Retina Flashcards
What can you see on a fundic examination?
- Direct visualization of retinal blood vessels (often in pairs)
- Optic nerve (CNS)
- Vitreous (transparent gel-like body between the lens and retina)
Vitreal floaters appearance
- Can’t see the fundus
Clinical relevance of vitreal degeneration or asteroid hyalosis
- Interfere with vision and viewing the fundus
- Otherwise it’s a pretty normal age related change
Another name for vitreal degeneration
- Ateroid hyalosis
Characteristics of dog fundic vessels
- Holangiotic fundus
- Retinal vessels arcuate over the optic nerve
- Optic nerve is myelinated and varies in shape
- Color related to coat color
- May or may not have tapetum
Is tapetum usually in the superior or inferior fundus?
- Superior
Characteristics of cat fundus?
- Holangiotic fundus
- Large yellow-green tapetal area
- Optic nerve in the tapetal area
- Vessels arise from edge of optic nerve
- Non-myelinated optic nerve (appears small, round, and dark)
Equine fundus appearance
- Paurangiotic
- Retinal capillaries extend a few millimeters from the edge of optic nerve
- Optic nerve is elliptical and in pigmented area
- Variable colors of tapetum and pigmented areas by coat color
Rabbit fundus appearance
- horizontal optic nerve
- merangiotic (vesels in a certain region)
Bird eyes
- Pectin
- PIgmented vascular supply overlying the optic nerve
Bovine fundus
- Vessels in front of the retina
Do camelids or pigs have a tapetum?
- No
What is the tapetum?
- Reflective layer in choroid
Where is tapetum relative to the retina?
- Deep
Function of tapetum
- Reflects light back to the photoreceptor cells
Pigment in retinal pigmented epithelium over tapetal area
- Does not exist
- Allowing light through
Tapetal area and size of dog
- Smaller dogs have a smaller tapetal area
- Length of coat related to line of demarcation
Where does retinal detachment occur?
- Between the photoreceptors and retinal pigmented epithelium
How many layers of the retina?
- 10 layers
- see diagram in the notes
Which layer of the retina is impacted by glaucoma?
- Nerve fiber layerayer of the retina?
Where is the nerve fiber layer of the retina in relation to the rest of it?
- Innermost layer
What comprises the nerve fiber layer of the retina?
- Ganglion cell axons
- These axons then extend to the optic disc and form the optic nerve
Blood supply to nerve fiber layer of the retina
- Has retinal vessels
How does glaucoma impact the nerve fiber layer of the retina?
- It causes pressure damage
Photoreceptor layer
- Contains the rods and cones
Rods - what for?
- Night vision
Cones - what for?
- Day vision, color, and acuity
Which cell type (rods or cones) is predominant in 1.) domestic animals and 2.) birds/reptiles?
- ) Domestic animals: rods
2. ) Birds/reptiles: cones
Which diseases will impact the photoreceptor layer
- Anything causing retinal detachment
- PRA
- SARDS
Causes of retinal disorders
- Hereditary or acquired as result of toxin, virus, nutrition, trauma, septicemia, others
- Congenital disorders present at birth
- Degenerative disorders
Which antiparasitic is most commonly implicated for retinal disorders in herding breeds?
- Ivermectin
What are some of the more common causes of retinal disease in dogs?
- Infectious diseases
- Not as much trauma
Collie eye anomaly 4 parts
- Choroidal hypoplasia
- Optic nerve coloboma
- Retinal detachment
- Hemorrhage
Coloboma
- Hole
- E.g. optic nerve coloboma is a hole in the optic nerve
Inheritance of collie eye anomaly
- Hereditary
Clinical significance of collie eye anomaly
- Might not affect vision, but could
- Hereditary
- VIRTUALLY ALL COLLIES HAVE THIS
When does retinal dysplasia or dystrophy occur?
- At birth
- Occurs during retinal development
Who gets retinal dysplasia or dystrophy?
- Springer spaniel
- Likely not clinically significant but does affect if you should breed or not
Appearance of retinal dysplasia or dystrophy
- Geographic retinal dysplasia (weird line on the retina)
- Retinal folds (little spots
Two categories of diseases causing retinal degeneration
- Hereditary
- Acquired
What clinical sign can help you distinguish hereditary vs acquired causes of retinal degeneration?
- Bilateral = hereditary
- Asymmetrical/unilateral = acquired (more often)
IN GENERAL
Major cause of hereditary retinal degeneration
- PRA or progressive retinal atrophy
Who gets hereditary retinal degeneration?
- Many breeds and types
- Age of onset varies by breed
Acquired causes of retinal degeneration
- Toxins
- Trauma
- Nutritional
- Glaucoma
- SARDS (immune mediated)
What does SARDS stand for?
- Sudden acquired retinal degeneration syndrome
Who gets SARDS?
- Dachshunds and Brittany Spaniels
Progressive retinal atrophy - does the retina develop normally?
- Yes, and begins to degenerate after developing normally
Clinical signs of PRA
- Lose rods first (night vision)
- Dilated pupils as it progresses
- Bright and shiny fundus
- Blindness as retina thins
- Cataracts develop later in the disease
Course of disease for PRA?
- Progressive
- Once retina degenerates they develop cataracts –> LIU –> glaucoma or luxation –> enucleation
Treatment for PRA
- Not super treatable
- Can supplement with Ocuglow (fatty acids, omega 3s , and high levels of vitamin A)
Appearance of fundus in a dog with PRA
- Vascular attenuation
- Hyper-reflection
- Usually very dilated pupils
What is OFA?
- Eye registration certification
- Companion Animal Eye Regsitry
What is optigen?
- Genetic testing for inherited eye diseases in dogs
Appearance of retinal scarring?
- Can be incidental
- Looks like little spots on the retina
- Often well delineated
- Should make a note
- In a horse this is more concerning
Can you localize blindness by PLRs?
- No
SARDS clinical signs
- Sudden onset blindness or progressive over a few weeks
- Pupils are dilated and slow to respond or non-responsive
Signalment of SARDS
- Middle-aged (female more common)
- Dachshund, Schnauzer, Birtany Spaniel
- History of weight gain, PU/PD/PP 50% of cases
- Blood work may suggest adrenal disease
Diagnosis of SARDS
- High degree of suspicion based on exam (acutely blind with normal appearing eyes)
- ERG
- Fundic exam
Fundic exam with SARDS: Early vs Late onset
- Early onset it appears normal
- Late you’ll see hyperreflectivity
ERG with SARDS
- Flat line
How can you differentiate optic neuritis from SARDS based on ERG?
- ERG is normal with optic neuritis
Treatment for SARDS
- No effective treatment currently
- May give steroids and doxycycline in some cases
Major dfdx for a dog with dilated pupils, slow to respond, and sudden onset blindness
- Neoplasia
- Optic neuritis
- SARDS
Optic neuritis clinical signs
- Acute blindness
- Dilated pupils
- Slow to no response
Appearance of optic nerve with optic neuritis
- May appear hyperemic, fuzzy, raised, or it may appear normal if lesion is extraocular
How can you distinguish optic neuritis from SARDS?
- ERG
Do you need an ERG if the fundus looks abnormal?
- No
- Something is wrong at the level of the fundus
- Only need an ERG to differentiate SARDS from optic neuritis
What causes retinal detachment?
- Fluid or exudate from choroidal vessels accummulates between photoreceptors and RPE and elevates the retina, causing acute blindness
Where is the retina attached?
- To the optic nerve
- Also right behind the iris
Causes of retinal detachment?
- Hypertension
- Trauma
- Lens luxation
- Systemic disease (chorioretinitis, neoplasia, infectious disease, immune-mediated disease, idiopathic)
Appearance of retinal detachment on exam?
- Ribbon of undulation
- Retina looks like a tongue coming at you
- Retina is floating up
Treatment and prognosis of retinal detachment
- If you treat the primary cause immediately, you may restore vision within a few weeks
Detached retina example with light source only
- look at the piecture because i found it confusing
Diagnostics for retinal detachment
- Normal PE & blood work
- Negative titers (tick, fungal, toxo, lepto)
- Brucella, Bartonella
- Chest films
- Respond to prednisone
- Can take out the eye and do histopath if it’s gone already
FIP granuloma appearance
- Look at the nice pictures
Retinal detachment appearance on ultrasound
- You can see it
Giant retinal tear and disinsertion - who gets?
- Common presentation for young Shi Tzu dogs with acute blindness
Treatment for a giant retinal tear
- Surgical reattachment to restore vision
- Hole develops so the retina detaches superiorly
- You can no longer see the optic nerve because retina has come loose
- Make sure you can differentiate from billowing detachment
Most common causes of feline hypertensive retinopathy?
- NOT SARDS!!!!
- Infectious diseases and tumors
At what BP do cats get retinal detachment?
230 mmHg
- MEASURE BP IN ACUTELY BLIND CATS
Causes of feline hypertensive retinopathy
- Hyperthyroid
- Renal failure
- Primary?
Treatment of hypertensive retinal detachment
- Amlodipine
- Treat underlying disease based on lab work
- CBC/Chem/UA
- T4
- Chest rads and ultrasound
When do you want to recheck BP after starting a hypertensive cat on amlodipine?
- The next day
