Use of Ocular Ultrasound

Introduction
Ultrasonography can be used to examine the intraocular and retrobulbar structures in the standing horse. In a compliant animal, chemical restraint may not be necessary. However, conditions requiring further investigation using ultrasonography are often extremely painful such that sedation and possibly even regional anaesthesia is required.

Ultrasonography allows examination of the globe when there is opacity of the cornea, aqueous humour, lens or vitreous humour, or when there is extreme eyelid swelling preventing ophthalmic examination. In addition, it is useful in the further evaluation of intraocular masses or exophthamlus and for identifying foreign bodies. The most common indications are to evaluate for the presence of a retinal detachment after trauma, with uveitis and associated miosis to examine the posterior chamber, with hyphaema, when a cataract is present and with severe corneal opacities.

It is performed using ideally a 10 MHz transducer, but 5 or 7.5 MHz transducers will also produce good images. The transducer can be placed directly on the cornea or onto the closed eyelids. If the former method is used, a stand-off is required for examination of the anterior segment and topical local anaesthetic agents should be applied to the cornea. There are no set images that have to be obtained. The globes should be systematically examined in horizontal, vertical and oblique planes. [...]