More than meets the horse’s eye: An insight into equine ophthalmology

The prevalence of ophthalmic abnormalities in horses is high, higher even than most people are aware of and this is why equine ophthalmology has increasingly become a focus of attention. Loss or impairment of vision of horses has negative consequences for performance, usability and welfare. This thesis comprises work that arose from research questions related to clinical (eye)problems encountered in daily equine practice and is divided in 3 parts. The first part is focused on unravelling of a genetic ophthalmic disease in the horse, namely distichiasis. In distichiasis, extra eyelashes grow from the tarsal glands on the eyelids. The treatment, long-term follow-up and the identification of the genomic regions associated with distichiasis have been described. Aspects of pharmacokinetics of corticosteroids, one of the most commonly used anti-inflammatories for the equine eye, have been addressed in the second part. The distribution into the different compartments of the equine eye of corticosteroid eye drops (dexamethasone and prednisolone) and oral corticosteroids (prednisolone) have been investigated. The third part focuses on anaesthesia, improving local anaesthetic techniques and adequate analgesia during and after (standing) surgical ophthalmic procedures in horses. This thesis sheds light on the genetic cause of an important ophthalmic disease like distichiasis in the horse, helps to improve evidence-based medical and surgical treatment, and provides a vision for further research and future perspectives for prevention and treatment of diseases of the equine eye.