This lecture will explore the diagnosis and treatment of most common causes of the ‘red eye’ in our small animal patients. The ‘red eye’ can be caused by multiple possible extra- and intraocular infectious or inflammatory diseases. It is important to perform a complete ophthalmic examination on each patient, which includes an examination of the adnexa, anterior and posterior segments. Basic ophthalmic tests for ‘the red eye’ include fluorescein stain examination for corneal ulcerations, Schirmer tear test (STT) measurement of tear production to evaluate for keratoconjunctivitis sicca (KCS – dry eye), and tonometry to measure the intraocular pressure to differentiate glaucoma versus uveitis. Systematic ophthalmic examination and testing will facilitate accurate diagnosis and treatment with optimal clinical outcomes for your patients.