Ocular Emergencies Flashcards
What nerves control movement of the globe?
- CN III, IV VI, and extraocular muscles, allowing 240 degree vision
MAP directly affects which part of the eye?
Aqueous humor
Pupil constriction is controlled by____
The PNS
Pupil dilation is controlled by ____
The SNS
In what order should routine ocular testing be performed?
STT –> Fluoroscein stain –> Tonometry
Why is triple antibiotic ointment (neo/poly/bac) not recommended in cats?
Due to reports of anaphylaxis
What is glaucoma?
A congenital disease in which there is a decrease in aqueous outflow, leading to an IOP >25mmHg. Increased pressures reduce blood supply to the retina and optic nerve, necessitating prompt tx to preserve vision
What breeds are predisposed to glaucoma?
- English/American cockers
- Siberians
- Toy poodles
- Bassets
Is glaucoma more common in dogs or cats?
Dogs; rarely cats
Are one or both eyes affected in glaucoma?
Bilateral disease, but often one eye is affected first
What is the most common cause of secondary glaucoma in dogs?
Lens induced uveitis secondary to cataract formation
What is the usual age of onset for glaucoma?
Dogs 4-10 years
At what IOP is mannitol indicated to shrink the vitreous humor?
40-60
What medications can be used for glaucoma?
- Carbonic anhydrase inhibitors (Drozolomide, Brinzolamide)
- Beta adrenergic antagonists (Timolol)
- Prostaglandin analogues (Lantanoprost; not effective in cat, contraindicated in lens luxation)
What tell tale sign is seen in uveitis?
Aqueous flare
Why does uveitis have low IOP?
Decreased IOP results from decreased aqueous production
Etiology of uvieitis
- Intraocular inflammation is initiated by local tissue injury
- Damaged tissue and microorganisms release tissue factors and inflammatory mediators that cause vasodilation and increased vascular permeability
What is iris bombe?
An accumulation of aqueous humor behind the iris causing it to billow forward
How is uveitis treated?
- Treat underlying cause
- Mydriatics to dilate pupil and relieve muscle spasms of iris and ciliary body
True or false: Anterior lens luxation is an emergency
True
True or false: Posterior lens luxation is an emergency
False
What breeds are predisposed to primary lens luxation?
- Terriers
- Border Collies
- Brittany Spaniels
- Aus cattle dogs
- Shar peis
Lantanoprost is contraindicated in _____?
Anterior lens luxation
Lens luxation can lead to what other problems?
Glaucoma due to obstruction of fluid outflow, and uveitis
The use of corticosteroids is contraindicated in ___?
Any case where the cornea is injured
What two signs are a favorable indication of function in proptosis?
- A consensual reflex in the unaffected eye
- A miotic pupil in the affected eye
What is hyphema?
- Blood collection in the anterior chamber of the globe
- Can lead to glaucoma due to fibrin collection not allowing drainage of aqeuous humor
What is one of the leading causes of incurable canine vision loss?
SARDS
What is SARDS?
- Characterized by acute onset of blindness due to loss of photoreceptor function
- Majority of dogs also show systemic abnormalities suggestive of hyperadrenocorticism
What breeds are predisposed to SARDS?
- Daschunds
- Chinese pug
- Min schnauzer
- Bichon
- Beagle
- Brittany
- Pom
What is progressive retinal atrophy?
- A congenital inherited photoreceptor dysplasia seen in many dogs
- Progresses slowly over years
- No effective treatment
What is retinal detachment?
- Separation of the retina from underlying choroid
- Anatomically, separation of the photoreceptor layer from the retinal pigment epithelial layer of retina
What are the 5 main types of retinal detachment?
- Serous detachment (accumulation of exudates or blood under retina)
- Traction band detachments (fibrous bands contract and pull retina off)
- Vitreous degeneration (liqueification of vitreous allows it to seep under retina)
- Congenital (not a true detachment - failure of embryonic layers to unite - seen in collie eye anomaly)
- Iatrogenic (after cataract surgery)
What does the presence of blood vessels in the cornea always indicate?
Ongoing corneal pathology
What is the leading cause of complicated corneal ulcers?
The use of topical steroid in a patient with a corneal defect
What demographic is prone to melting ulcers?
Brachycephalics
What is a melting ulcer?
The cornea is made of collagen and the ulcer produces a collagenase that eats through the cornea
How can melting ulcers be treated?
- Serum eye drops can stop collagenic activity
- NAC
What breed is more susceptible to KCS?
Burmese
What is pannus?
- The superficial vascularization of the cornea with infiltration of granulation tissue
- Immune mediated disease
What is corneal sequestrum?
- Occurs when an area of the cornea has become sequestered and dies
- Patient usually has a history of corneal injury
Surgical treatment of an ulcer is recommended when the depth of the ulcer is ____?
> 2/3 normal thickness
What is Horner’s?
- Oculosypathetic paresis
- Secondary to loss of sympathetic innervation to the eye
What signs are seen in Horner’s?
- Ptosis
- Miosis
- 3rd eyelid protrusion
- Enophthalmos
What are the two classifications of Horner’s?
- Preganglionic: interruption of the nerve between spinal cord and synapse in ganglion
- Trauma, head/neck surgery, brachial plexus injury, intracranial or thoracic neoplasia
- Postganglionic; nerve has been interrupted between synapse and eye itself
- Otitis media/interna, idiopathic
Approximately what % of Horner’s in dogs is idiopathic?
50%
What medication can be utilized to localise a causative lesion of Horner’s?
- Phenylephrine, an alpha 1 adrenergic agonist
- If lesion is postgalionic, ocular signs will resolve within 5 minutes
- If lesion is preganglionic, signs will NOT resolve quickly
What is buphthalmos?
Enlargement of the globe
What is panophthalmitis?
Inflammation of all structures or tissues of the eye
What is epiphora?
Watery eyes
What is melbomian gland abscess/adenoma (chalazion)?
The chronic or acute swelling of one or more melbomian glands along the upper and lower eyelids
What is symblepharon?
The adhesion of the conjunctiva to the lid and eyeball that occurs in utero
