Equine Ophthalmology: Recurrent Uveitis, Posterior Segment Disease Flashcards
Iris abnormalities:
Persistent Pupillary Membranes
- Remnants of embryonic vasculature
- Commonly found on iris surface
– Incidental finding - May attach to cornea or lens and cause focal opacity
Iris abnormalities:
Iris Hypoplasia
- Dark area of iris bulging forward
– Usually dorsal
– More common in blue eyes - Thinned iris stroma (can retroilluminate)
- Rule out neoplasia
Iris abnormalities:
Iris Neoplasia
- Melanoma most common
– Gray horses - Dark mass filling anterior chamber
- Use ultrasound to differentiate from cysts
- Treatment
– Typically benign
– Enucleate?
Iris abnormalities:
Iris or Corpora Nigra Cysts
- Locations
– Corpora nigra, pupil margin, free-floating - May enlarge over time
- Should transilluminate
- Rule out neoplasia
- Treatment
– Benign neglect
– If vision compromised can diode laser or aspirate
Uveitis =
Uveitis- clinical signs/exam findings
Uveitis- primary/acute/first episode
• Diagnostic tests
Equine Recurrent Uveitis
ERU Lesions -
Chorioretinitis
• Chronic inactive lesions
bullet-hole lesions can be incidental findings
ERU Stages
ERU Pathogenesis
General Uveitis Therapy
ERU Treatment
Glaucoma
- prevalence?
- causes?
Glaucoma Clinical Findings
- Elevated IOP
– Normal is 15-30 mm Hg - PLR deficits or fixed and dilated pupil
– May still be visual (menace response intact) - Buphthalmos
- Corneal changes
- corneal edema
- bottom left: diffuse corneal edema
- bottom right: haabs stria, breaks in descment’s membrane due to bupthalmos
- optic nerve changes
- color change in optic disk (will look very pale)
Glaucoma Treatment
latanoprost won’t work cause doesn’t decrease IOP as much as in other species
Cataracts
- prevalence
- causes
- Majority of equine cataracts are non-progressive
- Developmental (including congenital) or acquired
- Congenital may be associated with other abnormalities (e.g. microphthalmos, persistent embryonic vasculature)
- Developmental (including congenital) or acquired
Cataracts
- types
- treatment
- Inherited
- Belgian, Thoroughbred, QH
- Acquired cataracts
-
Secondary to uveitis (ERU)
- Commonly anterior capsular/subcapsular +/- synechiae
- Secondary to trauma
- Senile cataracts (horses >20 years)
- DDx nuclear sclerosis
-
Secondary to uveitis (ERU)
- Cataract surgery can be performed in horses
- Young foals are preferred
- NOT generally recommended for cataracts secondary to ERU
Posterior segment diseases
- Equine Motor Neuron Disease
- honey comb mosaic pattern
- patient doesn’t show any other signs
- Ischemic &Traumatic Optic Neuropathies
- Proliferative Optic Neuropathy
normal eye: salmon pink disk, tapetum on top
Equine Motor Neuron Disease
- Neurodegenerative condition
- Vitamin E deficiency
- Clinical signs/findings
- Severe weakness
- Muscle atrophy and fasciculations
- 50% of horses have fundic changes
- “Honeycomb mosaic” pattern of dark brown to yellow pigmentation (ceroid-lipofuscin in retinal pigment epithelium)
- No visual deficits
Ischemic & Traumatic Optic Neuropathies
- Ischemic: sudden hypoxemia of optic nerve
– Thromboembolic disease
– Acute hypovolemia
– Surgical occlusion of the carotid artery - Traumatic: blunt trauma to head
- Clinical signs
– Blind eye with normal optic nerve initially – papilledema, focal hemorrhages, hyperemia, accumulations of axoplasmic materials (white stuff in pics), eventual optic nerve degeneration - Limited treatment options, grave vision prognosis
Proliferative Optic Neuropathy
- White or gray “mass” protruding from optic disc into vitreous
– Histologically resembles schwannoma - Visual eye (incidental finding)
- Typically older horses (>15 years)
- Benign neglect
– DDx neoplasia
