal disease associated with bacterial agents is frequent in the dog and maybe less frequent in the cat. The medical history, important steps of the ophthalmic examination, and the ophthalmic diagnostic tests that are relevant in such corneal conditions are outlined. Bacterial corneal diseases in dogs and cats are most commonly considered in one of two categories--bacterial ulcerative keratitis and corneal abscesses. The clinical aspects of these two entities as well as the therapeutic strategies available for general practitioners and ophthalmologists are discussed. Ulcerative keratitis is frequent; it represents the most common ocular diseases in dogs and cats. Because some of these corneal ulcers can be very severe, progress rapidly, and therefore are sight threatening, the crucial steps of their diagnosis and management are stressed. The use of a magnification system, fluorescein dye, and corneal cytology and culture, if indicated, is necessary for diagnosis at an early stage of the disease. The treatment of bacterial ulcerative keratitis should eradicate the infection, reduce or stop the corneal destruction and support the corneal structures, control the uveal reaction and the pain associated with it, and minimize the scarring. The prognosis depends on the stage and the severity of the corneal ulceration, the etiology of the condition, and the therapeutic choice. A close follow-up of animals with corneal ulceration is highly recommended because corneal ulcers can progress rapidly.     

Efficacy of two chondroitin sulfate ophthalmic solutions in the therapy of spontaneous chronic corneal epithelial defects and ulcerative keratitis associated with bullous keratopathy in dogs

OBJECTIVE: To determine the efficacy of two antimicrobial-chondroitin sulfate ophthalmic solutions in the therapy of spontaneous chronic corneal epithelial defects (SCCED) and ulcerative keratitis associated with bullous keratopathy in dogs. ANIMALS STUDIED: Eighty dogs with SCCED and 14 dogs with ulcerative keratitis associated with bullous keratopathy. PROCEDURE: Following manual debridement of nonadherent epithelium, dogs were treated topically with a chondroitin sulfate ophthalmic solution containing either tobramycin or ciprofloxacin. Patients were re-evaluated at 2-week intervals for 4 weeks. RESULTS: After 2 weeks of treatment, 53.6% of eyes with SCCED and 17.6% of eyes with ulcerative keratitis associated with bullous keratopathy had healed. After 4 weeks of treatment, 81.0% of eyes with SCCED and 23.5% of eyes with ulcerative keratitis associated with bullous keratopathy had healed. There were no statistically significant differences in healing percentages between the tobramycin-chondroitin sulfate solution treatment groups and the ciprofloxacin-chondroitin sulfate solution treatment groups. Two dogs with SCCED, one treated with the tobramycin-chondroitin sulfate solution and the other treated with the ciprofloxacin-chondroitin sulfate solution, developed sterile corneal stromal abscesses during the study. CONCLUSIONS: Topical therapy with an antimicrobial-chondroitin sulfate ophthalmic solution combined with manual debridement of nonadherent epithelium compares favorably with other published medical and surgical therapies for SCCED; however, these compounds are only equivocally more effective than therapy with manual debridement alone. These solutions appear to be ineffective in the treatment of ulcerative keratitis associated with bullous keratopathy. The significance of the two cases of corneal stromal abscessation is unknown at this time and warrants further investigation.     

Primary central corneal hemangiosarcoma in a dog

Purpose To report a case of primary central corneal hemangiosarcoma in the dog. Methods An 11‐year‐old, neutered, female, German shepherd mixed breed dog was referred to the Hospital Veterinario Sierra de Madrid (Spain) for evaluation of an enlarging corneal mass of the left eye (OS). The dog was predominantly housed outdoors and was diagnosed with a history of chronic superficial keratitis of both eyes (OU) by the referring veterinarian. The corneal mass was resected by routine superficial keratectomy and submitted for histopathology and Factor VIII immunohistochemical staining. Results The mass was diagnosed as a corneal hemangiosarcoma with complete excision. Postoperatively, the keratectomy site healed without complication and there was no evidence of recurrence three and a half months postoperatively. Complete systemic evaluation, including abdominal ultrasound and CT scan of the head and thorax, indicated no other detectable neoplasia in the dog. Discussion Outdoor housing and ultraviolet exposure, breed, and chronic superficial keratitis were all suspected as contributing factors to the development of a primary corneal hemangiosarcoma. Surgical removal and postoperative treatment for chronic superficial keratitis provided effective therapy.     

Keratitis and periocular lesions associated with equine herpesvirus‐3 in a 3‐month‐old filly

A 3‐month‐old Quarter Horse filly presented with corneal ulceration in the right eye with extensive coalescing periocular ulcerations, erosions, and cutaneous crusts. Similar periocular lesions were present around the left eye, on the gingival mucosa, and on the cutaneous and mucosal surfaces of the lips. Based on the severity of the filly's corneal lesions, expense and duration of treatment, euthanasia was elected. Histological post mortem examination revealed numerous hyperplastic and/or dysplastic epithelial cells adjacent to areas of ulceration and erosion with intranuclear viral inclusion bodies. Equine herpesvirus‐3 (EHV‐3) was identified by polymerase chain reaction from the right cornea and lip. The virus was isolated from the right cornea, right eyelid and lip. The dam presented with multifocal to coalescing perineal vesicles. EHV‐3 was confirmed by polymerase chain reaction from the vulvar lesions and the mare recovered spontaneously. This is the first case of EHV‐3 corneal infection reported in horses and emphasises that EHV‐3 should be included as a differential diagnosis for vesicular lesions involving the equine periocular and oronasal epithelium.     

Histopathologic evidence of capecitabine corneal toxicity in dogs

In an experimental model of transplant rejection, renal transplants were performed on 6 mixed-breed dogs. Capecitabine (CPC) was administered as an oral immunosuppressive agent. All recipients received systemic CPC, cyclosporine (CSA), prednisolone, and famotidine throughout the study. Two dogs developed superficial keratitis, which was characterized by multifocal geographic erosions, superficial corneal epithelial pigmentation, and corneal neovascularization. These clinical signs correlated with the dose of CPC given, whereas other drug doses remained unchanged. After euthanasia, routine histologic sections were stained with hematoxylin and eosin and with alcian blue periodic acid-Schiff for light microscopic evaluation. Ocular histopathologic abnormalities were limited to neovascularization and inflammatory infiltrate of the anterior corneal stroma and abnormal basal cell morphology, disorganization, thinning, and pigmentation of the corneal epithelium. The purpose of this communication is to describe the clinical and histopathologic evidence of CPC corneal toxicity in dogs.     

Superficial keratectomy and topical mitomycin C as therapy for a corneal squamous cell carcinoma in a dog

A 10-year-old female West Highland white terrier was presented with refractory hyperplastic keratitis of the left cornea of one month's duration. At this time, a vascularised and rough lesion 5 mm in diameter was observed on the left cornea. No other abnormality was recognised on the affected eye. The corneal neoplasm was surgically removed and histologically diagnosed as a squamous cell carcinoma. For two months after the surgery, 0.04 percent mitomycin C (MMC) eye drops were applied as adjuvant chemotherapy. Primary corneal squamous cell carcinoma with no history of keratoconjunctivitis sicca is rare in dogs. In the present report, surgical removal of the neoplasm was combined with the topical administration of the anticancer drug mitomycin C and a good prognosis was obtained. The result indicates that the combination treatment used in this case may be an appropriate therapeutic choice for corneal squamous cell carcinoma in dogs.     

Clinical management of superficial complicated corneal ulcerations infected with newly identified fastidious bacteria with unknown antibiotic sensitivity in three horses

This case series addresses a clinical approach to a specific type of infected corneal ulceration in horses; the slow-healing superficial complicated corneal ulceration involving a fastidious or possibly newly identified bacteria for which no antibiotic sensitivity can be determined. These corneal ulcerations present as superficial, nonhealing lesions that appear infected based on cellular infiltration of the cornea. Because they are superficial, they do not appear to be as serious to the referral veterinarian as deep stromal corneal ulcerations. However, superficial corneal ulcerations are complicated and slow healing, ultimately frustrating both owners and primary care clinicians. Culture results are often negative, or implicate a newly identified bacteria with no known antimicrobial sensitivity in horses.     

Matrix metalloproteinase inhibition in corneal ulceration.

The primary objective of current treatment strategies for infectious keratitis is to sterilize the ulcer as rapidly as possible with topically administered antibiotics. Ulcerative processes can proceed in some cases, despite the absence of microbes, as a result of remaining corneal and tear film MMPs. Combining antibiotic therapy with MMP inhibitors can speed corneal healing, because MMPs play an important role in corneal ulceration and stromal liquefaction. MMPs from the rabbit, horse, and human being are inhibited by metal-binding agents EDTA, NAC, and doxycycline as well as by the serum antiprotease alpha2-macroglobulin. It is not yet certain which proteinase inhibitor has the most favorable therapeutic index for clinical use, although we prefer serum because of its effects on multiple types of proteinases. The MMP inhibitors do have significant therapeutic promise in the treatment of corneal ulceration.     

Profiles of matrix metalloproteinase activity in equine tear fluid during corneal healing in 10 horses with ulcerative keratitis

OBJECTIVE: Levels of tear film matrix metalloproteinases (MMPs) activity are significantly elevated in horses with ulcerative keratitis and contribute to the excessive breakdown of stromal collagen. Changes in the amount of proteolytic activity in horse tear film during corneal healing and stromal remodeling have not yet been reported, but we hypothesize they should decrease. In the present study we analyzed serial tear fluid from horses with ulcerative keratitis to identify any changes in MMP activity during corneal healing and stromal remodeling. PROCEDURES: Samples of tear fluid were obtained from both eyes of 10 horses with ulcerative keratitis on the day of admission (day 1) at the hospital and then at various time points until complete healing of the cornea. Tear film MMP2 and MMP9 activity was determined by quantitative gelatin zymography. In all cases medical treatment included topical applications of equine serum, antibiotics, atropine and systemic administration of anti-inflammatory drugs. Surgical procedures were performed in several cases on day 2 in addition to the medical treatment. RESULTS: The mean total MMP activity (+/- SD) measured in relative standard units (RSU) in the tear fluid of the ulcerated eye (2.44 +/- 1.44) of the 10 horses was significantly higher than the mean in the contralateral eye (0.81 +/- 0.68) (P = 0.006), on the day of admission at the VMTH. The mean MMP activity in these ulcerated eyes significantly decreased (-82.4%) between the first day of admission and the day when the ulcer had completely healed (P = 0.0002). The activity level in the healed eye (0.43 +/- 0.17) was not significantly different to the one in the contralateral eye (0.36 +/- 0.18) on the day of complete corneal healing (P = 0.374). The level of MMP activity in the contralateral eye also decreased from 0.81 +/- 0.68-0.36 +/- 0.18 but this decrease (56%) was not significant (P = 0.069). CONCLUSIONS: Ulcerative keratitis in horses is associated with initially high levels of tear film proteolytic activity that decrease as the ulcers heal. The success of medical and surgical treatment of the corneal ulcers is reflected by the enzyme activity in tears. In horses successful treatment does lead to a rapid reduction in tear film proteolytic activity that corresponded with the improvement in the clinical signs of corneal ulceration. Measurement of MMP activity in the tear film might represent a way to monitor the progression of corneal healing in horses with ulcerative keratitis.     

Radiotherapy for canine chronic superficial keratitis using soft X-rays (15 kV)

Objective  To evaluate the effect of soft X-ray therapy in the treatment of refractory chronic superficial keratitis (CSK).
Animals studied  Thirteen dogs with severe CSK, that had been refractory to prior medical and/or surgical therapy were treated with soft X-ray therapy.
Procedures  Both corneas of each dog were irradiated with soft X-rays (15 kV), to a total dose of 30 Gy, administered as two fractions over 48–96 h. Treatment was carried out under deep sedation in all dogs. Three dogs were treated by superficial lamellar keratectomy 48 h prior to radiotherapy. Changes in the extent of corneal pigmentation, pigment density and corneal vascularization were documented using a semi-quantitative grading scheme, schematic drawings and clinical photographs.
Results  Only minor, transient adverse effects of treatment, such as photophobia, epiphora and blepharitis were noted. Overall the effect of soft X-rays on the course of the keratitis was superior when compared to the effect of Sr-90 irradiation that had been determined in a previous study.
Conclusion  Soft X-ray irradiation combined with keratectomy is a safe and effective new treatment option for severe and advanced CSK with significant visual impairment due to corneal pathology.     

Effects of radiofrequency hyperthermia on the healthy canine cornea

Radiofrequency hyperthermia was used to induce axial corneal lesions in the eyes of 10 dogs. Clinical observations were continued for up to 6 months, using biomicroscopy and indirect ophthalmoscopy. Eyes were harvested at intervals for light and electron microscopic evaluation. Clinical alterations included immediate corneal opacification and epithelial disruption at the site of electrode contact. Ulcerative keratitis persisted for 4 to 6 days, accompanied by anterior uveitis. Additional corneal changes included stromal thinning, edema, and vascularization. Final evaluation revealed negligible alterations in corneal contour or clarity 6 months after treatment. Microscopically, epithelial and superficial stromal necrosis preceded epithelial loss. Stromal alterations included edema (associated with focal endothelial detachments), vascularization, and inflammatory cell infiltration. Recovery was characterized by keratocytic hyperplasia and hypertrophy, epithelial proliferation, and stromal condensation.     

The treatment of corneal ulcers

The anatomy of the cornea and the method of assessing corneal damage are described. The many causes of ulcerative keratitis are stated. The general principles of treatment are set down. Particular treatments are then described according to the causative agent and to the type of ulcer. In a paper of this length it will not be possible to consider the specific treatment of each and every type of corneal ulceration that occurs in the dog. The causes of ulcerative keratitis are many and this paper will consider the general principles involved and, in particular, some of the more common varieties of corneal ulcer. Résumé. On a décrit l'anantomie de la cornée et la méthode pour évaluer le dommage cornéen. Les nombreuses causes de la kératite à hypopyon sont réglées. Les principes généraux du traitement sont posés. Puis les traitements particuliers sont décrits selon l'agent pathogène et le type de l'ulcère. Zusammenfassung . Die Anatomie von der Hornhaut und die Methode, die kornealen Schäden zu abzuschätzen, werden beschrieben. Viele Ursachen von Hypopyonkeratitis werden angegeben. Die allgemeinen Grundsätze der Behandlung werden aufgeschoben. Dann werden besondere Behandlungen nach dem verursachenden Mittel und nach dem Typ vom Geschwür beschrieben.     

Effects of cyclophotocoagulation with a neodymium:yttrium-aluminum-garnet laser on corneal sensitivity,intraocular pressure,aqueous tear production,and corneal nerve morphology in eyes of dogs

OBJECTIVE: To determine effects of cyclophotocoagulation via administration of 100 J with a neodymium:yttrium aluminum garnet (Nd:YAG) laser on corneal touch threshold (CTT), intraocular pressure (IOP), aqueous tear production, and corneal nerve morphology in eyes of dogs. ANIMALS: 15 dogs. PROCEDURE: Noncontact Nd:YAG laser was transsclerally applied (10 applications; 25 W for 0.1 seconds for each application to each of 4 quadrants) to the ciliary body of the left eye of 15 dogs; the right eye was the control eye. Corneal integrity, CTT, tear production as measured by the Schirmer tear test (STT), and IOP were evaluated for 14 days following laser treatment. On day 14, dogs were euthanatized, eyes harvested, and corneas stained with gold chloride. Major nerve bundles were analyzed by use of a drawing tube attached to a light microscope, and maximum diameters were measured by use of image analysis software. RESULTS: All laser-treated eyes had significantly higher CTT values, compared with control eyes. Six of 15 laser-treated eyes developed ulcerative keratitis. On most days, IOP was significantly lower in laser-treated eyes in both morning and evening. Laser-treated eyes had a significant decrease of approximately 1 nerve bundle/corneal quadrant. Values for STT or nerve bundle diameters did not differ significantly. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of 100 J with a Nd:YAG laser effectively reduced IOP while increasing CTT and caused a significant decrease in number, but not diameter, of major corneal nerve bundles. Nerve damage and corneal hypoesthesia are etiologic factors in ulcerative keratitis following Nd:YAG cyclophotocoagulation.     

Nutritionally variant streptococci associated with corneal ulcers in horses: 35 cases (1982-1988)

Nutritionally variant streptococci (NVS) are nutritionally deficient viridans streptococci that require pyridoxal for growth. Although NVS are pathogenic in human beings, they have not been considered to be pathogenic in domestic animals. In 1982 and 1983, 24 isolates of NVS were recovered from horses with ulcerative keratitis. A retrospective study was done to determine the incidence of NVS in horses with corneal disease. The medical records of 249 horses (259 eyes) examined for clinical signs of corneal disease were reviewed. Nutritionally variant streptococci were isolated from approximately 13.5% of horses with ulcerative keratitis.