Sophie Hofmann‐Wellenhof (Department for Companion Animals and Horses, University of Veterinary Medicine Vienna, Vienna, Austria) Sophie Hofmann‐Wellenhof Barbara Nell (Department for Companion Animals and Horses, University of Veterinary Medicine Vienna, Vienna, Austria) Barbara Nell Wiley 2024 Purpose This study aims to inform about the clinical image, diagnostic possibilities, and treatment options for cats and dogs diagnosed with ocular encephalitozoonosis. Materials and Methods Medical records of 7 dogs and 75 cats with ocular encephalitozoonosis presented at the Clinical Unit of Ophthalmology of the University of Veterinary Medicine Vienna between 08/2006 and 02/2022 have been compiled. Diagnosis was based on the presence of cataracts and positive antibody titer against Encephalitozoon cuniculi. Patient history, details on the characteristics of the cataracts, level of antibody titers, and the treatment regimen were summarized, as are the results of histological stainings of surgical samples to determine the presence of Encephalitozoon cuniculi, as well as PCR analyses to identify its sub-strains. Results Our analysis of the clinical data shows that focal cortical anterior cataracts often associated with anterior uveitis and lesions in the fundus are the most prevalent manifestation of ocular encephalitozoonosis in cats and dogs. Conclusion Serological testing and PCR analysis of lens material are the most important diagnostic tools. Timely phacoemulsification with adjuvant anti-inflammatory and antiparasitic medication is the most promising therapy for Encephalitozoon cuniculi-induced cataracts. PDFDocument eng 2026-03-12T09:57:54.890588Z 2024 Canine Cataract Eye Feline Lens Microsporidia 2144312 b application/pdf http://creativecommons.org/licenses/by-nc-nd/4.0/