Dry Eye (Keratoconjunctivitis Sicca/KCS) Condition in Dogs: Causes and Treatment Options
Dr Akshay Kumar1, Dr Deeksha Bharti2
- Division of Surgery and Radiology, ICAR-IVRI, Izzatnagar (UP), 243122
- Division of Medicine, GBPUA&T, Pantnagar (UK), 263145
Dry eye disease technically called as Keratoconjunctivitis Sicca (KCS) is a chronic ophthalmic condition in which the quantity of tear production reduces from the normal physiological tears production. The deficiency of the aqueous portion of the tear film predisposes the ocular surface to infection. KCS can be divided into two types: the symptoms of one consists of decreased tear production or inadequate secretion of tears, and the symptoms of the other includes excessive tear evaporation, which is typical of brachycephalic breeds. Tears produced by lacrimal and accessory glands coat the outer surface of the eye hence are important to the overall health of eyes and vision. Tears also act as interface between the air and tissue for oxygen transport to the cornea.
Causes
There are several known causes of KCS in dogs, including:
- Immune mediated
- Systemic infection (canine distemper etc)
- Drug induced (sulpha group of drugs)
- Hypothyroidism
- Neurogenic Kcs
- Congenital
- Radiation
- Iatrogenic
- Idiopathic
Keratoconjunctivitis sicca (KCS) is seen in number of breeds of dog and is generally considered to have an immunological, and probably an autoimmune aetiopathogenesis
Symptoms
KCS is a pathology of the lacrimal apparatus. KCS can be divided into two types: the symptoms of one consists of decreased tear production or inadequate secretion of tears, and the symptoms of the other includes excessive tear evaporation, which is typical of brachycephalic breeds. This condition causes damage to the inter-palpebral ocular surface and is associated with symptoms of ocular discomfort. The reduction in tear production causes corneal inflammation, and in very severe cases, it can cause a permanent harm or even blindness. The key signs of canine KCS are dull lustreless ocular surface and importantly a penlight reflection that does not have a sharp boundary but broken up into many small individual reflections. Inflammation is an integral part of all moderate and severe dry eye diseases. KCS appears as a common conjunctivitis or as a mucopurulent one. As the disease becomes chronic, KCS manifests corneal vascularization, fibrosis, pigmentation, and recurrent corneal ulceration. Blindness or even loss of the eye may result from dense corneal opacification or corneal perforation secondary to deep ulceration.
Diagnosis
Diagnosis is based on medical history, clinical signs, and decreased tear production tests. The most common tear production test is the Schirmer tear test (STT) (Fig 1). Normal STT reading for one minute is more than 15mm, if it is between 10-15 mm/min then it is mild dry eye, if between 5-10 mm/min then it is moderate KCS and less than 5 mm/min is severe form of dry eye disease that can also result in ulceration of cornea due to dryness. Additional diagnostic tests that may be performed include corneal staining to check for corneal ulcers, intraocular pressure (IOP) to determine if glaucoma is present and tear duct examination or flushing to ensure normal tear drainage.
Treatment
Medical therapy aims to eliminate the cause when possible, to reactivate the tear film, to stimulate tears, to control and prevent secondary bacterial infections, and to reduce inflammation. Generally treatment of KCS includes use of
- artificial tear drops (carboxymethyl cellulose) (Fig. 2)
- acetylcysteine
- antibiotics
- corticosteroids
- pilocarpine
- lacrimostimulant agents
- Cyclosporine (CsA) has potent immunosuppressive properties, reflecting its ability to block the transcription of cytokine genes in activated T-cells. CsA also enhances mucin production from conjunctival goblet cells and found beneficial in enhancing tear film stability by increasing the tear production.
- Tacrolimus has a similar, but more potent, mechanism of action than CsA. Patients unresponsive to CsA may respond to tacrolimus treatment. Tacrolimus (0.1%) in KCS affected dogs prevent the progression of corneal pigmentation.
- Nerve growth factors
Fig: 1. Schirmer tear test (STT) Fig: 2. Artificial tear
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