Immunopathogenesis of keratoconjunctivitis sicca in the dog.

Keratoconjunctivitis sicca (KCS), more commonly known as dry eye, is an inflammatory condition of the ocular surface caused by a pathologic reduction in the aqueous component of the tear film. It is seen commonly in the dog and defined as a Schirmer tear test with a reading of less than 10 mm in one minute. While KCS may be caused by neurological disease or drug toxicity, most cases are immune-mediated. Whereas the immunological basis of autoimmune KCS has been extensively investigated in humans and experimental rodent models, little research has been undertaken in the dog. It is hoped that this review spurs further research into the etiopathogenic factors in canine KCS.     

Diagnosis and treatment of keratoconjunctivitis sicca in the dog

Keratoconjunctivitis sicca (KCS) is a relatively common eye disease in the dog. The diagnosis is discussed, particularly of the early or mild case. The various types of medical treatment are described, including replacement therapy with artificial tears and ocular inserts, as well as other preparations; lacrimogenics; and other forms of medical treatment, including antibiotics, corticosteroids, mucolytics and hormones. Contraindicated drugs and agents are listed. Surgical treatments, including punctal occlusion, tarsorrhaphy, conjunctival flaps, contact lenses, superficial keratectomy, as well as parotid duct transposition, are discussed and the procedure indicated which is best suited to the case. The choice of treatment according to the severity of the KCS is also given.     

Corneal stromal sequestration and keratoconjunctivitis sicca in a horse

A 19-year-old Shetland pony presented with unilateral ocular discomfort and abnormal ocular appearance. Keratoconjunctivitis sicca, ulcerative keratitis and brown discoloration of the corneal stroma were identified on ophthalmic examination. The etiology of keratoconjunctivitis sicca was not determined in this case. For practical and financial reasons, the owners requested enucleation of the affected eye. Histopathologic examination revealed extensive loss of corneal epithelium overlying a zone of hypereosinophilic, degenerate, and necrotic corneal stroma. This well-circumscribed region of corneal stromal sequestration was surrounded by stromal vascularization, and an intense inflammatory, predominantly polymorphonuclear, cellular infiltrate. The clinical and histopathologic features of this case were considered remarkably similar to those observed in feline corneal stromal sequestration.     

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.     

Keratoconjunctivitis sicca and diabetes mellitus in a dog.

Diabetes mellitus and keratoconjunctivitis sicca were diagnosed in a female Poodle. The dog was treated for diabetes and keratoconjunctivitis sicca until blood glucose concentrations were within normal limits. Treatment for keratoconjunctivitis sicca was suspended then, and signs of this disorder did not appear again. Most of the factors known to predispose to keratoconjunctivitis sicca were not applicable to this dog. On the basis of observations made in this dog, we suggest that diabetes mellitus and keratoconjunctivitis sicca may be linked. Clinical signs of the disorders developed simultaneously and resolved when diabetes mellitus was controlled with insulin.     

Treatment of keratoconjunctivitis sica in a dog

An eight-year-old Collie dog was treated for keratoconjunctivitis sica of both eyes. Initial medical treatment for five months was of little use. Bilateral parotid duct transfer was performed and subsequently the eyes have remained constantly moist, although pigmentation and scarring to both corneas restricts vision.     

Infrared ocular thermography in dogs with and without keratoconjunctivitis sicca

Infrared thermography was used to measure temperature differences of the corneal surface between nasal and temporal limbus regions and central cornea of normal dogs and dogs with keratoconjunctivitis sicca (KCS), in order to establish temperature values in normal canine eyes and in patients with decreased Schirmer tear tests (STT) values. Dogs investigated were all either patients seen at the Veterinary Teaching Hospital of Federal University of Paraná or normal dogs that belonged to the same institution. STT were performed in all eyes. A total of 40 control eyes (STT ≥15 mm/min) and 20 eyes with low STT values (STT ≤14 mm/min) were examined. The mean STT value for eyes with normal STT values was 22.9 ± 3.9 mm/min (mean ± standard deviation), and the mean STT value for eyes with low STT value was 7.2 ± 4.8 mm/min. The mean corneal temperature was significantly lower in eyes with low STT values than in control eyes (P < 0.0001). The following significant correlations were found: (i) Schirmer and breakup time (BUT) (P = 0.0001, r = 0.5); (ii) STT values and corneal surface temperature (P = 0.001, r = 0.256); (iii) STT values and age (P = 0.0001, r = ?0.448); (iv) age and corneal surface temperature (P = 0.0001, r = ?0.281); and (v) BUT and corneal surface temperature (P = 0.0001, r = 0.36). Thermography is a method that can differentiate between eyes with normal and abnormal STT values. In the future, thermography might be incorporated as part of the ophthalmic examination and perhaps become a popular ancillary test for the diagnoses of ocular surface disorders.     

Treatment of keratoconjunctivitis sica in a dog

An eight-year-old Collie dog was treated for keratoconjunctivitis sica of both eyes. Initial medical treatment for five months was of little use. Bilateral parotid duct transfer was performed and subsequently the eyes have remained constantly moist, although pigmentation and scarring to both corneas restricts vision.     

Canine keratoconjunctivitis sicca: disease trends in a review of 229 cases

OBJECTIVES: To investigate the disease patterns in dogs with keratoconjunctivitis sicca referred to the University of Glasgow Small Animal Hospital. METHODS: A retrospective study of 229 cases was carried out. RESULTS: There were 44 breeds in the study, with four breeds, English cocker spaniels, cavalier King Charles spaniels, West Highland white terriers and shih-tzus, making up 58 per cent of the cases. Among these four breeds, two breed-dependent disease patterns, one chronic and one acute, were identified. English cocker spaniels and West Highland white terriers had a mean age at onset of clinical signs of five years and one month and five years and six months, respectively, with more females affected than males. Clinical signs consisted predominantly of conjunctival hyperaemia and mucopurulent discharge, with a relatively low incidence of ulcerative keratitis. In contrast, cavalier King Charles spaniels and shih-tzus showed a more acute disease pattern with a biphasic age distribution at 0 to less than two years of age, and four to less than six and six to less than eight years of age, respectively, with more males affected than females and a significantly higher incidence of ulcerative keratitis in some cases resulting in corneal perforation. CLINICAL SIGNIFICANCE: The study reveals interbreed differences with respect to sex, age and risk of ulcerative keratitis which have not been detailed previously in a referral population.     

Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis in the cavalier King Charles spaniel

OBJECTIVES: To record a previously unreported congenital and hereditary condition affecting the eyes and skin in the cavalier King Charles spaniel. METHODS: Nineteen cases (13 litters) were investigated, with particular reference to eye and skin clinical signs. In addition, five generation pedigrees were obtained and studied from all cases with the exception of one. RESULTS: The eye signs were due to keratoconjunctivitis sicca, a common ocular disease in the dog, but rarely of congenital origin. The skin signs were of an ichthyosiform dermatosis; ichthyosis being a rare skin disease in the dog. In human beings, ichthyosis is a similar disease, mainly inherited and with a neonatal onset, and sometimes accompanied by other developmental defects. In the cavalier King Charles spaniel, the coat abnormality was noted at birth by the breeders as a 'curly coat', with deterioration of the skin signs as the animal became adult. CLINICAL SIGNIFICANCE: These two conditions occurring together in this breed is well recognised by some breeders but rarely by the veterinary profession. Successful treatment is not possible, although some improvement, particularly of the keratoconjunctivitis sicca, can be obtained. The probable hereditary nature of the condition is an important factor for control.