Ocular findings in cats with feline infectious peritonitis treated with GS-441524: a preliminary prospective study of 118 cases

Objectives: This study aims to characterise the presence and nature of ocular findings in cats diagnosed with feline infectious peritonitis (FIP) and to evaluate the effects of antiviral treatment with GS-441524 on ocular manifestations. Methods: Study participants were prospectively recruited over a 1-year period by the FIP study team at the Vetsuisse Faculty, University of Zurich. A total of 118 cats diagnosed with FIP underwent a comprehensive standardised semi-quantitative ophthalmic examination. Cats with ophthalmic abnormalities at the baseline examination received a follow-up examination on days 7 and 42, after commencement of the oral antiviral therapy, GS-441524. Changes throughout the treatment period were recorded and reviewed. Results: At the baseline examination, 48/118 (40.1%) cats had ocular abnormalities, with the most common associated findings being anterior uveitis, keratic precipitates and chorioretinitis. Throughout the course of treatment with GS-441524, significant improvements were observed in all ocular segments, with rapid improvement noted during the first 7 days of treatment in most cases. Residual chorioretinal lesions and vitreal cells persisted in a minority of cases. Conclusions and relevance: This study suggests that ocular abnormalities in cats with FIP are more common than previously reported. Potentially vision-threatening posterior segment changes occurred frequently, and treatment with oral GS-441524 led to rapid improvement in most ocular lesions, particularly uveitis and chorioretinitis. These findings support the inclusion of ophthalmic examination as part of the clinical evaluation of cats with suspected or diagnosed FIP.