Unit 2 - The fundus Flashcards
What are the components of the fundus?
Retina, retinal pigmented epithelium, tapetum, chroid, sclera, and optic nerve head
How do you evaluate the fundus?
Direct/indirect ophthalmoscopy
Ultrasonography
Electroretinogram
Advanced ocular imaging
What are the retinal vascular patterns?
Holangiotic, paurangiotic, merangiotic, and anangiotic
Describe the holangiotic retinal vascular pattern.
Vessels go throughout the fundus
What species have the holangiotic retinal vascular pattern?
Dog, cat, and rodent
Describe the paurangiotic retinal vascular pattern.
Short vessels directly adjacent to the optic nerve head
What species have paurangiotic retinal vascular patterns?
Horse
Describe the merangiotic retinal vascular pattern.
Vessels are in a broad horizontal band
What species have merangiotic retinal vascular patterns?
Rabbit
Describe the anangiotic retinal vascular pattern.
No blood vessels are in the retina
What species have anangiotic retinal vascular patterns?
Birds
What does the normal feline fundus look like?
Dark, small, round optic nerve - not myelinated
3 major venules leave the disk edge with 3 major arterioles
If the tapetum is present, it is usually yellow or green in color +/- pigment in the choroid
What does the normal canine fundus look like?
Usually 3 or 4 major venules that cross the disc edge
Forms a circle on the optic disc surface
Up to 20 arterioles
The tapetum can be any color
What does the canine optic disc typically look like?
Variable amount of myelin
Pale pink in color
Physiological pit +/- pigmented ring
What does the normal horse fundus look like?
30-60 small blood vessels extend a short distance from the disk edge
Oval, pink, optic disc in the non-tapetum
‘Stars of winslow’ - end on capillaries in tapetum
T/F: The pecten is a normal part of the rabbit fundus.
False - it is a normal part of the bird fundus
What are the clinical signs of fundic disease?
Vision-loss (day versus night)
Dilated, poorly/non-responsive pupils
Decreased/absent dazzle reflex
Changed tapetal reflectivity
Which of these is normal?
A - notice the hyperreflextive ring
Which of the following is representative of hyporeflectivity? Hyperreflectivity?
Hyporeflectivity - B
Hyperreflectivity - C
When a fundus is hyporeflective, what is the problem layer?
What is wrong with it?
Retina - edematous/infilatrated retina
When a fundus is hyperreflective, what is the problem layer?
What is wrong with it?
Retina - atrophy
What does vascular attenuation look like?
There should be tertiary branching and it should reach the periphery of the fundus
What disorders is vascular attenuation seen in?
Retinal degeneration
What vascular change is present in this photo?
Lipemia retinalis - hyperlipidemia
What vascular change is present in this photo?
Engorged vessels - hyperviscosity syndrome
What vascular change is present in this photo?
Perivascular cuffing - inflammatory disease
What vascular changes are present in these photos?
Retinal hemorrhages
What are the differential diagnoses for retinal hemorrhages?
Systemic hypertension
Coagulopathies
Chorioretinitis
Diabetic retinopathy (dogs)
Vasculitis
Severe anemia
Hyperviscosity
Trauma
What lesion is present in this photo?
Multifocal retinal dysplasia/folds
What lesion is present in this photo?
Multifocal retinal dysplasia/folds
What lesion is present in this photo?
Geographic retinal dysplasia
What is Collie Eye anomaly?
A hereditary eye disease in collies and other herding breeds
What syndrome does Collie eye anomaly cause?
Choroidal hypoplasia
Tortuous vessels
Optic nerve/peripapillary colobomas +/- retinal detachment
What is a coloboma?
Congenital defect/absence of tissue
What is optic nerve hypoplasia?
When there is a small optic nerve head with visual deficits
What breed is predisposed to optic nerve hypoplasia?
Miniature poodle
What is micropapilla?
A small optic nerve heat but visual
T/F: Progressive retinal atrophy is an acquired disease.
False - it is hereditary
What is progressive retinal atrophy?
The progressive loss of rods then cones
T/F: Progressive retinal atrophy is irreversible and there is no treatment.
true
How is progressive retinal atrophy prevented?
Genetic testing - avoid breeding
How is progressive retinal atrophy diagnosed?
History, fundic exam, genetic testing, +/- ERG
T/F: Cats don’t get progressive retinal atrophy.
False - they do, but it is less common
What signs on a fundic exam are indicative of progressive retinal atrophy?
Tapetal hyperreflectivity
Pale ONH
Blood vessel attenuation
How do patients with hypertensive chorioretinopathy typically present?
They often present for acute blindness
What ocular signs are associated with hypertensive chorioretinopathy?
Dilated, poorly to unresponsive pupils
Retinal detachment with retinal and vitreal hemorrhages
Do dogs or cats get hypertensive chorioretinopathy more?
Cats >> dogs
How is hypertensive chorioretinopathy treated?
Identify and treat the underling cauase
Calcium channel blockers - amlodipine primary therapy +/- ACE -inhibitor
T/F: Hypertensive chorioretinopathy patients can regain vision.
True - if the retina can reattach as soon as possible
What are the most common differentials for retinal detachment?
Hypertensive chorioretinopathy (esp cats)
Chorioretinitis
Congenital lesions
Post-intraocular surgery
How do you diagnose retinal detachment if you can’t visualize it?
Ocular ultrasound
What does retinal detachment look like on ocular ultrasound?
Classic seagull wing appearance
Usually remains attached at ora ciliaris and optic nerve
Hyperechoic lines traced to optic nerve
What is the cause of taurine retinopathy?
Chronic taurine deficiency in cats
What is taurine retionopathy?
Feline central retinal degeneration
How is taurine retinopathy confirmed?
Measure plasma taurine levels
T/F: Correction of a cats taurine deficiency will prevent progression of taurine retinopathy and will reverse it.
False - it will prevent progression, but won’t reverse it
In what species is enrofloxacin retinal toxicity found?
Cats
What dose of enrofloxacin results in retinal toxicity?
>5 mg/kg PO SID
What is the first sign of enrofloxacin retinal toxicity?
Dilated pupils due to retinal degeneration
If you have a patient that you suspect has enrofloxacin retinal toxicity, what should you do first?
Place them in the dark - light is what is associated with the damage
What should be used to treat enrofloxacin retinal toxicity?
Pradofloxacin
What species are most susceptible to ivermectin toxicity? Why?
Dogs are more susceptible to cats because they are scavengers and eat what they find
What dogs are especially susceptible to ivermectin toxicity?
Neonates and those with the MDR1 mutation
What clinical signs are associated with ivermectin toxicity?
Acute blindness, pupil changes, neurologic signs
What fundic changes are associated with ivermectin toxicity?
Retinal folds and edema
How is ivermectin toxicity treated?
Supportive care +/- lipid emulsion
T/F: Blindness due to ivermectin toxicity is usually transient and will reverse once the toxin leaves the system.
True
What can cause chorioretinitis (non-specific)?
Infectious, neoplastic, and immune-mediated/inflammatory causes
How is chorioretinitiis treated?
Treat underlying cause Symptomatic treatment of the chorioretinal inflammation
Why don’t you want to use anti-inflammatory eye drops to treat chorioretinitis?
The drops won’t reach the back of the eye
What does active chorioretinitis look like?
Indistinct borders and hyporeflective
What does inactive chorioretinitis look like?
Hyperreflective, well-demarcated, pigmented centers
What does SARDS stand for?
Sudden acquired retinal degeneration syndrome
How do dogs with SARDS present?
Acute onset of blindness that lasts days to weeks +/- PU/PD, polyphagia, weight gain
What are the ‘3 F’s’ that are characteristic of a patient with SARDS?
Fat, five, female
What bloodwork changes will you find in a patient with SARDS?
Hyperadrenocorticism
What ocular findings are consistent with a SARDS patient?
Normal fundus initially that degenerates over time
How is SARDS diagnosed?
Electroretinogram - no electrical function/flatline
T/F: Optic neuritis is a clinical symptom rather than a single disease.
True
Optic neuritis is usually unilateral or bilateral?
bilateral
How do patients with optic neuritis present?
Pupils are fixed and dilated
What is seen on a fundic exam in patients with optic neuritis?
ONH is hyperemic and elevated with hemorrhages on the surface
The ONH may appear normal if retrobulbar nerve is affected
What are the causes of optic neuritis?
Infectious diseases
Inflammatory/immune-mediated - GME
Neoplastic
Trauma
Idiopathic
How is optic neuritis diagnosed?
Typical clinical signs, normal ERG, and MRI
How is optic neuritis treated?
Treat underlying cause and systemic anti-inflammatory drugs
What is the prognosis for vision in optic neuritis patients?
Variable - guarded to poor
What are the ddx for optic nerve atrophy?
Glaucoma, PRA, orbital disease, optic neuritis, trauma (esp. horses)
What happens to the optic disk in patients with optic nerve atrophy?
The disc loses myelin and appears pale - may look like a cats eye
What clinical sign is associated with optic nerve atrophy?
blindness
