Abnormal pupil Flashcards
What are the 2 systems that can cause an abnormal pupil?
opthalmic
neuro
What are the 4 ophthalmic locations causing abnormal pupils?
iris
lens
retina
miosis/mydriasis
What are the 2 neuro signs causing abnormal pupil?
miosis/mydriasis
visual/plr pathways
What si Iris coloboma?
abnormal development of the iris leaving a defect or hole in the iris
What is a peristent pupillary membrane?
delayed regression of fetal vascular tissue
iris to iris, iris to lens, iris to cornea
can cause abnormal pupil
What is a uveal cyst?
spherical cysts formed from uveal epithelium, usually free floating in anterior chamber
can burst and leave pigment on corneal endothelium
abnormal pupil
What is iris atrophy?
with age, iris tissue can become thin and dissapear = ragged pupil margin
What is posterior synechia?
with uveitis the iris can become sticky and adhere to the anterior lens capsule causing dyscoria, decreased/absent PLR, glaucoma
What is iris melanosis/melanoma?
darkening of iris, benign melanosis or malignant melanoma
can cause change in pupil shape, decreased PLR and glaucoma
How does anterior lens luxation change pupil shape?
anterior displacement of the lens can alter the pupil shape and means that pupil doesn’t constrict and dilate as normal
What is sudden acquired retinal degeneration syndrome SARDS?
presents as sudden onset blindness (1-2w hx)
represents sudden degeneration of the photoreceptors
no ophthalmic or neuro abnormalities (other than absent menace and plr)
fundus appears normal, electroretinogram testing reveals flat line
What is progressive retinal atrophy PRA?
inherited dz
photoreceptors degenerate
causes initial cCS of night blindness followed by full
fundoscopy reveals tapetal hyperreflectivity and blood vessel attenuation (atrophy)
What is optic nerve head hypoplasia/coloboma?
congenital malformation of optic nerve causing eye to be blind from birth
pre-chiasmal lesion
What is optic neuritis?
inflammation of optic nerve
manifests as blindness or reduced vision
optic nerve head is pink/haemorrhagic, swollen, can be peripapillary oedema/retinal detachment
What are the four signs of horner’s?
miosis
enophthalmos
third eyelid protrusion
ptosis
What are the causes of miosis that can affect pupil shape?
uveitis
horner’s
What are the causes of mydriasis affecting pupil shape?
glaucoma
dysautonomia
fear
central blindness
What is dysautonomia?
deregulation of autonomic nervous system
causes 3rd eyelid protrusion, decreased tear production, mydriasis, megaoesophagus, megacolon, atonic bladder
Why can fear cause mydriasis?
when stressed: hightened sympathetic stimulation = mydriasis that is not very responsive to bright light = reduced/absent plr
What is the optic chiasm?
Where the optic nerves of both eyes meet
What are the signs of a pre-chiasmal lesion of one side?
dilated pupil, absent direct plr and present indirect plr of the affected side
normal pupil, present direct plr, absent indirect plr of non-affected side
What are the signs of a chiasmal lesion?
pupils dilated at rest, bilateral absent direct plr, bilateral absent indirect plr
What are the signs of a focal optic tract lesion of one side?
both pupils will be normal size at rest, direct and indirect plrs present
What are the signs of an oculomotor nerve lesion of one side?
dilated pupil at rest of affected side
absent direct and indirect plr of affected side
What are the signs of a parasympathetic nucleus of CN3 lesion on one side?
dilated pupil at rest of affected side
absent direct and indirect plr of affected side
What tests would you perform on ophthalmic examination of a 1day hx of sudden onset blindness in a 5yo dog?
menace
plr direct and indirect
palpebral
distant direct ophthalmoscopy
examination with lights
funduscopy
If electroretinography shows a flatline in a sudden onset blindness dog what is it likely to be?
SARDS
What 3 things do we talk about when describing the retina?
tapetal reflectivity
retinal vasculature
optic nerve head
What happens to the retina structurally when there is hyperreflectivity?
retina is thinner than usual
can happen in progressive retinal atrophy (PRA)