Abnormal size eye Flashcards
What diseases can affect the size of the globe?
small eye: microphtalmia
large eye: buphtalmia
red herrings: seeminglly smaller or larger eye
What can cause microphtalmia?
- maldevelopment
- phtisis bulbi: trauma causing atrophy
- red herring: enophtalmia: globe retracted within the orbital cavity
- red herring: anisocoria: different pupil sizes
What is phthisis bulbi?
atrophy of the globe due to trauma
What is enophtalmia?
globe retracted within the orbital cavity
reduced amount of retrobulbar fat, periocular/facial muscle atrophy due to pain
typical of elderly cats, weight loss, long-term use of steroids
What can cause buphtalmia?
- primary glaucoma (congenital and inherited)
- secondary glaucoma (intraocular tumour and chronic uveitis)
- red herring: exophtalmia: globe pushed forward due to orbital dz
- red herring: corneal disease or different coloured iris
What is exophtalmia?
globe pushed forward due to an orbital disease (abscess, mass)
What are signs that could indicate exophtalmia over buphtalmia?
scleral ahow
difficulty on retropulsion of globe
difficulty blinking over globe
checking lines perpendicular to the skull axis, the globe is protruded rostrally
When a dog has a dilated left pupil due to an anterior lens luxation, what medical tx is contraindicated?
prostaglandin analogues
ex: xalantan, travatan
leads to miosis behind lens and IOP increases
What could indicate an congenital microphtalmia in a puppy?
small palpebral fissure
periocular wetness
secondary nictitating membrane protrusion
What are the characteristics of primary inherited glaucoma?
angle closure glaucoma usually acute onset
increase in IOP
aqueous outflow obstruction (sheet of uveal tissue: pectinate ligament dysplasia)
neurodegenerative disease w/ death of retinal ganglion cells
When is glaucoma and emergency and why?
if IOP over 50mmHg for a few hours = irreversibly blind
What is a proptosed globe?
eyelids are trapped behing the globe equator of the globe
EMERGENCY
painful condition, more common in brachy.
What are negative prognostic indicators with an ocular proptosis?
rupture of two ore more extraocular muscles, could compromise the blood supply to the eye
hyphaema can indicate a retinal detachment or globe rupture
dolicocephalic breeds have worse prognosis than brachy
What is different about ocular proptosis in cats vs dogs?
in cats the orbital rim is all limited by bone
a lot of force needed to cause globe proptosis
orbital fractures and globe rupture is associated to ocular proptosis
higher risk of blinding the other eye secondary of pulling at the level of the optic chiasma
