Equine Opthalmology Flashcards
How can you routinely examine the equine eye?
- Distance
- Local blocks
- Fluoroscein/ Rose Bengal dye
- Focal light source
–Pen torch or transilluminator
- Direct or panoptic ophthalmoscope
- Transpalpebral ultrasound
Name 2 examining techniques that are rarely used to examine the eye (3)
- Indirect ophthalmoscopy
- Slit lamp evaluation of cornea/anterior chamber
–Can be used
•Tonometry
How would you do lacrimal nerve block?
•Needle subcutaneously just dorsal to the lateral canthus
–direct medially across the dorsal orbital rim during injection
How would you do an Infratrochlear nerve block (2-3ml)?
–Insert needle at medial canthus
–Needle directed along the bony notch on the dorsal rim of the orbit (toward the medial canthus)
•Desensitisation of medial eyelid
Why would you do an infratrochlear nerve block?
- Desensitisation of medial eyelid
- Third eyelid remove
- Medial canthus eye laceration repair
How would you do a Zygomatic nerve block?
–Local anaesthetic along the ventral and lateral aspect of the bony orbit
•near the junction where the orbit begins to curve upward
What is a Zygomatic nerve block good for?
•Desensitisation of the remainder of the lower lid
What 3 things might we look for in a pre purchase occular exam?
–Evidence of congenital/hereditary ocular disease
–Diseases that may lead to decreased vision
–Tumours (SCC)
What is the uvea made up of?
–Iris
–Ciliary body
–Choroid – blood supply to retina
Why is the uvea important?
–Sight-limiting and a major cause of blindness if not appropriately diagnosed and aggressively treated
What equine uveitis do we see in the UK?
–Secondary to trauma
–Can be IM due to a variety of infectious organisms
What pathogenesis of uveitis do we see in USA and Europe?
–Equine recurrent uveitis
•Leptospirosis pomona/ grippotyphosa
Name 2 breeds susceptible to Equine recurrent uveitis (3)
–German WB’s
–Appaloosas
–Coloured horses
Name presenting signs of equine uveiitis
- OCULAR PAIN
- Excess lacrimation
- Blepharospasm
- (Photophobia)
- MIOSIS
- Fibrin in anterior chamber
- Corneal oedema
- Chorioretinitis
Name possible sequential events of equine uveitis
- Synechiae
- Iris rests
- Change in iris pigmentation
- Reduction in size of corpora nigrans
- Cataracts
- Retinal detachment
- Glaucoma
- BLINDNESS
What are the aims of equine uveitis treatment?
–Provide analgesia
•Ocular conditions are VERY painful
–Preserve vision
–Prevent or minimise recurrence
How can we treat equine uveitis? And why
•NSAID’s
–Systemic
•Atropine
–Topical
–Decreases pain when miosis reversed
–Decrease risk of synechiae and iris rest formation
•Corticosteroids
–With care
–NEVER if there is an ulcer
•Antibiotics
–Topical and BS
–Esp if using C/S’s
What is the prognosis with equine uveitus?
- Good if treated swiftly and aggressively
- Warn clients that there may be a recurrence
–Can’t predict which horses
•Any changes visible in the eye of previous uveitis will cause the horse to be failed at PPE
What is fibrin in anterior chamber ofte secondary to?
Blunt trauma
C) What is hypopyon (inflam cells in anterior chamber) usuallt secondary to?
B) What do they have concurrent?
A) Sepsis
B) Uveitis
Where is hypopyon common?
Farm and neonates
What are the 2 types of cataracts?
- Congenital
- ACquireed
What is the common caue of lens luxation and subluxation?
Trauma
When do we consider surgery with congenital cataracts?
–Cataracts
–No uveitis
–Intact retina
- PLR/menace
- Normal on U/S
–Vision impairment
–Appropriate personality
Congenital cataracts:
A) Uni or bilateral?
B) What can it be associated with?
A) Bilateral
B) Microphthalamus
What surgery is done on congenital cataract?
Phaecoemulsification
ACquired cataracts:
A) What is it often secndary to? (2)
B) What do we also see in older horses?
A) Uveitis and trauma
B) Nuclear lendicular sclerosis
Discuss the use of surgery in acquired cataracts
–Controversial for animals that have cataracts secondary to uveitis as prone to developing post-op complications
–Sight-limiting
•May wait until bilateral
–Risk of anaesthesia/recovery
–ERG and U/S useful to evaluate the retina if do
Name 2 hereditary disorders of the retina (2)
- Retinal colobomas (means absence of normal tissue)
- Congenital retinal detachments
- Chorioretinitis
What is Chorioretinitis secondary to?
In –utero infection with EHV-1
How may EHV 1 chorioretinitis manifest?
–Bullet-hole lesions in retina (non tapetal area)
–Few OK
–Many – may restrict vision
What lesion is seen with chorioretinitis?
•Bullet-hole or larger ‘butterfly-shaped’ lesions
What can be seen in the eye of EMND (equine motor neurone disease)?
•Retinal pigment epithelial cell accumulation (ceroid lipofuscin)
Name 2 things causing retina detachment (3)
- UVEITIS
- Trauma
- Penetrating ocular wounds
Name 3 causes of atrophy of the optic nerve (5)
–UVEITIS
–Trauma
–Glaucoma
–Toxicity
–Blood loss
What can cause Ischaemic ON neuropathy with the optic nerve (2)
–Int carotid occlusion for tx of GPM
–Blood loss
What causes vitreal opacities (2)
–Fibrin
–Porphyrin metabolites (blood)
What are secondary issues of vitreuitis? (2)
–Cataracts
–Traction bands (Tugs retina and detachs)
What can cause vitreal floaters? (3)
- Age change
- Secondary to uveitis
- Can result in head-shaking in a V small proportion of horses
Normal retina:
A) What are the vessels?
B) What colour is the optic disc?
C What colour is the non tapetal fundus?
D) What colour is the tapetal fundus?
A) Paurangiotic
B) Pink
C) Dark brown
D) Yellow to green
Name 5 diseases of the eyelids, third eyelid, cornea and aqueous (9)
–Eyelid injury and entropion
–Congenital abnormalities
–Eyelid neoplasia
- Sarcoids
- Melanoma
- Squamous cell carcinoma
–Habronema
–Ulcerative keratitis
•Bacterial
–Corneal abscess
- Keratacomycosis (fungal keratitis)
- Other keratitis – eosinophilic etc
–Viral keratitis (non-ulcerative / punctate keratitis)
–Glaucoma
How do we examine the equine eye?
- Sedation
- Perineural analgesia
Discuss the normal foals eye
–Low tear production
–Provide lubrication in the critically ill neonate
–Slow PLRs for first 5 days
–No menace for first 2 weeks
–Hyaloid artery remnants (hours)
–Prominent Y shaped sutures on lens
–Reduced corneal sensitivity
How can we take diagnostic samples of the eye and what do we use these for?
–Swabs
- Superficial bacteria (culture and sensitivity)
- For rapidly progressive, deep ulcers or treatment failure
–Scrapes
- Bacteria superficially
- Fungal disease (lives on descemets membrane)
–Biopsy
- Fungal disease
- Viral/immune mediated disease
Fluorescein:
A) What stains?
B) What does it confirm?
A) Corneal stroma
B) Epithelial defect/ulcer
Rose bengal:
A) What does it identify?
–Identifies defects in pre-corneal tear film
–Mucin defects
- Early fungal disease (multifocal lesions)
- USE IN THE ACUTELY PAINFUL EYE
How can you do tonometry in the horse?
Finger
Digital
What are the common diseases of the foal?
•Corneal ulcers
–Reduced sensitivity
- Uveitis – severe sepsis
- Congital abnormalities
–Microphthalmos
–Persistent pupillary membranes
•Require no intervention – rarely affect vision
–Congenital cataracts
•Require surgery
–Congenital glaucoma
–Dermoids, lacrimal punctae agenesis
Entropian in foals:
A) What is it commonly secondary to?
B) What does it requre?
C) What should you check for and how?
A) Dehydration and emaciation
B) Place a horizontal mattress
C) Stain for ulcer
Melanomas:
A) Where is it common?
B) How can we treat?
A) Grey horse
B)
- Excision, lid reconstruction and cryotherapy
- Enucleation
What is the most common eyelid neoplasia?
Sarcoids
What are the 5 types of periocular sarcoids?
–Nodular
–Verrucose
–Fibroblastic
–Occult
–Mixed
How might we treat periocular sarcoids?
–Topical brachytherapy Iridium wires 98% success
–Intralesional therapy with BCG 100% non recur
»± debulking ±5 fluoro-uracil
–Surgical excision – 50% non recur
–5FU – 67% non recur
What is the pathogenesis of squamous cell carcinomas?
–UV light –
–Increases with age
–Breed susceptibility
What is commonly affected with a squamous cell carcinoma?
Third eyelid
What is a differential for squamous cell carcinoma?
- Other neoplasma
- Parasite
What is the long term prognosis of squamous cell carcinoma?
–Rarely metastatic
–High long term recurrence
–Often require multiple therapies
How can we treat squamous cell carcinomas?
- Surgical excision – 50 % non recur
- Immunotherapy BCG – ??
- Chemotherapy – Cisplatin – 70% non recur, Mitomycine
- Cryotherapy – 50-100% non recur
- Brachytherapy – iridium – 90% non recur
What lesions are seen with Habronemiasis? Where?
•Granulomatous lesions associated with granuloma in medial canthus
How can we treat Habronemiasis?
–Ivermectin
- Systemic NSAIDS
–Fly control
What is the healing like with conreal disease?
Slow
What is a melting ulcer?
Proteinases within PCTF (MMP9 and neutrophil elastase)
- Normal defence / repair (PMNs, epithelial and stromal fibroblasts)
- Production stimulated by bacteria and fungae
- Proteinases produced by some bacteria
- Collagenases produced by some pathogens
- Grey liquefying appearance at edge of ulcer
What is the normal defence/repare of melting ulcer?
»Production stimulated by bacteria and fungae
»Proteinases produced by some bacteria
»Collagenases produced by some pathogens
Name common pathogens of the cornea
- Staphyoloccus
- Streptococcus
- Pseudomonas
- Aspergillus
- Fusarium
- quine Herpes Virus
How do you deal with corenal ulceration?
- Should receive prompt aggressive treatment
- Infection should be considered in all ulcers
- Concurrent uveitis should be addressed
What are the clinical signs of corneal ulcer?
•Slight pain
–Blepharospasm
–Epiphora
–Photophobia
–Mild drooping of eyelids
How do we diagnose corneal ulcer?
Stain
How do you treat corneal ulcer?
A) First line/simple
B) Melting ulcer
C) Alternative
A) First line / simple ulcers
•Broad spectrum topic antimicrobials
–All impair ulcer healing
- Chloramphenicol
- Fucidic acid (gram +ve)
- Triple anti-biotic (neomycin, gramicidin, polymixin B)
B) Melting ulcers
•Likely to involve pseudomonas
–Ciprofloxacin – Often resistance to gentamicin
C) Alternatives
•Ciprofloxacin (gentamicin resistant pseudomonas)
–Or chloramphenicol, polymixin B
•Cephalosporins for beta hemolytic streps
How can we control melting ulcers?
–Block collagenase activity (Pseudomonas and beta hemolytic streps)
•PLASMA (horses own) – BETTER THAN SERUM
–Anti-proteinase activity
–Fresh every 5 days
•EDTA
–Binds calcium
•Acetylcysteine
–Can combine 2 or 3 for severe ulcers
–Consider hourly medication for first 12-24 hours
How do you treat uveitis?
–Consider in all cases
–Topical atropine
–Systemic NSAIDS
How do fungal ulcers cause issues?
•Usually colonisation of ulcer with commensal fungae
–Plant material
- Proteinase release
- Anti angiogenic
- Affinity to Descemets membrane
How can you treat fungal ulcers?
Topical
–Miconazole, itraconazole,
–May exacerbate uveitis initially
•Fungal death
What is the benefit of bandaging contact lenses?
–Maintain apposition of healing ulcer
–Reduce pain
–Protection
What is conjunctival pedical flaps used for?
–Deep melting ulcers
–Large superficial ulcers
–Corneal perforation
Name 4 surgical therapies for an ulcer (6)
- Bandage contact lense
- Debride
- Conjunctival pedical flaps
- Third eyelid flaps
- Temporary tarsorrhaphy (suture eyelids shut)
- Amniotic membrane flaps
Glaucoma:
A) What is it seen as a sequelae to?
B) Name clinical signs?
A) Uveitis
B)
–Dilated pupils
–Corneal band opacities
–Uveitis
–Optic nerve atrophy
–Poor vision
Name 2 methods of preventing treatment failure (4)
- Use solutions sprayed using an insulin needle
- Lavage systems
- Subpalpebral lavage systems
- Nasolacrimal duct catheters
How can we diagnose Superficial punctate keratitis?
–Subtle fluorescein staining
–Rose bengal retention
–Slit lamp (even on ophthalmoscope) can be useful
How can we treat Superficial punctate keratitis? (3)
–EHV-2 implicated
–Topical antivirals
–Topical NSAIDS
Where are Subpalpebral lavage devices placed?
Dorsal or central fornix
What is the last resort option for a resistant ulcer?
Enucleation
Which nerve block is this?
Lacrimal nerve block
Which nerve block is this?
Infratrochlear nerve block
Which nerve block is this?
Zygomatic nerve block
What are these? What is the relevance?
Iridic granules
Horse has these which sit coming down from dorsal part or up from ventral of the iris
These should be the same on both eyes and roughly the same size –otheriwe you would question pathogenic
“sunglasses” for horses stop light hitting to the optic disc which sits ventral to the fundus
What is this and what is the rlevance?
Normal retina assessment
Looks different to other species
Usually have the big y shape vessel supplying optic disc
Have trapetal funfudus which depends on the coat colour
Non tapetal fundus 0 optic disc sits
Blood supply looks like a sunshine
Eye folds in embryological development –often blips in otic disc and see changes in non tapetal fundus.
Changes at 6 o clock – chances are this is okay
Label this eye ultrasound
- Retinochoriod unit
- Optic nerve head
- Cilaiary artery
- Extraocular muscle
- Retrobulbar fat
What is going on here?
Copra nigra with shape
Synechiae anterior
Blocks of iris rest
Scar on cornea surface (probs trauma)
What is going on here?
Cataract
Iis strand to right of lens (were posterior synechiea)
What is going on here?
End stage
Third eye visible – microphtlamic
Shrunk down eye – left with reticulated patten on surface
Pigment on the cornea secondary to inflammation
What is this?
Equine Uveitis
What is this?
•Fibrin in the anterior chamber
What is this?
Hypopyon
What is this?
Cataract
What is this?
•Retinal colobomas
What is going on here?
What do these show?
Chorioretinitis
What condition has this finding?
EMND
What do all these show?
Retinal detachments
What disorder is shown?
Optic nerve disorders
What is this?
Vitreitis
What is this?
What is this showing?
Perineural analgesia
Which stain is this?
Fluorescein
Which stain is this?
•Rose bengal
What can be seen?
What is this?
Cornea ulcer
