SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
• They are considered traumatic in origin ( rather than being caused by equine recurrent uveitis ).
Areas of increased iris hyperpigmentation should be examined carefully . Thy could be related to uveitis or these could be nevi and may be inconsequential but larger areas that are more peripheral towards the iridocorneal angle may suggest a ciliary melanoma . This may require further investigation using ultrasound . Most iridociliary melanomas are seen in grey horses and they may show no growth once diagnosed or grow slowly but rarely metastasize . The local expansive nature may cause a leukoma or block the drainage angle or obstruct the pupil . Affected horses will always carry a risk of glaucoma and these animals should not be considered suitable for purchase .
Lens : Lens abnormalities also present the examiner with challenges . Retrolental opacities associated with developmental irregularities often are associated with some pigment deposit and are usually minor and hardly ever affect functional vision and alone should not affect the PPE . It is the observation of a cataract that is more complex . The examiner needs to try and establish exactly where in the lens the opacities are located . Developmental cataracts generally are non-progressive but those causing extensive and bilateral obstruction of the visual axis should be considered significant in the PPE . These horses ideally should not be used for breeding . In the case of acquired cataracts which have occurred secondary to injury or intraocular disease should show other signs of inflammatory injury . Acquired cataracts are potentially progressive and purchases should be advised against purchase . The presence of lens luxation is usually caused by trauma or inflammation and seldom does the luxation physically cause a visual problem but affected horses are not considered suitable for purchase .
Vitreous : Developmental vitreal opacities usually show no impairment of functional vision but the examiner needs to make an assessment if the “ floater ”, be it developmental or acquired , is affecting the visual axis and prevents adequate visualization of the fundus . Should this be the case then the horse is unsuitable for purchase . Acquired vitreal inclusions usually have signs of inflammatory cellular debris , old blood or vitreoretinal detachments . These could raise the suspicion of equine recurrent uveitis .
Optic Nerve : A horse presenting with unilateral optic nerve atrophy and leading to blindness in that eye is not considered suitable for purchase . It potentially could be related to an expansive mass in the chiasma . Other masses arising from the optic nerve such as astrocytomas and cases of proliferative optic neuropathy although usually show visual eyes each case would have to be assessed on its own merits regarding to the size of the lesion or any evidence of affecting vision .
Retina : There are many colour variations of the equine fundus , so careful examination is required . The equine fundus does not have large blood vessels like we see in the dog fundus so attention to detail of the fine blood vessel structure is important . In essence the indicators of fundic disease can include ; loss or attenuation of the peripapillary retinal blood vessels , areas of pigment dispersion or loss of pigment , white areas with increased scleral reflex , choroidal blood vessel changes , increased pigmentation in the tapetal region and retinal detachment . Areas
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