The Fundus - disorders & clinical anatomy Flashcards
When looking at the fundus, what is the order of structures visualized (anterior to posterior)?
- Retina
- Retina Pigmented Epithelium (non-pigemented zone = tapetal)
- Tapetal lucidum
- Choroid
- Sclera
RPE: what is meant by it being a “potential space”?
Becomes a “real space” in retinal detachment.
RPE sucks fluid out from this space ad creates a vacuum environment
Retinal detachment: RPE tries to “suck” the fluid from the leaky vessels of the detached retina -> RPE becomes Hypertrophied
Hypertension in cats causes retinal detachment
What determines color & size of the tapetum in dogs?
Age, size of dog, breed
Hyper-reflective tapetum
Structures are thinner in front of the tapetum
- Thin neurosensory retina;
Hypo-reflective tapetum
Structures are thicker in front of tapetum
- chorioreinitis (fluid accumuluates)
Identify
Optic Disc (normal)
Developmental Disorders
Retinal Dysplasia
- inciting cause
- affect on vision
Congenital problem in the retina;
- minimally affects vision unless total dysplasia occurs, which can cause retinal detachement
- multi-focal, geographic, total dysplasia
Developmental Disorders
Collie Eye Anomaly
- inciting cause
- 3 common types
Congenital / genetic => vision loss
- thinning of choroid (choroidal hypoplasia)
- coloboma
- detached retina, which can occur as a complication of a coloboma
- ubiquitous among collies!
Micropapilla and Optic Nerve Hypoplasia
- inciting cause
- diferentiating factor
- Congenital anomalies
- Optic Nerve Hypoplasia: smaller than normal optic nerve -> Avisual!
- Micropapilla: optic disc is smaller than normal -> Visual!
Colobomas
- inciting cause
- lesion
- congenital
- incomplete closure of optic fissure => retina herniates out
- vision deficit that is appreciable by humans depends on how big lesion is
Optic Neuritis
- inciting cause in dogs vs cats
- intraocular vs retrobulbar types
- presentation
- inflammation of the optic nerve
- multiple etiologies: immune-mediated (dogs), infectious (cats), neoplasia
- typically bilateral ; can be intraocular or retrobulbar forms (The retrobulbar space lies inside the extraocular muscle cone, behind the globe)
- presents as acute blindness with absent PLRs
- Intraocular: swollen optic disc
- Retrobulbar: normal optic disc
“cuts off tranmission of optic nerve information”
What are the 3 most important Retinal Degenerative Disorders?
Progressive Retinal Atrophy (PRA)
- inciting cause
- pathogenesis
- clinical signs
- diagnostic tests
- Ophtho Exam findings
- treatment
Inciting Cause:: Genetic
Pathogenesis
- retina devleops normally, then deteriorates later in life. rods degenerated first (followed by cones) => condition progresses to complete blindness
Clinical signs: owners notice dim-light vision deficits
Diagnostics:
- visualizing fundus via ophthalmic exam + Hx
- diminshed menace and PLR; mydriasis even if in bright-lit room
- Maze test: set up objects in room -> dog freezes in their tracks / start bumping into stuff when you turn lights off
Ophtho findings: Hyperreflectivity (due to retinal thinning
Treatment: none, counsel owners on creating safe evironment at home for dog
Rods; dim/low-light vision, achromatic
Canine Sudden Acquired Retinal Degeneration Syndrome (SARDS)
- inciting cause
- pathogenesis
- clinical signs
- diagnostics
Inciting Cause:: Idiopathic canine disorder
Pathogenesis: unknown
Clinical signs: sudden onsent of blindness. Cushing-like signs (PU/PD, polyphagia, weight gain)
Diagnostics:
- fundus appears normal
- Definitive dx = electroretinogram -> allows ruleout of retrobulbar optic neuritis
Differential: retrobulbar optic neuritis: normal fundus = electroretinogram appears normal!
- electroretinogram: measures the electrical activity of the retina in response to light stimulus
Feline Central Retinal Degeneration (Taurine Deficiency Retinopathy)
- Cats suscpetible since they are obligate carnivores
- Rare nowadays because feline diets are supplemented with taurine
- Taurine deficient diets result in retinal degeneration & DCM
- Can halt disease in its tracts if you fix diet, but you cannot fix the already-present lesions
Treatment for Exudative Detachment
- Fix the hypertension
- Control the immune-mediated conditions (chorioretinitis)
- May remain if inciting cause is neoplasia/tumor
Treatment for Rhegmatogenous Detachment
Surgery!
- tear gets pinned back into place
Manifestations of Systemic Disease
What is the most common condition that causes hypertensive retinopathy?
Renal disease (cats!) => hypertension
Ophthalmoscope findings: retinal edema, retinal hemorrhage, retinal detachment
Manifestations of Systemic Disease
Chorioretinitis
- definition
- inciting causes
- ophthalmoscopic findings
- inflammation of choroid & retina
- several systemic etiologies: immune-mediated, infectious, neoplastic, idiopathic
- hyporeflective lesions (thickened / inflammed lesions!)
