This chapter provides a brief overview of ophthalmology. For more detailed ophthalmology notes, refer to The Colour Atlas and Text of Equine ophthalmology (Barnett et al, 1995).
As there is very little difference in ocular anatomy and disease between the horse and the donkey, the veterinary surgeon can follow the same approach to the examination of the horse's eye when dealing with the donkey. The examination must be thorough and methodical, with an emphasis on recording the history to decide a treatment regime and monitor response. However, more research needs to be done to understand the propensity for chronic ocular surface disease.
A particular feature of ophthalmic disease in equids is the serious consequence of inadequate initial treatment due, in part, to the character of their inflammatory response. Most of the differences between donkey and the horse are in their nature. Donkeys are more stoical, so may not present olular disease in its early stages because of their muted pain response. First examination may reveal a more severe or chronic problem. Sedation is less frequently needed because the reserved nature of the donkey aids examination and treatment. However their strong palpebral muscles make blocking the frontal nerve an essential part of examining a painful eye. Donkeys are generally very tolerant of nasolacrimal and subpalpebral lavage devices if these are required for treatment delivery.
Differences in occurrence of eye problems in the donkey may exist when compared to the horse. The more dynamic use of the horse makes it more prone to traumatic injuries to the eye. The donkey may be more prone to organic foreign bodies lodging in the eye, due to its habit of feeding with head buried into hay or straw, and in winter by its tendency to develop a think coat and hairy face. These differences may also present a seasonal variation in occurrence.