Vet360 Vet360 Vol 05 Issue 03 - Page 14

OPTHALMOLOGY Keratoconjunctivitis Sicca (KCS): Common and Underdiagnosed Dr Ramona Allen BSc (Med) Hons BVSc MMedVet (Ophthalmology Resident) Johannesburg Animal Eye Hospital Tears are needed to lubricate the cornea, and remove debris and pathogens which may cause harm. Additionally tears function to nourish with oxygen, glucose, electrolytes, cleanse, lubricate, and maintain corneal clarity and protect with immunoglobulins, enzymes, anti-bacterial, growth factors and fibronectin. Changes in any of the above may lead to discomfort, infection, poor wound healing, visual abnormalities, and adjacent tissue dysfunction of the conjunctiva and eyelids. Normal tear film distribution relies on normal anatomy, normal tear film quality, and normal tear film quantity. The tear film is composed of lipid, mucin and water. A deficiency in the aqueous layer is referred to as quantitative KCS, whereas a lipid or mucin deficiency is termed qualitative KCS. Any condition which limits the production of any of these components has the ability to result in “dry eye”. Traditionally, dry eye was always considered a deficiency of the aqueous layer of the tear film, however more recently the definition of dry eye disease has been updated by the Dry Eye Workshop II (2017) and is described as, “ … a multifactorial disease of the ocular surface characterised by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyper-osmolarity, ocular surface inflammation and damage, and neurosensory abnormalities play etiological roles.” Eyes affected with KCS are generally red and painful, and the condition can be uni- or bilateral. Concurrent corneal ulcers and conjunctivitis may be present. Chronic, untreated KCS may can result in scarring, neovascularisation and pigmentation and, if severe, decreased vision. Causes of KCS are numerous but can be classified aetiologically: • • • • • • • • Sounds complicated, right? Well it is! The most common clinical signs seen with KCS include: Mucoid discharge, hyperaemia, neovascularisation, blepharospasm, epiphora, and a dull lacklustre cornea vet360 Issue 03 | JULY 2018 | 14 • Congenital Senile atrophy Immune-mediated - - Local - - Systemic e.g. Sjögren’s syndrome, systemic lupus erythematosus, pemphigus foliaceus, rheumatoid arthritis, polymyositis and polyarthritis, atopy, glomerulonephritis, and ulcerative colitis Infectious - - Canine Distemper Virus - - Viral or bacterial conjunctivitis - - Feline Herpes Virus Endocrine Disease - - Diabetes Mellitus - - Cushings Disease - - Hypothyroidism Irradiation Neurogenic Iatrogenic - - removal of the gland of the third eyelid - - uncorrected prolapsed gland of the third eyelid ("cherry eye") - - Facial nerve damage e.g. after total ear canal ablation surgery Breed-related - - American cocker spaniel - - Bloodhound - - Boston terrier