SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
should be to provide the potential purchaser with a professional and considered
opinion to allow an informed decision on the purchase to be made. In most instances
it is possible to state that:
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Ocular abnormality is or is not present.
Abnormality will have either a significant effect or no significant effect on
functional vision.
The abnormality is either unlikely in its normal course to progress or might
progress over time.
The findings should be presented in a written report with / without annotated
diagrams along with an opinion on the effect of that finding on functional vision and
its anticipated progression or lack of progression in its normal course, and, if
possible, obtain a dated photographic record of the eye. It is not appropriate to make
quantitative statements about visual impairment (e.g. ‘this horse has 50% vision’),
nor to make subjective judgements, such as stating that a horse with an ocular
abnormality is suitable to be ridden only by a skilled rider in an outdoor or well-lit
environment.
A few general guidelines will go a long way to make the ocular PPE easier. These
include:
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Horse with congenital or long standing lesions are likely to have adapted to
any loss of disruption of visual input.
Any dense opacity along the visual axis may disrupt light reaching the retina
and interfere with binocular and high visual acuity or cause a blind spot. This
would include pathology on the cornea, in the anterior chamber, lens and
vitreous.
Retinal pathology affecting the visual streak in the region of 1-3 disc
diameters superior to the optic disc.
Any extensive peripapilliary pathology that has obvious attenuation of the
retinal blood vessels is likely to be affecting ganglion cells.
The examination:
Equipment required for the standard examination is a focal light source, direct
ophthalmoscope and some form of magnification could be an added bonus.
As an initial examination the horse can be observed outdoors under saddle if
required before being stabled and on first approach and subsequent handling of the
horse be attentive to behavior or other signs suggesting visual impairment. Examine
the horse’s head symmetry by standing in front and looking up the muzzle, check the
ocular and adnexal symmetry, ocular discharges or facial staining and the angulation
of the eyelashes. Lashes pointing downwards would suggest ocular discomfort.
Perform the direct and consensual pupil responses, distant direct ophthalmoscopy
and close up direct ophthalmoscopy. It’s best to perform the later examinations in a
darken stable. Most retinal pathology can be seen through a mid-dilated pupil which
can be achieved by a few minutes of dark stable adaptation but if one is unsure then
a short acting mydriatic [Mydriacyl, 1% tropicamide] can be used but it is not
considered essential for the PPE. Mydriasis would be required for complete
examination of the lens and ocular posterior segment. Response to a mydriatic also
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