Ocular, orbital and periorbital neoplastic conditions of the horse

Primary neoplasia of the ocular, orbital and adnexal structures of the horse are relatively common – this is however, simply because a few common types of neoplastic disease are frequently identified and are easy to see and examine. There are published case reports of neoplastic disorders for almost every ocular structure even though there are relatively few specific tumour types and some tumours can affect multiple structures. For example squamous cell carcinoma can affect the eyelids (palpebral carcinoma), the conjunctiva (conjunctival carcinoma) and the cornea (in situ carcinoma). Likewise, melanoma can occur in the eyelids [1], the iris (uveal melanoma) [2] and in the retina. The commoner adnexal and ocular tumours are shown in Table 1.