The Abnormal Size and Position of the Eye

Question 0

What does the prefix phac- pertain to?

Answer 0

The lens

Question 1

What does the prefix cyclo- pertain to?

Answer 1

Ciliary body

Question 2

What does the prefix kerat- pertain to?

Answer 2

The cornea

Question 3

What does the prefix blephar- pertain to?

Answer 3

Eyelid

Question 4

What does the prefix dacryo- pertain to?

Answer 4

Nasolacrimal system

Question 5

What does the prefix hyalo- pertain to?

Answer 5

The vitreous

Question 6

Which species have a closed orbit?

Answer 6

Humans and herbivores

Question 7

Which species have an open orbit?

Answer 7

Carnivores and pigs

Question 8

What are the different tissues that fill up the orbit?

Answer 8

Eye
Extraocular muscles
Blood vessels, nerves and connective tissue
Fat
Lacrimal gland, gland of TE and zygomatic salivary gland

Question 9

What can cause space occupying lesions in the orbit?

Answer 9

Infection or inflammation as abscesses or cellulitis
Neoplasia (normally malignant)
Specific tissue inflammation - extraocular polymiositis
Parasites

Question 10

What are the clinical signs of space occupying lesions?

Answer 10

Globe displacement
Protrusion of the third eyelid
Change in facial symmetry

Question 11

What are the characteristics of globe displacement?

Answer 11

Frequently dorsolaterally but depends on position of the mass
Frequent anterior component - exophthalmos

Question 12

Why does protrusion of the third eyelid (TE) occur with space occupying lesions?

Answer 12

With exophthalmos
Mass displaces orbital fat
Passive third eyelid protrusion

Question 13

What is microphthalmia?

Answer 13

Small eye

Question 14

What are the causes of microphthalmia?

Answer 14

Small eye from birth usually bilateral and may be accompanied by other ocular defects
Through destruction of the ciliary body as a sequela to inflammation, pthisis bulbi, targeted surgical destruction or chemical ablation

Question 15

What is buphthalmia?

Answer 15

Enlarged eye

Question 16

What causes buphthalmia?

Answer 16

Increased IOP leading to globe stretching and other changes such as conjunctival and episcleral hyperaemia, corneal oedema, Haab’s striae, Zonular tears, corneal ulcer

Question 17

What is Haab’s striae?

Answer 17

Stretch marks due to breaks in Descemets membrane

Question 18

What cases zonular tears?

Answer 18

Overstretching of fibres due to lens displacement

Visible lens equator through pupil

Question 19

What causes glaucoma?

Answer 19

Increased IOP

Damage to the optic nerve head and neural retina

Question 20

What are the 10 layers of the retina?

Answer 20

1 epithelial

9 neural with rods, cones and ganglion cells

Question 21

What can cause primary glaucoma?

Answer 21

Inherited

Goniodysgenesis = abnormal iridocorneal angle

Question 22

What are the two forms of primary glaucoma?

Answer 22

Open angle which is common in people

Closed angel which is common in dogs

Question 23

What can cause secondary glaucoma?

Answer 23

Blood, fibrin, PIFMs, WBCs, Neoplasia
Inflammation - uveitis
Hyphema
Lens luxation
Intra-ocular/metastatic neoplasia
Trauma

Question 24

Which cat breed is predisposed to primary glaucoma?

Answer 24

Burmese

Question 25

What can cause secondary glaucoma in cats?

Answer 25

Uveitis FIV, FeLV, FIP, Toxoplasma Idiopathic

Question 26

What is the relevance of whether glaucoma is primary or secondary?

Answer 26

Long vs short term - only one eye affected if secondary and once treated medically might not recur The other eye - primary will affect both eyes at some point, long term monitoring/treatment will be needed Breeding - no worry with secondary, advise against if primary

Question 27

What are the clinical signs of glaucoma?

Answer 27

Mid-dilated non-responsive pupil +/- aniscoria Conjunctival and episcleral vessel congestion +/- vision problems (negative menace/vision maze test) High IOP on tonometry

Question 28

What are the clinical signs of high to very high IOP?

Answer 28

``` Corneal oedema Haab's striae Cupping of optic nerve head Lens displacement Aphakic cresent Corneal ulceration ```

Question 29

What is aphakic crescent?

Answer 29

Crescent shaped gap due to tear of the zonules and lens movement away from it Development of crescent between pupil and lens

Question 30

What is the treatment for glaucoma?

Answer 30

Control of IOP using anti-hypertensive drops If secondary treat inflammation, remove the lens from the anterior chamber surgically, remove the eye with problem tumours

Question 31

What are the different anti-hypertensive drops that can be given?

Answer 31

Beta-blockers = Timolol Carbonic anhydrase inhibitors = Dorzolamide Prostaglandin analogue = Latanoprost

Question 32

What is the rationale behind using beta-blockers to treat glaucoma?

Answer 32

Reduce production of aqueous Give BID Weak but cardiac and respiratory effect

Question 33

What is the rationale behind using carbonic anhydrase inhibitors to treat glaucoma?

Answer 33

Reduce the production of aqueous Block CA enzyme in the ciliary body epithelium Given BID to TID Strong, work well in combination with beta-blocker (Cosopt) Works in cats and horses

Question 34

What is the rationale behind using prostaglandin analogues to treat glaucoma?

Answer 34

Increases the outflow of humour Given SID in the evenings or BID Strongest but can cause inflammation Doesn't work in cats, works in horses

Question 35

How is glaucoma managed?

Answer 35

Hospitalisation with serial measurement of IOP every 3 hours to plot a curve

Question 36

What are the clinical signs of lens luxation?

Answer 36

``` Phacodeonesis-Iridonesis - lens and iris wobbling Anterior presentation of vitreous Deep anterior chamber Anterior or posterior luxation An increase in IOP ```

Question 37

What are the causes of posterior luxation?

Answer 37

Cataract formation Lens induced uveitis Lens adhesion to the retina

Question 38

What are the consequences to anterior lens luxation?

Answer 38

Pupil block glaucoma | Damage to the corneal endothelium - central corneal oedema

Question 39

Which breeds are affected by inherited lens luxation?

Answer 39

Terrier breeds | Lancanshire heelers, Chinese crested, Australian Cattle Dog, Volpino Italiano

Question 40

What pathology does pupil block glaucoma and other acute increase in IOP cause?

Answer 40

Damage to retinal ganglion cells Damage to optic nerve head Damage to blood vessels possible

Question 41

What is the treatment for pupil block glaucoma and other acute increases in IOP?

Answer 41

Immediate removal of the lens in anterior luxation | Medical therapy to control future IOP spikes

Question 42

What is used in the medical management of lens luxation?

Answer 42

Xalatoan - PG analogue (causes marked miosis)

Question 43

What is the name of the surgical treatment for lens luxation?

Answer 43

Endolaser cyclophtocoagulation

Question 44

What are the three typical signs of retrobulbar disease?

Answer 44

Displacement of globe, 3rd eyelid protrusion, change in facial symmetry, corneal ulcer

Question 45

What causes aphakic crescent?

Answer 45

Increased IOP, zonules break, lens displaces, see equator

Question 46

What test would confirm high IOP?

Answer 46

Tonometry

Question 47

Is glaucoma painful?

Answer 47

Yes

Question 48

Does glaucoma affect vision?

Answer 48

Yes as it damages the retina and optic nerve head

Question 49

What is an IOP curve?

Answer 49

Measurement of the IOP every 3 hours and plotted on a graph to see when it spikes