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Disorders of eyes and vision
- Author: Jacques Penderis
- From: BSAVA Manual of Canine and Feline Neurology
- Item: Chapter 10, pp 167 - 194
- DOI: 10.22233/9781910443125.10
- Copyright: © 2013 British Small Animal Veterinary Association
- Publication Date: January 2013
Abstract
The neuro-ophthalmological examination combines aspects of the neurological examination and ophthalmic assessment in order to identify ophthalmic disorders arising from diseases affecting the nervous system. This chapters covers neuro-ophthalmological assessment, neuro-ophthalmic syndromes.
Disorders of eyes and vision, Page 1 of 1
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Central vestibular disease
(a) Head and body tilt. Adult miniature Dachshund demonstrating a left head tilt, and left truncal deviation on being held. The dog also prefers to lie with the left side down and becomes distressed when held with the left side uppermost. Testing of the righting reflex (when a dog is held horizontally the normal response is to reach upwards or right itself). The righting reflex is lost when the dog is held with the left side down. These combination of clinical signs indicate left vestibular syndrome.
Central vestibular disease
(b) Proprioceptive placing. Testing of proprioceptive placing using tactile placing response testing. There is loss of tactile placing in the left thoracic and pelvic limbs. When combined with the left vestibular syndrome in the previous video clip this is indicative of central left vestibular syndrome.
Central vestibular disease
(c) Strabismus. Ventrolateral strabismus of the left eye indicative of left vestibular syndrome. The strabismus becomes more obvious if the head is moved from the left head tilt position to horizontal. There is also an intermittent pathological vertical nystagmus, but this is less obvious on the basis of the video clip.
Central vestibular disease
(d) Sensory testing. Loss of sensation of the inner nasal mucosa suggestive of a lesion affecting the ophthalmic branch of the trigeminal nerve (the ophthalmic branch innervates the nasal mucosa, while the nasal planum is innervated by the maxillary branch of the trigeminal nerve). The dog also demonstrates a fluorescein-positive corneal ulcer within the central region of the cornea with no evidence of a painful eye, which is also consistent with damage to the ophthalmic branch of the trigeminal nerve. The presence of a left trigeminal nerve lesion in addition to the left vestibular syndrome is further evidence of a central left vestibular lesion. (See page 188 in the Manual)
Electroretinography
Electroretinography can be performed under general anaesthesia, or under sedation in a cooperative patient. A corneal contact lens electrode is used to record retinal voltage changes that occur in response to a defined flash of light or repeated flashes of light. The response is expressed as a waveform. (See page 174 in the Manual)
Pendular nystagmus
Albino and imperfect albino animals (including Siamese, Birman and Himalayan cats) demonstrate congenital disorganization of the retina and visual pathways. The consequent clinical anomalies seen in Siamese and related breeds include convergent strabismus (esotropia) and occasionally spontaneous pendular nystagmus. Pendular nystagmus is characterized as a spontaneous horizontal nystagmus with an equal velocity of eye movements in both directions (i.e. not a jerk nystagmus). (See page 187 in the Manual)