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Opthalmology > The Blind Eye > Flashcards

The Blind Eye Flashcards

1
Q

What order are layers of the retina passed through by light, and which direction does the neural stimulus travel?

A

> Light travels…
- Ganglion cells (ganglion cell axons form optic nerve, layers 8-10)
- Cells in inner retina (layer 5-7)
- Photoreceptors (rods and cones) in outer retina layer 2-4
- RPE outmost layer number 1
neural stimulus travels opposite direction then on to
- optic nerves
- optic chiasm (more decussation in dogs than in cats)
- optic tract
- optic radiation
- occipital lobe of cerebral cortex

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2
Q

What do the outermost and innermost layers of the retina lie next to?

A
  • outtermost next to choroid

- innermost next to vitreous

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3
Q

Which layer is the only non-neural layer?

A

Number 1 RPE 9retinal pigment epitherluim)

- nurturing layer

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4
Q

Which layer of the retina does glaucoma damage?

A

Ganglion cells

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5
Q

How may eyelid disease -> blindness?

A
  • severe drooping eg. in sniffer dogs w/heavy ears and foreheads
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6
Q

Tx drooping facial skin -> blindness?

A
  • Stades procedures of the upper eyelid
  • reduction palpebral aperture
  • facelift (“rhitydectomy”)
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7
Q

Why may severe drooping face not be noticed by owner?

A

Slips back into place when dog look dorsally

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8
Q

What corneal problems may -> blindness?

A 
> chronic corneal pathology -> 
- scarring
- vascularisation 
- pigment deposition
- KCS
- LPI/pannus/EK 
- sequestra (cats>horses>dogs)
- pigmentary keratitis (PUGS) 
> severe acute disease -> 
- scarring 
-ulcerative
- KCS related
- Traumatic in origin
- melting progression d/t severe inflam or infection
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9
Q

What is symblepharon and when is it commonly seen?

A

corneal problem
> adhesion of conjunctiva onto itself and cornea
- Kittens affected with cat flu esp if when v young (FHV, Bordatella, Calicivirus)
- FHV epithelial tropism -> corneal epithelial depletion and destruction of limbal stem cells -> conjunctiva advancement over cornea
- permenant focal/diffuse scar
- If infected

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10
Q

Tx symblepharon?

A

Stem cells transplant!!

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11
Q

What is pigmentary keratitis and when is it commonly seen?

A

corneal problem
> pigment and chronic corneal irritation
- specifically seen in pugs w/entropion (d/t limbus pigmentation)
- lower medial eyelid and medial canthus
- can -> blindness

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12
Q

What are PPMs? Ddx?

A

Uveal problem
> persistent pupillary membranes arising at iris collarette
- failire of regession foetal BVs
- congenital problem
- strands may span iris-iris, iris-cornea (LEUKOMA) slowly pregressive, iris-lens(CATARACT) usually progressive
- can worsen with age
> Ddx posterior/anterior synechia affecting PUPILLARY iris not iris colarettte

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13
Q

What does the uvea consist of?

A
  • iris: pupil motion, in contact with anterior lens and ICA [iridocorneal angle]
  • ciliary body: muscle and epithelium, produces AH and focuses lens
  • choroid + tapetum: eeds outer retina that lies on top of it
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14
Q

Which uveal problems may occour?

A

uveitis
> inflammation -> leakage plasma/blood
- turbid AH (flare) and ventral keratic precipitates
- hypopion (accumulation WBCs ventrally)
- hyphema
- clots in AC +- Vitreous
> muscle contraction
- pain (iris and ciliary body spasm)
- photophobia/miosis
> damaged endothelium -> corneal oedema
> iris adhesions (posterior synechia, anteria synechia and closure of the ICA)
> Development of PIFMs can also clog ICA
> Low IOP (helps distinguish from glaucoma)

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15
Q

What is a potential cause of sudden onset blindness in the cat?

A
  • renal disease -> ^ BP -> glaucoma, hyphema and retinal detachment
  • may occour in hours
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16
Q

What are PIFMs?

A
  • preiridial fibrovascular membrane - grows like ivy within eye
  • microscopic vascularisation
  • d/t chronic uveitis
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17
Q

Can posterior synechia affect vision?

A

yes cloud the pupil

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18
Q

Which species are most likely to develop 2* cataracts

A

Cats and horse , less common in dogs

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19
Q

Where do leaks occour w/ retinal detachment ?

A

between layers 1 + 2

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20
Q

How are cataracts and uveitis related?

A

> uveitis -> 2* cataracts
- slowly progressive, can beome mature over time
- in cats (sometimes horses and dogs) can -> lens luxation
cataracts -> phacolytic uveitis
- leakage of lens proteins (crystallines) -> aqueous humour
- loss of immune tolerance to naturally encapsulated protein

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21
Q

What is phagoclastic uveitis?

A
  • lens ruptures/breaks
  • commonly seen with diabetic cataracts d/t being made of sorbitol which keeps absorbing water
  • may be d/t trauma
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22
Q

What type of uveitis are cats and horses commonly affected by?

A

> recurrent uveitis (ERU/moon blindness/periodic ophthalmia)
- 1* insult eg. Leptospira horses, Toxo/viruses in cats
- breakdown of BOB (blood ocular barrier)
- anamnestic response triggered by epitopes of self antigen
- most recurrent uveitis considered IDIOPATHIC as @ time of investigation 1* cause is no longer present
cataracts and glaucoma
chronic nature

23
Q

Tx uveitis?

A
  • treat cuase if known
  • generally tx symptomatically (Anti-inflammatories)
    > Topical (affect ulcer healing and diabetes, but effective) start ^ freq application
  • prednisolone acetate [god penetration, harsh on ocular surface]
  • dexamethasone phosphate [less penetrating, kind to o surface]
  • NSAIDs [ do not affect diabetic control but ? efficacy] ketorolac, diclofenac etc.
    > Systemic (do not affect ulcer healing provided it is avascular) Antiinflammatory dose, immune mediated may require immunosuppressive dose
  • posterior uveitis and severe anterior uveitis where topical would be ineffective
  • steroid: Pred tablets
  • NSAID: Meloxicam, carprofen, flunixin meglumine
24
Q

Are use of topical steroids in a diabetic post-cataract surgery indicated?

A
  • theoretically no as affect pituitary-hypothalamic-adrenocortical axis
  • in practice not that relevant as high doses rarely necessary and taper off quickly
25
Q

Which vasculopathies can lead to blindness?

A
  • systemic hypertensionin cats
  • FIP/FeLV/FIV/Toxo (FFFT)
  • Fungal Infection
  • leishmania
  • Uveodermatological syndrome
26
Q

How does systemic hypertension in cats -> blindness?

A
  • systemic hypertension -> hyphema and haemorrhage into vitreous
  • retinal detachement
  • systemic problems too
27
Q

How does FFFT -> blindness?

A
  • protein in AC
    +- lesions in fundus
    +- systemic disease
28
Q

How may fungal infection -> blindness?

A
  • affects whole uvea esp fundus

- may affect resp tract too

29
Q

What opthamic effects may leishmania have?

A
  • panuveititis
  • keratitis
  • KCS
30
Q

What is uveodermatological syndrome?

A

= VKH-like syndrome

  • dogs
  • severe anterior AND posterior uveitis
  • severe skin lesions (depigmentation, less of hair and multiple skin lesions)
  • immune mediated disease against precursors of melanin
  • anywhere with pigment affected (eyes, skin, hair, meninges, middle ear..)
  • clinical signs include uveitis -> hyperpigmentation, scleral inflammation, dilated pupil d/t glaucoma
31
Q

What may uveitis result in?

A
  • uveitis -> hyperpigmentation
32
Q

What may cause anisocoria?

A
  • glaucoma -> dilation of difereing degrees in differnet eyes
33
Q

What is dyscoria?

A

Funny shaped pupil

34
Q

What is a cataract?

A
  • opacity in the LENS that blocks passage of light
  • small as a dot/large as whole lens
  • any shape
  • may be found in…
  • nucleus
  • cortex
  • equator
    > Do not confuse wth nuclear sclerosis
35
Q

What types of cataracts are possible?

A 
> congenital
- rarely progressive, usually idiopathic but do not cause uveitis
> PPMs
- persisnt pupillary membranes 
- progressive -> mature cataract, lens induced uveitis may occour 
- arise fom iris colarette 
> acquired
- see list of causes
36
Q

What may cause acquired cataracts?

A
  • inherited (K9, rarely cats)
  • DM (v common diabetic dogs, independent of glycemic control)
  • perforatin trauma (lens contact cat claw/thorn, blunt trauma without perforation rarely causes cataracts)
  • age related (slowly progressive)
  • hypocalcaemia (rare in dogs eg. hypoparathyroidism)
  • E. Cuniculi associated (rabbits and cats)
  • GPRA end stage cases
37
Q

What is GPRA?

A
  • generalised progressive retinal atrophy
  • inherited breed specific disease
  • slowly pregoressive
  • NOT painful
  • cannot stop progression
  • > blindness
38
Q

What are the defining features of diabetic cataracts?

A
  • progress rapidly
  • lens induced uveitis (conjunctival/episcleral hyperaemia and low IOP)
  • may -> 2* glaucoma d/t PIFMs if untreated
  • often show WATER CLEFTS of the anterior suture lines where lens material has dissolved
39
Q

What layer of the retina does glaucoma damage?

A
  • ganglion cells
40
Q

What vitreous problems are possible?

A

> congential

  • persist hyaloid vasculature (visable normally in calves acquired
  • syneresis (liquefaction, may -> retinal detachment in the shih-Tzu, seen spontaneously, with age and inflammation)
  • asteroid hyalosis (particulate matter, seen spontaneously, with age and/or inflammation; often seen with syneresis on ultrasound, if optically dense can interfere with sight)
41
Q

What congenital RETINAL problems are possible?

A

> dysplasia
- inherited in cavalier, springer and others
- malformed retina
- several forms (mild/folds, multifocal, generalised)
- latter may -> retinal detachment
- no tx, breeding advice
collie eye anomaly
- collies and sheltand sheepdgos
- choroidal hypoplasia lateral to optic disk
- may be assoc w/ coloboma of optic nerve head
- latter may -> retinal detachment, otherwise not assoc w/ blindness
- no tx, breeding advice

42
Q

What acquired retinal problems present acutely?

A

> SARD (sudden acquired retinal degeneration)
IMR (immune mediated retiniopathy)
- Both of these ^^ hard to differentiate and no tx available (try steroids for IMR if early, rare)
MUO/MUE/MUA (Meningitis of Unknown Origin)
Bullous retinal detachemnet
Toxic retinopathy
do ERG if no obvious lesions

43
Q

> SARD (sudden acquired retinal degeneration)

A
  • suden onset, bilateral
  • +- PUPD and cushingoid biochem
  • fundus looks normal
  • flat ERG d/t sudden photoreceptor death
44
Q

> IMR (immune mediated retiniopathy)

A
  • similar to SARD but no Cushingoid symptoms

- ERG may or may not be flat

45
Q

Tx and ddx of SARD and IMR

A

> Both of these ^^ hard to differentiate and no tx available (try steroids for IMR if early, rare)

46
Q

> MUO/MUE/MUA (Meningitis of Unknown Origin)

A
  • otherwise = granulomatous meningioencephalitis GME
  • grized/optic nerve forms
  • optic nerve head may/may not show hammorhage
  • ERG normal
  • may present with seizures/motor deficits
  • Tx: steroids
47
Q

> Bullous retinal detachemnet

A
  • systemic hypertension in cats

- rare form in dogs = steroid responsive RDt

48
Q

> Toxic retinopathy

A
  • cats with oral ENROFLOXACIN
  • ^ risk @ doses >5mg/kg but never zero risk
  • not associated with other fluoroquinolones
  • No tx but withdrawal drug to reverse some signs
49
Q

Which pathology presents as a chronic retinal disease?

A

GPRA (generalised progressive retinal atrophy

  • inherited
  • many dogs, some cats
  • pan-retinal degeneration at the end
  • no pain
  • gradual loss of vision (night blind -> day blind)
  • no tx
  • all other diseases end p looking like GPRA given time
50
Q

What clinical signs are seen with retinal atrophy GPRA?

A
  • hyper-reflective tapetum lucidum as retina thin so doesn’t block any light
  • marked attenuation of retinal vasculature
  • late stage -> cataracts
51
Q

What should always be considered if no obvious lesions are seen?

A
  • acute, might be IMR/SARDS - do ERG
  • consider GME
  • consider diseases of the optic nerve head
  • consider CENTRAL BLINDNESS
52
Q

What are the causes of uveitis in cats?

A

FFFT

  • FeLV, FIV, FIP, Toxoplasma
  • > recurrent cyclic uveitis (as in horses)
53
Q

Does diabetes cause cataracts in cats?

A

Rarely, but commonly does in dogs

Opthalmology (14 decks)

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