Today's Veterinary Practice

JUL-AUG 2014

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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July/August 2014 Today's Veterinary Practice 17 DiagNOSiS & TReaTMeNT OF KeRaTOCONjUNCTiViTiS SiCCa iN DOgS | Chronic surface irritation results in: • Conjunctival hyperemia • Squamous metaplasia of the surface epithelium • Hyperkeratinization of the surface epithelium • Thickening of the corneal epithelium. Inflammatory cells and blood vessels enter the anterior corneal stroma, depositing pigment, lip- ids, and calcium. The vascularization and deposits stabilize the cornea and make it less susceptible to ulceration; however, their presence can result in vision loss. TabLe 2. Causes of Quantitative KCS cAUSe PATHOGeNeSIS PreDISPOSITION DUrATION PrOGNOSIS a Disease (Ophthalmic) Chronic severe conjunctivitis Swelling of excretory ductules of lacrimal gland None Variable: Permanent if scarring present Good immune-mediated lacrimal adenitis (primary KCS) immune-mediated destruction of lacrimal tissue with secondary atrophy 7 Most common cause of canine KCS b Lifelong Good Disease (Other) Canine distemper virus 8 Lacrimal adenitis Unvaccinated animals Variable: Many spontaneously recover Good to fair: if systemic disease survived, many recover idiopathic neurogenic 9 idiopathic: Present with ipsilateral dry nose Middle-aged female dogs Variable Good to fair: Some spontaneously resolve Leishmaniasis 10 Lacrimal adenitis, especially surrounding lacrimal gland ducts, where amastigotes accumulate animals in Mediterranean region or with travel history Variable Fair Hereditary Congenital alacrima Developmental absence of lacrimal tissue Yorkshire terrier overrepresented 11 Permanent; present at birth Poor: Often requires surgery medication etodolac 12 Nitrogen-containing pyrimidine/pyridine rings have direct toxic effect on lacrimal acinar cells None Variable Fair: if etodolac administration < 6 months, more likely to recover Sulfa-derivative medications 13 & related compounds 14 Nitrogen-containing pyrimidine/pyridine rings have direct toxic effect on lacrimal acinar cells Typical onset within 30 days of medication initiation 5 Variable: May resolve in 45–60 days or sometimes lifelong Fair: Discontinue medication immediately after decrease in STT Treatment/Trauma iatrogenic: Removal of third eyelid gland May decrease tear production and TbUT 15 None: History of removal of gland Variable Fair Local radiation therapy 16 acute adverse effect of radiation exposure None Variable: Dose dependent and patient sensitivity Fair Trauma to lacrimal gland or nerves 9 Decreased production/ distribution of PTF due to decreased blinking and/ or increased evaporation secondary to lagophthalmia 17 None Variable Fair to poor a. Based on initiation of medical management b. Many breeds are predisposed to primary KCS, including, but not limited to, the American cocker spaniel, cavalier King Charles spaniel, West Highland white terrier, and brachycephalic breeds (eg, English bulldog) 18 QUANTITATIVe KcS causes Causes of quantitative KCS—organized by type of cause—are listed in Table 2. The most common cause is immune-mediated lacrimal adenitis. Transient decreases in tear production can be iatrogenically caused by: • General anesthesia: Significantly decreases tear production for up to 24 H 4 • Xylazine, medetomidine, and butorphanol: Significantly decrease tear production temporarily 5,6 • Topical or systemic atropine: Causes secondary decrease in tear production that is not clinically significant in most dogs.

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