Abnormal size & Position of the eye Flashcards
problems with The Orbit and Space Occupying Lesions
Infection/infl (abscess/cellulitis)
Neoplasia (usually malignant)
Specific tissue infl
globe displacement clinical signs
often dorsolaterally
freq anterior component - Exophthalmos
why does the 3rd eyelid protrude with exophthalmos
mass displaces orbital fat which pushes on the 3rd eyelid
what is microphthalmia
small eye from birth
usually bilateral
may have other defects
cause of microphthalmia
destruction of ciliary body (cyclodestruction)
sequela to infl, pthisis bulbi (severe uveitis)
targeted surgical destruction
chemical ablation
what is buphthalmia
enlargement of the eye
buphthalmia is due to…
incr in IOP - glaucoma
buphthalmia - pathogenesis
incr IOP causes globe stretching + other changes
buphthalmia - effects on the eye
conjunctival + episcleral vessel hyperaemia
corneal oedema (endothelial damage)
Haabs strike (breaks in descemets membrane)
zonular tears
corneal ulceration - d/t corneal overexposure
zonular tears
over stretching of fibres d/t lens displacement
visible lens equator through pupil
glaucoma
incr IOP
damage to the optic nerve head + neural retina
the retina has how many layers
10 - 1 epithelial + 9 neural (rod + cones etc)
primary glaucoma
inherited - affects both eyes, don’t breed the animal
goniodysgenesis - abnormal iridocorneal angle (ICA)
2 forms of primary glaucoma + which affects dogs more
open + closed
closed is more common in dogs (rapid onset)
open more in humans (insidious onset)
secondary glaucoma
something affecting the ICA
causes of secondary glaucoma
blood, fibrin, PFIMs, WBCs, neoplasia infl hyphema lens luxation intraocular/metastatic neoplasia trauma
causes of feline glaucomas
can be primary
mostly secondary with uveitis - FIV, FeLV, FIP + toxoplasma, idiopathic
why consider the other, non affected eye in glaucoma
primary glaucoma will affect both eyes
long term monitoring of other eye is needed
glaucoma - clinical signs with mid to high IOP
mid-dilated non-responsive pupil
conjunctival + episcleral vess conjugation
+/- vision problems
glaucoma - clinical signs with high to v.high IOP
corneal oedema haabs striae cupping of optic nerve head lens displacement aphakic crescent
aphakic crescent
tear of the zonules + lens movement away from it
development of crescent between pupil + lens
(corneal ulceration)
glaucoma - treatment
control IOP - antihypertensive drops
if secondary - remove cause
phacodonesis
vibration on the lens
iridonesis
movement of the iris
when does phacodonesis + iridonesis often happen
often in early stage of subluxation
posterior luxation
lens falls backwards into the eye
cataract formation
lens induced uveitis
lens adheres to the retina
anterior luxation
lens moves forward into the anterior chamber
rare
anterior luxation - potential problem
pupil block glaucoma
corneal endothelial damage
damage to centre of the cornea
clinical signs of subluxation/luxation
iridonesis-phacodonesis
deep anterior chamber
anterior presentation of the luxation
incr IOP
what damage does rapid + high incr in IOP do
retinal ganglion cell
optic nerve head
(blood vessels)
main cause of rapid + high incr in IOP
pupil block glaucoma
treatment of pupil block glaucoma
immediate removal of the lens
medical therapy to control future IOP spikes
surgical management of lens luxation
remove lens prior to anterior luxation
remove lens if acutely luxated anteriorly
control of IOP with drugs
