Causes, Diagnosis and Treatment of Keratitis in Pet Dogs
Keratitis is the general term for inflammation of the corneal tissue. It is characterized by corneal opacity (nebula), corneal neoplasm, corneal ulcer, corneal perforation and residual corneal macula. It can occur in all kinds of dogs, but is common in long-haired small breeds. Etiological analysis and treatment-effect statistics were carried out on 68 dogs with keratitis diagnosed and treated since May 2005. Most cases were caused by trauma, foreign bodies, inappropriate drugs and infection, and some had unknown causes. After treatment, 66 cases were cured, with a cure rate of 97.06%. Perforation caused by corneal ulcer is difficult to cure.
1 Case analysis
1.1 Breeds of affected dogs Among these 68 dogs with keratitis, Pekingese accounted for the majority, with 28 cases; next was the Lhasa Apso, with 15 cases; then small mixed-breed dogs, with 11 cases; in addition there were 5 Cocker Spaniels, 5 small hounds, 2 Pugs and 2 Pomeranians.
1.2 Causes
1.2.1 Trauma damage It is mostly seen in injuries caused by dogs biting each other, accidental kicks, collisions and scratches from dogs playing with each other. The cornea becomes inflamed after injury, and most of these cases are severe.
1.2.2 Foreign body irritation Sand and ash falling into the eye irritate the cornea; abnormal eyelashes irritate the cornea; sticky substances such as chewing gum adhering to the cornea irritate the cornea.
1.2.3 Drug factors Using expired eye drops or eye ointment to treat eye tearing causes corneal inflammation. Some also develop conjunctival and corneal inflammation after using an eye drop to which they are not suited.
1.2.4 Bacterial and viral infection Seen in canine distemper, infectious canine hepatitis, canine herpesvirus and Staphylococcus aureus infection. This situation is relatively common, and the condition is also relatively severe.
1.2.5 Unknown causes It may be caused by allergy or corneal nutritional imbalance.
2 Clinical symptoms
Among these 68 keratitis cases, unilateral eye involvement accounted for 36 cases, or 52.9%; bilateral eye involvement accounted for 32 cases, or 47.1%. Corneal opacity and neoplasm accounted for 34 cases, or 50.0%; corneal ulcer 23 cases, or 33.8%; corneal perforation 11 cases, or 16.2%.
The common symptoms of keratitis are photophobia and tearing, pain, conjunctival hyperemia and closed eyelids in the early stage, followed by corneal opacity, ulcer, serous or purulent eye discharge, and severe visual impairment. Traumatic keratitis shows corneal damage and bleeding, and in infected cases suppuration and ulceration. Canine distemper mostly involves both eyes at the same time; besides eye symptoms, systemic symptoms are also relatively obvious, such as depression, body temperature rising to 39.5°C-40.0°C, etc. Corneal opacity is an opaque white nebula formed on the corneal surface; the opacity may be localized or diffuse, and new corneal opacity has indistinct boundaries, a rough and raised surface, and inflammatory symptoms. Old corneal opacity has no inflammatory symptoms and distinct boundaries. Deep corneal opacity is mostly pale blue and cloud-like. Corneal neoplasm is obvious local proliferation and thickening of the cornea. Corneal ulcer is an irregular defect of the superficial or deep corneal layer. In corneal perforation, the cornea ruptures, and aqueous humor and viscous exudate flow out from the rupture, with even capillaries exposed. Corneal macula is an opaque grayish-white scar formed in the later stage of corneal opacity and ulcer.
3 Treatment
The principles are eliminating the cause, reducing inflammation and relieving pain, and promoting absorption, using a combination of local drug treatment and systemic treatment.
Flush the eyes with normal saline to remove foreign bodies and secretions in the eye. In the acute stage, when the cornea has not yet developed suppuration, ulceration or perforation, use chloramphenicol eye drops and cortisone acetate eye drops alternately, 3-5 times a day. At the same time carry out systemic treatment, with ampicillin sodium injection, compound aminopyrine injection and dexamethasone sodium phosphate injection by intramuscular or subcutaneous injection, 1-2 times a day for 2-7 consecutive days. For viral keratitis, use polyinosinic-polycytidylic acid injection or immune serum as appropriate, once a day or every other day, for 3-5 consecutive days. In addition, symptomatic treatment should be given, and when necessary, intravenous infusion of 5% glucose saline to improve systemic symptoms and increase the animal's resistance. If keratitis is secondarily infected with bacteria, with suppuration, ulceration or even perforation, use penicillin 80,000 units mixed with 0.5 ml of normal saline for eye drops, 3-5 times a day, while carrying out systemic treatment. If corneal perforation is severe, tarsoconjunctival flap surgery can be performed to make an autologous eye bandage for the affected eye, which can effectively stop the continued outflow of aqueous humor, prevent the invasion of pathogenic microorganisms, and help repair the corneal damage. Combined use of inosine, vitamin C, vitamin B1 and vitamin B2 gives better results. Strengthen nursing care of the sick dog, minimize its outdoor activities, avoid strong light stimulation and ash and sand falling into the eye, avoid rough play with other dogs that may injure the affected eye, and feed nutritious and easily digestible food.
4 Summary and experience
68 sick dogs were treated, 66 were cured, with a cure rate of 97.06%. 2 cases were not cured; one had already been treated elsewhere for many days when it was seen, with corneal ulceration and suppuration and lens prolapse, and became completely blind after the inflammation was eliminated; the other was traumatic keratitis with severe injury, and the owner gave up treatment after 3 days. For mild cases, systemic treatment for 1-2 days and local treatment for 3-5 days can cure the disease; for severe cases, systemic treatment for 3-7 days and local treatment for more than 7 days are needed for recovery; in cases of corneal ulcer and perforation, small round dot-like defects or grayish-white maculae often remain on the cornea after treatment, but they have little effect on vision.
When treating canine keratitis, the choice of eye drops is very important, because there are now many types of eye drops for human use, but not every one is suitable for dogs. Clinically it is common to see some owners only paying attention to buying expensive eye drops for treatment, but because the effect is poor, the condition is delayed. When treating canine keratitis, systemic adjuvant treatment is also very important, especially for those with severe systemic symptoms, in which systemic treatment should be the main approach. When treating keratitis of unknown cause, the author treats the eye disease on the one hand and clears retained feces from the intestines and changes the type of food on the other, which often achieves twice the result with half the effort, because such affected dogs often take meat, animal liver and other internal organs as their staple food, and develop eye disease due to nutritional imbalance or excessive liver fire. When treating canine eye disease, the author does not advocate using eye ointment, because the ointment is sticky, makes the dog uncomfortable, and causes it to keep scratching its eyes, aggravating the damage to the eye. However, using it once at night during sleep to prolong the duration of action is also acceptable.
The causes analyzed above are those commonly seen by the author in clinical practice, but among the 68 statistically analyzed keratitis cases diagnosed and treated, keratitis caused by canine distemper is not included, because the cure rate of canine distemper is low and the focus was placed on treating other conditions.
The causes of canine eye diseases such as corneal opacity and ulcer are complex, including external causes (physical, chemical and microbial), internal causes (allergy and nutrition) and some unknown causes. It has been reported abroad that one cause of corneal opacity is that collagenase produced by epithelial cells destroys the formation of collagen, and as a result light scattering through the cornea produces opacity; collagen is a very strong protein, and under normal pH conditions, apart from collagenase, collagen generally cannot be decomposed and destroyed. However, under the stimulation of microbial infection, physical and chemical factors and so on, large amounts of collagenase are produced in corneal epithelial cells, destroying collagen and causing corneal opacity and ulcer; 3% N-acetylcysteine eye drops have the characteristics of significant efficacy, safety, reliability and good stability in treating canine eye diseases, because 3% N-acetylcysteine eye drops can inhibit excessive collagenase activity in the early stage of inflammation, remove damaged cornea and help corneal regeneration, improve corneal ulcer, inhibit its development to depth, and promote the repair of corneal epithelial cells. In addition, there are domestic reports of using autologous blood to treat canine keratitis.