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July/August 2014 Today's Veterinary Practice 19 DiagNOSiS & TReaTMeNT OF KeRaTOCONjUNCTiViTiS SiCCa iN DOgS | tvpjournal.com 3. A normal TBUT is ≥ 20 seconds. Animals with quanti- tative deficiencies often have a TBUT of < 5 seconds, which indicates an unstable PTF. 20 • Conjunctival Biopsy: In cases of suspected mucin defi- ciency, obtain a conjunctival biopsy specimen to quanti- tate conjunctival goblet cell density. • Eyelid Margin Examination: With a focus light and magnifying source, carefully examine the eyelid margin to identify deficiencies of the lipid component, which often occur secondary to blepharitis (Figure 6) or mei- bomianitis. meDIcAL mANAGemeNT OF KcS Primary medical therapy of both quantitative and qualita- tive KCS consists of tear stimulants and tear replacements. Topical antibiotics and anti-inflammatory drugs are also commonly used. Dogs with KCS may have increased sensitivity to pain associated with topical medications, because abnormal PTF cannot provide a reflex dilution effect. This may be espe- cially problematic with frequent application of tear replace- ment medications that contain preservatives; some artificial tear products are available without preservatives, but the lack of preservatives requires single-use ampules, which most owners find inconvenient. In most patients with KCS, topical therapy is required indefinitely. Clients should be educated about the chronic- ity of KCS and the necessity of lifelong therapy. Tear Stimulation 1. Cyclosporine A (CsA) Mechanism of action. Cyclosporine is an immunomodu- lator that blocks normal production of interleukin-2, which inhibits proliferation of T-helper and cytotoxic T cells in the lacrimal gland and allows normal lacrimation. 21 Cyclosporine also acts as an anti-inflammatory, decreases pigmentation, normalizes goblet cell mucin secretion, 22 and directly stimulates lacrimation, but the latter mechanism is still poorly understood. 23 Efficacy. Topical preparations are very effective for tear stimulation and reducing inflammation, with 81.8% of dogs showing improvement (Figure 7, page 20). 24,25 Dogs with a STT < 2 mm/min respond with increased tear secretion in approximately 50% of cases, while dogs with a STT ≥ 2 mm/ min have an approximately 80% chance of responding. 18 Formulation. CsA is available as Optimmune 0.2% oph- thalmic ointment (merck-animal-health-usa.com). Com- pounded formulations are available in 1% and 2% corn or Figure 6. Four-year-old castrated male Chihuahua with acute blepharitis. Figure 5. Diagnostic algorithm for dogs presented with clinical signs of keratitis.