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Ophthalmology (all species) > Ophthalmology conditions of the lens and retina > Flashcards

Ophthalmology conditions of the lens and retina Flashcards

1
Q

Lens embryology and anatomy

A

Forms from ectoderm invagination
Anterior epithelium forms anterior lens capsule
Posterior epithelium forms the lens

SO the lens capsule at front is much thicker than at back

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2
Q

How is the lens kept transparent

A

Because the lens crystalline proteins have cysteine amino acids with SH groups that attract the right amount of water to keep the lens transparent
- If these aggregate get cataracts

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3
Q

Which part of the lens forms before birth and what grows through life

A

Lens nucleus forms before birth
Cortical fibres grow through life; lens ageing

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4
Q

How does nuclear sclerosis occur

A

Due to compaction of the lens nucleus with age causing an increased refractive indec and greying of the tissue

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5
Q

How to look at cataracts with direct distant ophthalmoscope

A

Use 10 dioptres (this is the anterior segment)

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6
Q

Difference between how a cataract and nuclear sclerosis look on ophthalmoscope

A

Cataract is solid white; can see spiders web of black across lens

Nuclear sclerosis is a haze; can still see the vessels at the back of the eye

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7
Q

What type of congenital cataracts do we see in cocker spaniels and west highland whites

A

Anterior capsule opacities because anterior epithelium is abnormally proliferating

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8
Q

What type of non-congential inherited cataract do we see in retrievers

A

posterior subcapsular cataract that is usually non progressive

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9
Q

How are diabetic cataracts formed

A

With high glucose in lens, get saturation of hexokinase
–> So gets acted upon by aldose reductase to form sorbitol

Sorbitol has much higher osmotic potential than glucose so sucks water into the lens which rutures the fibres and causes lens to expand

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10
Q

How does progressive post-PRA metabolic cataracts work

A

Esp in cockers and miniature poodles
Get cataract due to damage of lens by toxic metabolites of lipid peroxidation formed during retinal degeneration

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11
Q

How is sunlight involved in senile cataract formation

A

Causes photo-oxidation of cysteine AAs in lens proteins, causing disulphide bridgge formation and aggregation of crystallin proteins
= catacts

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12
Q

What is the gold standard cataract surgery

A

Phacoemulsification
- Make incision into lens, fire ultrasonic water in to break up the cataract
Success rate 80%; but expensive

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13
Q

Why are diabetic cataracts prone to causing lens-induced uveitis

A

Because excess water causing lens swelling creates micro-fractures in lens capsule (which can’t expand) and allows lens proteins out; causing inflammatory reaction

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14
Q

Criteria for successful cataract surgery

A

No other ocular disease
No other systemic disaese

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15
Q

What does it suggest if an animal stops wanting to go out at night

A

May have progressive retinal atrophy; rods are damaged first and these are responsible for night vision

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16
Q

Why do we avoid cataract surgery in cases with retinal detachment

A

Reomval of lens causes more damage and detachment and can make animal go blind

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17
Q

What are some signs of lens luxation

A
  • Acute glaucoma due to blockage of aqueous drainage
  • Aphakic crescent; if lens has gone anterior
  • Corneal oedema where the lens has abbutted the cornea
  • Iridodonesis (wobble of iris now lacking lens support)
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18
Q

What is primary lens luxation

A

Where lens luxates due to inherited weakness in the zonules
- Get total detachment of the lens
Terriers have congenital zonule weakness

19
Q

What is secondary lens luxation

A

Where globe expands due to glaucoma and zonules are torn due to enlargement so lens comes out of place
–> The lens stays behind the iris so is subluxated

20
Q

What is Haabs streir

A

White line in eye due to fracture of descemets membrane as eye has expanded due to glaucoma (can be seen therefore in secondary lens luxation cases)

21
Q

How to tell the difference between corneal and lens opacity

A

If the detail of the iris is clear then probably a lens problem
If there is whiteness on front of eye and iris not clear; will be corneal

22
Q

What does a too thick or too thin retinal vein suggest

A

Too thick; hypertension
Too thin; retinal degeneration, anaemia etc

23
Q

Where does detachment in retinal detachment occur

A

In the virtual space between the photoreceptors and the retinal pigment epithelium

24
Q

What is retinal dysplasia

A

An inherted abnormality in retinal development
Can range from streaks, spots to complete detachment

In labradors it is associated with skeletal dysplasia

25
Q

What is involved in collie eye anomaly

A

Optic nerve head coloboma
Chorioretinal dysplasia; just see a huge vessel in choroid and white sclera instead of lots of small vessels

+ retinal issues; retinal detachment, haemorrhage

26
Q

How does generalised progressive retinal atrophy work

A

= inherited degeneration
Rods have genetic defect so die; then cones die due to oxidative stress as rods not there to use up O2

Present with night blindness progressing to total blindness

27
Q

Presentation of generalsied progressive retinal atrophy

A

Hyperreflective tapetum because rods not there to absorb light
Very white optic nerve

Thin retinal blood vessels; BECAUSE high O2 so don’t get stimulation of VEGF cytokines to keep them there normally

28
Q

Which breed has generalised progressive retinal atrophy NOT been bred out of

A

PRogressive rod cone degeneration in poodles, labs, cocker spaniels
–> Because don’t present until 5-6 years old and have bred by this time

29
Q

How can we test for PRA using electroretinography

A

Use high intensity blue light; rods see this less than a high intensity red light

30
Q

What causes retinal pigment epithelial dystrophy

A

Disease of retinal pigment epithelium; causes it to stop phagocytosing and removing photoreceptor debris at end of day
–> Get blobs of photoreceptor debris on retina

+ linked with vitamin E deficiency

31
Q

What infectious causes can lead to chorioretinal inflammation and localised degeneration

A

herpes virus
Distemper virus
Visceral larva migrans

32
Q

Why do we still see a pupillary light reflex in sudden acquired retinal degeneration i.e rods and cones are dead

A

Because there are opsins in ganglion cells which can do the PLR

33
Q

What is sudden acquired retinal degeneration

A

Where an antibody mediated response against a molecule in the phototransduction pathway (recovorin) causes photoreceptor to stay ‘on’ and undergo apoptosis

So see acute blindness
Retina LOOKS normal but there is a flat electroretinogram

34
Q

What things are associated with sudden acquired retinal degeneration

A

Increased blood liver enzymes, cushings disease
Small breeds of middle age

35
Q

What does box carring of retinal vessels suggest

A

Hypertension
Use amlodipine to reduce systemic blood pressure and prevent retinal detachment

36
Q

How can anaemia lead to retinal haemorrhage

A

Vascular endothelium is ischaemic so dysfunctions and can cause haemorrhge

37
Q

What do grey spots in the retina often with overlying retinal detachment suggest

A

Posterir uveitis

38
Q

How does taurine deficiency retinopathy present

A

Central retinal degeneration and tapetal hyperreflectivity
0 Normalising siet will stop further progression

39
Q

How can vitamin E deficiency lead to progressive blindness and ataxia

A

Get deposition of lipofuscin in brain and retina
–> Causes retinal pigment epithelial dystrophy signs

40
Q

Where do inhertied non-congenital cataracts start from in boston terrior/staffie/mini schnauzer

A

Suture lines
= progressive

41
Q

Where do inherited cataracts in retrivers start frmo

A

POsterior subcapsule
= non-progressive usually

42
Q

Where do inherited non-congenital cataracts start in adghan, poodle, welshs pringer, GSD

A

Equator
Progresses to blindness except in GSD doesn’t

43
Q

What what cause a hyperreflective retina with lear boundaries of the lesion

A

Infectious causes of chorioretinal inflammation
e.g distemper, herpes virus, visceral larval mirans

Ophthalmology (all species) (8 decks)

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