16 - Retina & Optic nerve

Know how to recognize persistent hyperplastic primary vitreous, asteroid hyalosis and vitreal hemorrhage.

persistent hyperplastic primary vitreous

primary vitreous proliferates to form vessels and fibrous throughout vitreous, around lens, and into lens substance

can cause spontaneous hemorrhage

asteroid hyalosis

calcium or lipid deposits suspended in vitreous

move when eye moves → bounce back to original position when eye stops moving

clinically insignificant

secondary to inflammatory or intraocular neoplasia


Know the layers of the retina and the vascular patterns of common species.

  1. retinal pigmented epithelium

  2. photoreceptors (rods and cones)

  3. external limiting membrane

  4. outer nuclear layer

  5. outer plexiform layer

  6. inner nuclear layer

  7. inner plexiform layer

  8. ganglion cells

  9. nerve fiber layer

  10. internal limiting membrane

holangiotic

dogs, cats, cattle, sheep, pigs

blood vessels scattered throughout retina

paurangiotic

horses

vessels surround optic disc

merangiotic

rabbit

vessels run east and west

anangiotic

birds and reptiles

no blood vessels



What are the lesions seen in the condition known as collie eye anomaly? Which of these lesions interfere with vision? Is this a progressive disease? What do we recommend concerning breeding these animals?

  • choroidal hypoplasia

  • coloboma of optic disc → interfere

  • retinal detachment → interfere

  • intraocular hemorrhage → interfere with vision

  • excessive tortuosity of retinal vessels

  • vermiform streaks

CEA is not a progressive disease

recommend not to breed


Be able to describe/recognize the clinical presentation (history, clinical signs) associated with progressive retinal atrophy (PRA) and sudden acquired retinal degeneration (SARD). Be able to differentiate and diagnose PRA and SARD.

PRA

  • autosomal recessive

  • always bilateral

  • loss of vision → night vision first → rods

  • diminished PLRs

  • attenuation of vessels

  • tapetal hyperreflectivity

  • pale optic disk

  • depigmentation of the non-tapetum

  • cataract formation

  • may have some activity on ERG

SARD

  • sudden onset of day and night blindness

  • absent/sluggish PLRs

  • PU/PD PP → systemic illness

  • must have ERG to determine rods and cones are nonfunctional

differentiation

  • slow vs fast onset

  • presence of systemic illness

  • presence of other retinal changes

  • presence of activity on ERG or not


Describe the lesion(s) seen in feline central retinal degeneration (FCRD). What is one known cause of FCRD?

  • round to cigar shaped lesion in central retina

  • area within lesion is hyperreflective → retinal degeneration

  • associated with lack of taurine

  • may be associated with systemic disease


Know how to recognize a retinal detachment. What are the common causes of a retinal detachment? What are possible therapies for retinal detachment depending on the original cause?

  • hypertension

  • exudative/serous

  • neoplasia

  • congenital

  • trauma

  • idiopathic/immune-mediated/steroid responsive

  • inflammatory/infectious

medical: treat medical condition

surgical: retinopexy, scleral buckle, intravitreal reattachment


Know how to recognize retinal hemorrhage. What are the common causes of a retinal hemorrhage? What are possible therapies for retinal hemorrhage?

  • hypertension

  • thrombocytopenia

  • coagulopathy

  • DIC

  • hyperviscosity syndrome

  • radiation

  • senile

  • trauma

tx: treat systemic cause, corticosteroids, laser therapy

Be able to describe/recognize the clinical presentation (history/clinical signs) that may be associated with optic neuritis. What is an appropriate work-up for a patient with suspected optic neuritis? What are some possible causes of optic neuritis? What diagnostic test can you use to differentiate between optic neuritis and sudden acquired retinal degeneration (SARD)?

  • no PLRs

  • visual deficit

  • swollen optic disc

  • dilated retinal vessels


  • CSF analysis

  • ERG → use to R/O SARD

  • EEG

  • infectious disease testing


  • meningoencephalitis


tx: steroids, tx underlying disease


Know how to differentiate between optic neuritis and papilledema? What are some common causes of papilledema?

optic neuritis

  • no PLRs

  • visual deficit

papilledema

  • PLRs present

  • no visual deficit

  • edema of optic disc

  • elevation of disc surface above retina

  • caused by space-occupying mass → neoplasia, hemorrhage, hydrocephalus


Know how to differentiate active from inactive retinal/choroidal lesions (hyper-reflective vs. hyporeflective)

active

  • hyporeflective

  • borders are indistinct

  • perivascular sheathing/engorgement of vessels

  • retinal changes → hemorrhage, detachment, enlargement of lesion

inactive

  • hyperreflective

  • sharply defined borders

  • decreased vessel size

  • depigmentation