21.10: Ophthalmology

Question 1

Corneal ulcer

Answer 1

break in continuity of the corneal epithelium with exposure of the underlying stroma.

Question 2

What is the difference between a corneal ulcer and ulcerative keratitis?

Answer 2

No difference - they are the same thing.

Question 3

1

Answer 3

Epithelium

Question 4

2

Answer 4

Stroma

Question 5

3

Answer 5

Descemet’s membrane

Question 6

4

Answer 6

Endothelium

Question 7

How is corneal transparency retained?

Answer 7

• No keratin, blood vessels or melanin
• Low cell density
• Very regular arrangement of collagen fibrils
• Relatively dehydrated state

Question 8

How is the relatively dehydrated state of the cornea maintained?

Answer 8

• Epithelium has tight junctions to prevent water from tear film entering
• Endothelium below has Na/K ATPase pump; this pumps ions from the stroma into aqueous humour

Question 9

What happens if water gets into the stroma of the cornea?

Answer 9

• Corneal oedema develops
• The collagen fibrils are distorted, resulting in opacity

Question 10

Superficial corneal ulcer

Answer 10

There is loss of the epithelium only.
* Cells slide rapidly over to cover the defect
* Within hours-days there is cell proliferation, migration and adhesion

Question 11

Describe the process of healing for a stromal ulcer

Answer 11

• This takes longer than a superficial corneal ulcer to heal
• The epithelium must grow over the deficit before the stroma can begin to heal
• Once re-epitheliasisation is complete, fibroblasts migrate in and lay down new collagen
• Requires vascularisation
• Results in scar tissue -> remodelling occurs over time

Question 12

What are some possible causes of corneal ulcers?

Answer 12

• Trauma
• Tear film problem (e.g. KCS)
• Adnexal conditions
• Primary corneal disease (e.g. SCCEDs)
• Infection
• Neuro disease

Question 13

What might have caused these ulcers?

Answer 13

These ulcers occurred secondary to keratoconjuctivitis sicca
* These ulcers have a circular ‘punched out’ appearance and deteriorate rapidly

Question 14

Answer 14

Entropion

Question 15

Answer 15

Eyelid mass

Question 16

Answer 16

Ectopic cilia

Question 17

Answer 17

Pug with macropalpebral fissure resulting in lagophthalmos and exposed cornea

Question 18

Answer 18

Shih tzu with triachiasis resulting from pronounced nasal fold

Question 19

Answer 19

Spontaneous Chronic Corneal Epithelial Defects which can cause corneal ulceration

These are especially common in Boxers and are often un-healing.
Only epithelium is lost but it fails to adhere to underlying stroma - reason unknown.
Recurrence a common ssue.

Question 20

Answer 20

Cat with corneal ulcer due to neurotropic keratitis

Question 21

Neuroparalytic keratitis

Answer 21

Facial nerve paralysis which results in inability to blink

Question 22

Neurotrophic keratitis

Answer 22

Trigeminal nerve problem where there is reduced or absent corneal sensation so the animal does not blink. This is highly likely to cause ulceration.

Rare.

Question 23

a) Brachycephalic conformation
b) Entropion
c) Distichiasis
d) KCS
e) FHV-1

Answer 23

B) Entropion
Seen in some older cats
Causes ulcers

Question 24

Which cranial nerves does the palpebral reflex test?

Answer 24

• Trigeminal - eyelid sensation
• Facial - blinking

Question 25

**True/false:** exposed Descemet's membrane will take up fluorescein stain.

Answer 25

**False!** Descemet's membrane does not take up fluorescein stain

Question 26

What are the clinical signs of corneal ulceration?

Answer 26

Question 27

Answer 27

Question 28

Answer 28

Question 29

**Descemetocoele**

Answer 29

Question 30

Answer 30

Question 31

**Keratomalacia**

Answer 31

Question 32

**True/false:** steroids are a good first line treatment for corneal ulcers.

Answer 32

**False!!!!!!!** Topical steroids cause local immune suppression and potentiate collagenase activity. Never use steroids with a corneal ulcer!

Question 33

Answer 33

SCCED

Question 34

Answer 34

L arrow = stromal ulcer R arrow = descemetocoele

Question 35

Answer 35

Melting ulcer

Question 36

Answer 36

Perforated ulcer

Question 37

What questions should you ask yourself when dealing with a corneal ulcer?

Answer 37

Question 38

Treatment of a simple superficial ulcer

Answer 38

## Footnote Avoid topical NSAIDs as these may delay healing.

Question 39

Treatment of SCCEDs

Answer 39

Question 40

Treatment of melting ulcers

Answer 40

Question 41

**True/false:** grid keratotomy is a good idea for a non-healing ulcer in the cat.

Answer 41

**False** Never grid a cat's cornea!

Question 42

Which of the following animals would have the best prognosis following a globe prolapse? a) Cat b) Greyhound c) Shih Tzu d) Spaniel

Answer 42

c) Shih Tzu

Question 43

Answer 43

**Retrobulbar abscess**

Question 44

In cases of glaucoma, we need to reduce IOP. What drugs can we use to do this?

Answer 44

* **Prostglandin analogue (e.g. latanoprost)** if suspeced primary glaucoma, not for lens luxation * **Carbonic anhydrase inhibitors (e.g. brinzolamide, dorzolamide)** always OK but may not be enough on their own * **IV mannitol used to be drug of choice but less so now** Also provide analgesia, seek referral advice or send animal there, consider referral assessment of the other eye because primary glaucoma = bilateral condition.

Question 45

What signs of glaucoma might we see on ocular exam?

Answer 45

Question 46

Answer 46

**Anterior lens luxation**

Question 47

Which animals cope better with anterior lens luxation - dogs or cats?

Answer 47

Cats cope better. Anterior lens luxation is an emergency in the dog!

Question 48

Differentials for sudden onset blindness

Answer 48

* Acute glaucoma * Acute uveitis * Intraocular haemorrhage * Retinal detachment * Optic neuritis * Sudden Acquired Retinal Degeneration (SARD) * Toxicity: ivermectin, enrofloxacin in cats * Intracranial lesion May need specialist equipment e.g. electroretinogram (ERG) or MRI to make diagnosis