Equine Opthalmology

Question 1

What mydriatic should you use to aid fundic examination?

Answer 1

Tropicamide - duration - 4 to 6 hours

Question 2

What diopter should you have the ophthalmoscope set at for close direct opthalmoscopy at different levels in the equine eye?

Answer 2

0 to -3D - fundus
+2 to 6D - vitreous
+7 to +8D - lens
+10D - cornea

Question 3

What can a split lamp be used for?

Answer 3

Assessing the depth of lesions in the eye

Question 4

How can you perform the auriculopalpebral nerve block?

Answer 4

Blocks the motor fibres of the auriculopalpebral n. VII
Does not provide analgesia
Run the finger down the orbital rim and feel the nerve ping under your finger
Instil 5ml of local

Question 5

Describe the frontal / supra orbital nerve block

Answer 5

Provides analgesia to the eye
Supraorbital branch of V blocked
Palpation the the supra orbital process on the frontal bone, where the nerve emerges from the supra orbital foramen
Instill 2ml of local, then pull back slightly and inject another ml
Desensitises the middle 2/3 of the upper eyelid

Question 6

How does a superficial ulcer appear after fluorescein staining?

Answer 6

Sharp edges
No under running of the epithelium
No stain migration

Question 7

How does an indolent ulcer appear with fluorescein staining?

Answer 7

Epithelium is under run

Question 8

How do deep storm all ulcers stain with fluorescein?

Answer 8

Very intense staining, stain migration occurs in 5-15mins

Question 9

How do desmetocoeles stain with fluorescein?

Answer 9

Wall of the ulcer stains intensely

Central area with no stain uptake

Question 10

What does the seidel test demonstrate?

Answer 10

Aqueous leakage - stream of fluorescein where the aqueous is leaking

Question 11

What can rose Bengal stain be used for?

Answer 11

Assessing the tear film
Assessing the margins of conjunctival and corneal neoplasia
Fungal ulcers

Question 12

How can you take a cytology sample of the eye?

Answer 12

Cytology brush

Don’t put local anaesthetic on before - sterilises the eye

Question 13

What locations are associated with better prognoses with eyelid lacerations?

Answer 13

Lower eyelid better than upper eyelid

Lateral eyelid better than medial eyelid

Question 14

What is TOC for sarcoids around the eye?

Answer 14

Radiotherapy / brachytherapy

Question 15

What is the prognosis of eyelid tumours following surgery?

Answer 15

SSC - variable - follow up with chemo/RT

Melanoma - good

Question 16

What is the most common corneal problem in horses?

Answer 16

Ulcerative keratitis

Question 17

What are the clinical signs of ulcerative keratitis?

Answer 17

Blepharospasm
Epiphora
Pain
Photophobia

Question 18

What should you treat superficial ulcerative keratitis with in the horse?

Answer 18

Topical antimicrobials
Topical atropine - for reflex uveitis
+/- serum

Good prognosis if managed correctly

Question 19

How should you treat deep ulcers in the horse?

Answer 19

Prolonged course compared to superficial ulcers
Topical antibiotics
Topical atropine
Serum

Question 20

What is the pathogenesis of keratomalacia in the horse?

Answer 20

Activation of proteinuria enzymes in the cornea by epithelial cells, leukocytes and pseudomonas

Requires early aggressive therapy

Question 21

How should you treat keratomalacia?

Answer 21

Topical serum
Topical CaEDTA - chelates Ca so pro teases can’t activate
Topical acetylcystine - maintains the tear film
Topical tetracycline / doxycycline - inhibits MMPs
Flunixin

Question 22

How should you treat a descemetocole?

Answer 22

Flunixin
Atropine
Refer for surgery - conjunctival flap

Question 23

How should you treat a non-ulcerative keratitis/stromal abscess?

Answer 23

Atropine
Chloramphenicol - gentamycin is not adequate
Refer for surgery - debridement or corneal graft

Question 24

How does equine herpes virus 2 viral keratitis present?

Answer 24

Multiple, superficial, punctate ulcers

Variable staining with rose Bengal and fluorescein

Question 25

How can you treat this?

Answer 25

Topical acyclovir | Topical idoxuridine

Question 26

How is fungal keratitis diagnosed?

Answer 26

Cytology essential - sample deep into the cornea

Question 27

How can you treat fungal keratitis?

Answer 27

Voriconazole- antifungal of choice | Warn owners it is likely to get a lot worse in the first 24 hours due to the massive death of fungi

Question 28

How do immune mediated keratopathies usually present?

Answer 28

``` Insidious onset Unilateral No uveitis - not very painful Superficial - irregular corneal surface Deep - bullae formation, vascularisation and oedema ```

Question 29

How can you treat immune mediated keratopathies?

Answer 29

Medical management - topical corticosteroids, cyclosporine A, doxycycline Surgical - keratomy, cyclosporine a implant

Question 30

What are the clinical signs of anterior uveitis? | Iris and ciliary body

Answer 30

``` Blepharospasm Epiphora Chemosis Miosis Aqueous flare - leakage of lens proteins Hyphaema Hypopyon Fibrin in the anterior chamber ```

Question 31

What is clinical presentation of posterior uveitis? Choroid

Answer 31

Low grade ocular discomfort

Question 32

How can you treat uveitis?

Answer 32

``` Treat underlying cause Flunixin Topical corticosteroids if no ulcer Topical antimicrobials Topical atropine - care may cause colic and ileus ```

Question 33

What surgical options are available for the management of uveitis?

Answer 33

Suprachoroidal cyclosporine A implant Pars plana vitrectomy - only really for uveitis due to lepto Enucleation

Question 34

Signs to look for during a vetting to assess whether a horse has had uveitis in the past.

Answer 34

Atrophy of the granula iridica and irregular pupil margin Anterior synechiae - iris adhered to cornea Posterior synechiae - iris adhered to the lens Cataracts Glaucoma Blindness Retinal pathology Phythisis bulbi

Question 35

What are the two causes of cataracts in horses?

Answer 35

Acquired - uveitis, trauma, tumour Developmental - congenital in foals Most don't require treatment - not progressive and have little effect on vision Can be removed by phacoemulsification

Question 36

List the types of cataracts found in horses.

Answer 36

``` Capsular cataract Nuclear cataract Perinuclear cataract Equatorial cataract Sutural cataract Complete cataract ```

Question 37

What is the drainage angle in the horse?

Answer 37

Conventional angle - pectinate ligaments | Unconventional angle - big blood vessels in the ciliary body

Question 38

How can you diagnose glaucoma?

Answer 38

``` Hydrophthalmos Bupthalmos Corneal oedema Corneal striae Lens luxation Blindness ```

Question 39

How can you diagnose glaucoma?

Answer 39

Tonopen | Enlarged eye

Question 40

How can you treat glaucoma?

Answer 40

Dorzolamide - topical carbonic anhydrase inhibitor Timolol - beta blockers Flunixin Topical corticosteroids Prostaglandin derivative are CI in horses

Question 41

How can the colour of a retinal lesion indicate its depth?

Answer 41

``` Neurosensory retina - cling film Retinal pigment epithelium - black Tapetum - blue, green, Amber Choroid - red Sclera - White ```