VN October 2021

Vetnuus | Oktober 2021 34 Regulars I Ophthalmology Column In the previous issue, we discussed the etiology of aqueous deficiency of the precorneal tear film [PTF]. In this issue, we will be looking at the clinical signs and diagnosis and discussing some of the treatment options. The clinical signs of KCS depend on whether the condition is bilateral or unilateral and acute or chronic. The hallmark feature of KCS is a mucoid/ mucopurulent discharge. The discharge is often not only the result of a decreased aqueous portion of the PTF but also increased mucin production by the conjunctival goblet cells. Other clinical signs include: • Dried discharge often presents on the eyelids. • Conjunctival hyperemia. • Blepharospasm and protrusion of the third eyelid may occur. • Corneal ulceration may occur. • Corneal vascularization [superficial]. • Pigmentary keratitis. • Dry Ipsilateral nostril. The nares may also be dry on the affected side, especially in neurogenic KCS. Diagnosis The clinical signs are very suggestive; a Schirmer tear test [STT] should be done on all patients with a mucoid ocular discharge, ulcerative keratitis or keratoconjunctivitis without any other apparent cause. STT values less than 15 mm/min are suspicious for KCS, and less than 10 mm/min are definite KCS. Patients with corneal erosions/ulcers should have an increased STT; in other words, in these patients, an STT of 10 – 15 mm/min is most likely KCS. Positive Rose Bengal stain. Rose bengal stains devitalized conjunctival and corneal cells. Treatment [Medical]: Most cases will respond to medical treatment; however, this will usually require lifelong treatment. Poor owner compliance or low patient acceptance of therapy is the primary cause of visual impairment in KCS. The eye must be cleaned before applying medication. Treating an eye caked with discharge is almost invariably ineffective. Cleaning the eyes is best done with water and gently wiping the eyes with soft gauze or tissue. The aims of medical therapy are: • Stimulate natural tear production. • The replacement of the precorneal tear film: this is essential in the early stages of KCS until natural tear production is expected. • Reduce ocular surface inflammation. • Control secondary infection. • Removal of excess mucous. Stimulation of normal tear secretion. Tacrolimus and Cyclosporin A are potent immunomodulators. Tacrolimus 0.02% applied twice daily is highly effective at improving tear production. Histopathology has shown that cyclosporine medication causes regeneration and duplication of atrophic acini. Tacrolimus and Cyclosporine take about 4-6 weeks to take full effect, and the increased tear flow can be monitored by performing regular STT’s. Both tacrolimus and Cyclosporine must be Pilocarpine is a parasympathomimetic drug that may stimulate lacrimal gland secretion. Pilocarpine can be administered either topically or systemically and are used in selected cases to stimulate tear production. It is used topically in a dilute form in artificial tears (0.125% or 0.25%) given every 8 hours or orally by being mixed with the animal’s food. The dose for oral Pilocarpine is initially one drop of 2% topical pilocarpine per 10 kg of body weight twice daily. The dose is increased in 1-drop increments every 2 to 3 days until tearing increases, or signs of systemic toxicity develop (inappetence, hypersalivation, vomiting, diarrhoea, bradycardia). The author reserves the use of Pilocarpine for suspected neurogenic KCS patients. Usually unilateral KCS with the ipsilateral dry nostril. v Dr Izak Venter, Digital Veterinary Ophthalmology Services (DVOS) Keratoconjunctivitis sicca [Part 4] The first mission of DVOS is to create a platform for the general practitioner veterinary surgeon to improve their ophthalmological knowledge and enable them to deal with ocular cases with more confidence. This will be done with online courses allowing participants to download course material that will include written notes as well as narrated PowerPoint presentations. The first small animal course comprises of 240 pages and the PowerPoint lectures are 20 hours in total excluding a guest lecture on SARDS. I shall alsomake surgical videos available covering some common surgical procedures. The course is CPD accredited with the South African Veterinary council for a total of 23 CPD points. The second mission is to provide a service to the practicing veterinarian offering specialist advice regarding problematic cases. More information regarding both of these aims are available on the website: www.dvos.co.za Figure 1. Typical appearance of a canine eye with keratoconjunctivitis sicca. Note the severe mucoid discharge.