Ophth - posterior segment conditions

Question 1

What are some normal fundus variations?

Answer 1

Presence or absence of tapetum
Colour of tapetum
Amount of pigment of retinal pigment epithelium of non tapetal fundus

Question 2

When does the tapetum tend to be blue?

Answer 2

When it is not fully developed - in puppies and kittens

Question 3

Where is retinal pigmented epithelium found?

Answer 3

In the non tapetal fundus

Question 4

Where is the optic disc found?

Answer 4

Can be in the tapetal or non tapetal fundus - varies between individuals

Question 5

What is the difference between cats and dogs optic discs?

Answer 5

Cats - non myelinated, usually looks grey
Dogs - more white, can see blood vessels on it

Question 6

What can cause blindness?

Answer 6

A lesion anywhere along the visual pathway can cause blindness
eg. Ocular media opacity - eye itself
Retinal dysfunction
Optic nerve dysfunction
Optic tract lesion
Chiasm lesion
Visual cortex lesion - in brain

Question 7

Hoe can you test an animals retina?

Answer 7

Electroretinography
Pupillary light reflex
Dazzle reflex
Menace response

Question 8

How does electroretinography work?

Answer 8

Electrode in gold contact lens is placed on eye, and needles are placed on head to ground and act as reference electrode
Shine measured intensity flash into eye
Electrode in contact lens collects retinal response
Measures electrical activity/action potential of stimulus

Question 9

How does the pupillary light reflex work?

Answer 9

Light shone in one eye will cause both irises to constrict
Photoreceptors send impulse to chiasm - some run down other side down oculomotor nerve

Question 10

What is the dazzle reflex?

Answer 10

Similar to pupillary light reflex but facial nerve causes eye to blink/squint

Question 11

What is the menace response?

Answer 11

Advancing hand causes blink

Question 12

When is the menace response developed in puppies and kittens?

Answer 12

Not until 8-14 weeks

Question 13

What does cateracts look like on ocular ultrasound?

Answer 13

Opacity in the lens - hyperechoic (white) lens

Question 14

What does detached retina look like on ocular ultrasound?

Answer 14

Like a seagull

Question 15

What is a persistent hyaloid system?

Answer 15

Where the neonatal system hasnt regressed which can cause lens abnormalities, cateract or bleeding in the vitreous humour

Question 16

What are two causes of vitreal opacity/haze?

Answer 16

Asteroid hyalosis
Synchisis scintillans

Question 17

What is asteroid hyalosis? What does it look like?

Answer 17

When calcium phospholipids are suspended in the gel at back of the eye
Look like a starry sky - dont move

Question 18

What is synchisis scintillans? What does it look like?

Answer 18

When mobile cholesterol particles in liquefied vitreous
Looks like a snow globe

Question 19

What is vitreal syneresis? What can it lead to?

Answer 19

When the vitreous liquefies - can lead to retinal detachment

Question 20

What is retinal dysplasia?

Answer 20

Abnormal retinal development during embryonic growth - dark lines/folds in the retinal sheet where layers have been incorrectly laid down

Question 21

What are the two types of retinal dysplasia?

Answer 21

Multifocal
Total

Question 22

What does retinal inflammation look like?

Answer 22

Hyporeflective tapetal lesions - dark patches
White/cream lesions in non-tapetum

Question 23

What is active chorioretinitis?

Answer 23

Inflammation of the retina and choroid (closely associated structures)

Question 24

What does active chorioretinitis look like?

Answer 24

Infiltrates of protein/cells across damaged blood retinal barrier
Multifocal bullous retinal detachments - look like blisters

Question 25

What causes the bullous retinal detachments in active chorioretinitis?

Answer 25

Inflammatory fluid accumulating under the retina and pushing it off the choroid

Question 26

What does inactive chorioretinitis look like?

Answer 26

Hyperreflective tapetal lesions Pigmentation of the tapetum Depigmentation in a non tapetal lesion

Question 27

Why do you get hyperreflexctive tapetal lesions in inactive chorioretinitis?

Answer 27

The retina gets thinner Can partially reattach - tapetum appears shinier in these areas as there is less tissue between you and the tapetum

Question 28

What most commonly causes retinal haemorrhage?

Answer 28

Systemic hypertension - hypertensive retinopathy

Question 29

What does hypertensive retinopathy cause?

Answer 29

Vascular tortuosity - wiggly Vessel bleeding Haemorrhages Multifocal bullous detachments

Question 30

What are the different types of retinal detachment?

Answer 30

Serous Epulsive haemorrhage Subretinal cellular infiltrate Granuloma Solid tissue/tumour Tears/holes

Question 31

What disease can cause retinal degeneration?

Answer 31

Inherited progressive retinal atrophy

Question 32

What changes to the retina does inherited progressive retinal atrophy cause?

Answer 32

Hyperreflectivity - thin retina Vascular attenuation - blood vessel atrophy as cells dying so dont need blood Night blindness

Question 33

What happens in inherited progressive retinal atrophy?

Answer 33

Rods and cones die - rods first

Question 34

What is sudden acquired retinal degeneration (SARDs)?

Answer 34

Acute degeneration of the retina for unknown cause There is no electrical activity in neurosensory retina

Question 35

What does total retinal atrophy look like?

Answer 35

No blood vessels remaining Very hyperreflective tapetum

Question 36

What drug can cause total retinal atrophy?

Answer 36

Enrofloxacin

Question 37

What is optic coloboma?

Answer 37

Missing tissue - the optic nerve did not develop Blood vessels dont go all the way onto the optic nerve because its not there - disappear down it like a waterfall

Question 38

What species are prone to optic nerve disease?

Answer 38

Collies - collie eye anomaly

Question 39

What is collie eye anomaly?

Answer 39

Chorioretinal dysplasia Bizarre branching vessels Can cause haemorrhage and vision loss

Question 40

What is optic neuritis? What does it look like?

Answer 40

Inflammation of the optic nerve head - looks fuzzy

Question 41

What is papilloedema?

Answer 41

When the optic nerve head is pushed forward secondary to increased intracranial pressure No exudate, cells, blood, blood vessels look straight as if they are climbing a hill

Question 42

What is glaucoma?

Answer 42

Increase intraocular pressure - due to reduced draining of aqueous humour through the iridocorneal drainage angle

Question 43

What is the normal intraocular pressure in the eye?

Answer 43

10-25mmHg

Question 44

What intraocular pressure suggests glaucoma?

Answer 44

More than 30mmHg

Question 45

What intraocular pressure suggests uveitis?

Answer 45

Less than 10mmHg

Question 46

What are two inherited causes of primary canine glaucoma?

Answer 46

Goniodysgenesis - pectinate ligament dysplasia Primary open angle glaucoma (POAG)

Question 47

What are the clinical signs of glaucoma (non-chronic)?

Answer 47

Pain Blindness Conjunctival congestion Episcleral hyperaemia - red eye Corneal oedema - blue tint to eye Mydriasis - dilated pupil

Question 48

What are the clinical signs of chronic glaucoma?

Answer 48

Globe enlargement Secondary lens luxation Cataracts Phthisis bulbi - shrunken globe due to degenerate ciliary body not producing aqueous

Question 49

How do you diagnose glaucoma?

Answer 49

Tonometry - measure intraocular pressure More than 30mmHg - suggests glaucoma

Question 50

What are the different types of tonometers?

Answer 50

Indentation tonometry - cheap but tricky to use Applanation tonometry - expensive, accurate but need local Rebound tonometry - expensive, accurate, no local needed

Question 51

What can you use to treat glaucoma medically?

Answer 51

Carbonic anhydrase inhibitors Beta blockers Prostaglandin analogues

Question 52

How do carbonic anhydrase inhibitors treat glaucoma?

Answer 52

Inhibit the ciliary body from creating bicarbonate ions so cant draw water into aqueous So reduce aqueous production

Question 53

How do beta blockers treat glaucoma?

Answer 53

Reduce aqueous production

Question 54

How do prostaglandin analogues treat glaucoma?

Answer 54

Increase aqueous outflow - open an outflow route for the aqueous through the uveoscleral outflow & out into more superficial blood vessels

Question 55

When should you not use prostaglandin analogues to treat glaucoma?

Answer 55

In uveitis - pgs are pro-inflammatory In cats - dont work

Question 56

What surgical treatment is there for glaucoma patients that can still see?

Answer 56

Gonioimplant - increase outflow Transcleral cyclophotocoagulation - decrease output of aqueous

Question 57

What surgical treatment is there for glaucoma patients that are blind?

Answer 57

Enucleation Evisceration and intrascleral prosthesis - prosthetic eye