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Improving the diagnosis of canine keratoconjunctivitis sicca
  1. DJ Haeussler Jr
  1. The Animal Eye Institute, Cincinnati, OH, USA
  1. email: djhoyslur{at}

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Keratoconjunctivitis sicca (KCS) is a relatively common condition affecting dogs worldwide.1-3 KCS is characterised by a deficiency in the production of the aqueous portion of the tear film, leading to conjunctival hyperaemia, bacterial overgrowth, ocular discharge, corneal vascularisation, corneal pigmentation, ocular pain and loss of vision.4-6 The primary cause of KCS is immune-mediated, but many other causes have also been reported, including congenital, metabolic, infectious, drug-induced, neurogenic, radiation, iatrogenic and idiopathic.7

The diagnosis of KCS is based on the presence of consistent clinical signs and measurement of decreased aqueous tear production using the Schirmer tear test (STT).8 It is largely accepted that an STT value greater than 15 mm/minute is considered normal for dogs, 11 to 14 mm/minute indicates subclinical KCS, 6 to 10 mm/minute indicates mild KCS and 5 mm/minute or less indicates severe KCS. However, several authors have criticised the STT’s variable sensitivity and reproducibility for diagnosing mild KCS.9,10

Due to the variability of STT measurements, a definitive diagnosis for mild cases of KCS may be difficult with the STT alone. As such, there is currently much interest in alternative measures for the diagnosis of KCS.

A small number of previous studies …

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