Retina and Optic Nerve

Question 1

What causes Retinal Dysplasia?

Answer 1

• Usually inherited
  
  • can be associated with multiple ocular anomalies
• Other causes:
  
  • maternal viral infections
    
    • canine herpes and parvo viruses
    • feline panleukopenia
  • Vit A deficiency
  • X-ray irradiation
  • Drug toxicities
  • Intrauterine trauma

Question 2

What are the features of Retinal dysplasia?

Answer 2

• Retinal folds
  
  • dots, linear, or V/Y shaped
  • dull grey streaks in tapetum
  • depigmented or white in non-tapetal
• Geographic retinal dysplasia
  
  • larger, irregular often horseshoe-shaped hyperreflective lesion in tapetal fundus
• Retinal detachment - most severe form

Question 3

What is Hereditary Oculoskeletal dysplasia

Answer 3

• Retinal dysplasia in Labrador Retrievers
• Incomplete dominant ocular abnormalities
  
  • cataracts, vitreous strands, persistent hyaloid remnants, retinal folds, retinal dysplasia, rhegmatogenous retinal detachments
• Recessive-skeletal abnormalities
  
  • Short forelimbs and abnormal radius and ulna, hip dysplasia, hypoplasia of anconeal and coronoid processes
• Similar condition in Samoyeds

Question 4

What is Collie Eye Anomaly (CEA)?

Answer 4

• Collies
  
  • High prevalence
    
    • reduction due to selective breeding
  • Other breeds: shetland sheepdogs, australian shepherds, Border collies
• Simple autosomal recessive suspected - but condition may be polygenic
• Abnormal mesodermal differentiation
  
  • Choroidal hypoplasia
    
    • Hallmark sign
    • Incidentally found (no clinical signs)
• Optic nerve coloboma
  
  • More severe signs
  • Retinal detachment
  • hyphema

Question 5

What are the clinical signs of progressive retinal atrophy?

Answer 5

• Bilateral - progressive loss of vision - blindness
• Decreased night vision (nyctalopia) usually first sign
• Progressive decrease in PLR
• Larger than normal resting pupil size
  
  • Owner will sometimes report increase in “eye shine”
• Cataract formation in very late stages

Question 6

What is Sudden Acquired Retinal Degeneration Syndrome (SARDS)

Answer 6

• Acute photoreceptor death
• Usually middle aged to older dogs
  
  • females overreptresented
• All breed affected
• Associated clinical signs
  
  • may have ‘Cushing’s-like’ signs for weeks or months prior to vision loss

Question 7

What are the clinical signs of SARDS?

Answer 7

• Acute vision loss
• Variable PLR
  
  • Chromatic PLR
  • Red light negative
  • Blue light positive
• Fundic exam
  
  • Normal initially
  • Chronic cases
    
    • retinal degeneration

Question 8

How is SARDS diagnosed?

Answer 8

• Electroretinogram (ERG)
• May have elevated ALP, or other Cushing’s like changes on blood work
  
  • less commonly diagnosed with Cushing’s via traditional screeding tests

Question 9

What is the treatment for SARDS

Answer 9

• No proven treatment
• Permanent blindness

Question 10

What are the effects of Retinal detachments on vision?

Answer 10

• Small detachments - no deficit
• large detachments - visual deficit/blindness

Question 11

What is Rhegmatogenous retinal detachment

Answer 11

• Retinal tear present which allows liquified vitreous to enter sub-retinal space
• Primary ocular disorder (previous cataract surgery, inherited vitreal degeneration, etc)

Question 12

What is Non-rhegmatogenous retinal detachment

Answer 12

• Remains attached at ora ciliaris retinae & optic disc
• Serous sub-retinal fluid-bullous retinal detachment
• Exudative retinal detachments-inflammatory or exudative sub-retinal fluid
• Systemic disease

Question 13

What are the differentials for Non-rhegmatogenous Retinal detachment?

Answer 13

• Depends on type of sub-retinal fluid/material
• Exudate (cloudy or discolored, yellow)
  
  • same as chorioretinitis (i.e. posterior uveitis) ⇢ suspect systemic infection
• Transudate (clear)
  
  • Aka Bullous
  • Hypertension
  • Hypoproteinemia
  • Idiopathic (steroid responsive)
    
    • dog specific
• Always perform systemic work-up
  
  • CBC/chemistry panel/UA
  • Blood pressure
  • CHest radiographs
  • Titers/antigen tests

Question 14

How is Retinal detachments repaired?

Answer 14

• Only appropriate for rhegmatogenous detachments
• Laser retinopexy
  
  • 2 rows of burns around detachment to create adhesions
  • Prophylactic vs. barrier
• Retinal reattachment

Question 15

What are the possible etiologies for Retinal hemorrhages?

Answer 15

• Anemia
• COagulopathy
• Systemic hypertension
• Hyperviscosity
• Systemic infections that cause vasculitis

Question 16

What is the diagnostic approach to retinal hemorrhages

Answer 16

• Thorough PE
• CBC, Chemistry, UA
• Blood pressure
• Clotting times
• BMBT
• Chest radiographs
• Titers/antigen testing if any suspicion of infectious cause

Question 17

What is Optic neuritis?

Answer 17

• Optic nerve inflammation
• Unilateral or bilateral
• Can involve any segment of optic nerve (intraocular vs retrobulbar)
• Associated with sudden blindness, fixed and dilated pupils
• Intraocular involvement:
  
  • disc appears swollen, elevated, and hyperemic, with indistinct margins = papillitis
• Retrobulbar involvement:
  
  • optic disc will appear normal
  • need ERG to distinguish from SARDS

Question 18

What are the differentials for Optic Neuritis?

Answer 18

• Infectious
  
  • Fungal
  • Tick-borne encephalitis or ehrlichiosis
  • Protozoal - toxoplasmosis
• Neoplasia
  
  • lymphoma
  • orbital/retrobulbar neoplasia
• GME
• Immune mediated
• Idiopathic
• Other:
  
  • Orbital abscess/cellulitis
  • Trauma
  • Toxins
  • Vitamin A deficiency

Question 19

What is the diagnostic approach to Optic Neuritis?

Answer 19

• CBC, chemistry panel, USA
• titers/antigen tests for infectious organisms
• Chest radiographs
• MRI or CT scan
• CSG Tap
• Thick of Optic neuritis as a neurologic disease

Question 20

What is the treatment for optic neuritis

Answer 20

• Treat primary cause
• Systemic steroids (immunosuppressive dose)
• Oral antibiotics (empiric)
• Prognosis for vision = poor

Question 21

What are the hallmark fundoscopic signs of Progressive Retinal Atrophy?

Answer 21

• Tapetal hyper-reflectivity
• Retinal attenuation of blood vessels
• Optic disk pallor