Mapping the Evidence for Bioactive Compound-Based Adjunctive Therapies in Canine Ocular Diseases: A Scoping Review

Bioactive compounds are widely used as adjunctive therapies for canine ocular disease, yet the supporting evidence has not been systematically mapped. This scoping review characterised its distribution, design and direction. PubMed and CAB Abstracts were searched, supplemented by Google Scholar and backward citation searching; 1350 records were screened and the 50 included studies were charted by compound class, disease category and study design. They addressed keratoconjunctivitis sicca; the cornea and ocular surface; cataracts and lenses; retinal disease; and glaucoma, the last with only a single study. Thirteen were therapeutic trials in dogs with naturally occurring disease, seven of them in keratoconjunctivitis sicca; eleven further studies used healthy or purpose-bred dogs or induced models. The remaining evidence rested mainly on in vitro work, deficiency observations and uncontrolled reports. Null or unfavourable results were reported for topical hyaluronic acid in corneal wound healing and for dietary docosahexaenoic acid in progressive rod-cone degeneration. Reports on one marketed supplement differed in direction; commercial interests were declared in some but not others, and their influence could not be determined. This evidence map delineates where canine research has accumulated and where it has not, providing a basis for prioritising controlled trials with concurrent safety assessment.