Small animal Ophthalmology Flashcards
What makes up the uvea?
Iris
Ciliary body
Choroid
Path of aqueous humour?
Produces constantly by ciliary body
Drains through pupil into anterior chamber
Drained by drainage angle through pectinate ligaments
Determines intraocular pressure
Eye anatomy photo
Anterior space = between cornea and iris
Tarsal plates with tarsal glands
Conjunctiva lines lid and reflected back onto eye surface and continuous with cornea epithelium
Tapetum occupies upper half of back of eye sat behind retina
Retinal veins anastomose on surface of optic disc
What is the third eyelid? Appearance? Function?
Giant fold of conjunctiva Underside very hyperaemic due to lymphoid follicles May be pigmented Functions: - produces a part of the aqueous part of tears - surface protection - tear film distribution - immunological
Which animals don’t have a tapetum?
Pigs and rabbits
Horse eye anatomy differences?
Optic nerve more ventral - tapetum never reaches optic nerve
Eye flattened - not spherical
Retinal blood supply only around optic nerve (need rest of supply from choroid)
Granula iridica at top (and bottom) of pupil
Pectinate ligaments laterally and medially (grey lines) = drainage angle of aqueous
Ruminant eye anatomy differences?
Massive retinal blood vessels
Flattened eye
Bright tapetum
Rabbit eye anatomy differences?
Optic nerve head more dorsal
Massive retina and lens
Retinal blood vessels only run horizontally (may see choroidal vessels above and below)
Tooth roots in orbits
How does the pupil constrict and dilate?
Circular constrictor muscle - parasympathetic control (split into two parts in cats, medial and lateral parts stay put in horse)
Radial dilator muscle - sympathetic control
What is a mitotic and mydriatic drug?
Mitotic = constricts pupil Mydriatic = dilates pupil
What disinfectant is safe for the eye? Why antiseptic solution, not a surgical scrub solution? When would you just use saline?
Non lathering povidone iodine 1:50
Chlorhexidine is an irritant
Surgical scrubs are lathering
Saline if perforated eye as iodine is toxin to inside of eye
What suture material to use for eyelid surgery?
Absorbable
E.g. 5/0 vicryl in dogs, 6/0 vicryl in cats
What is the function of the tarsal plates? Benefit for eyelid surgery?
Stiffens the lid marginal areas
Contains tarsal glands
Secretes lipid portion of tears
Hold sutures much better than adjacent tissues
What is distichiasis? Is it a problem? Treatment options?
Hairs growing in an abnormal site from the tarsal glands within the tarsal plate and emerging at the lid margin Don't cause ulcers, some dogs not bothered but some are and need treatment No easy treatments Treatment options: - plucking - electrolysis - cryo - tarsoconjunctival resection
What are ectopic (conjunctival) cilia? Are they a problem? When to suspect? Treatment?
Emerge from the conjunctival surface and impinge directly on the eye (tiny stubble like hair)
Less common than distichiasis but far more painful and do cause shallow ulcers
Beware in young dogs (especially bulldogs) with a severely painful closed eye and no obvious cause
Treatment: easy - cut out! Good prognosis
What is entropion? What problem can it cause? Treatment?
In rolling of the lid margin so skin hairs impinge on eye (trichiasis)
Lateral 2/3 of eye margin - look for loss of lid margin
Can cause large masses of granulation tissue on eye with chronic hair contact - prognosis good once abrasion is removed
Entropion can be intermittent - test by turning lid in and see if dog flips it back
Treatment:
- skin and muscle excision (Hotz-Celsus procedure)
- lift lid up with finger
- first incision 2mm away from margin, second 3-5mm away tapered at both ends
- place middle suture first
- place deep suture if think area will be permanently wet to prevent wound breakdown (uncommon, lids heal well)
- degree of ectropion post-op is desirable, sorts out after couple of weeks
Define trichiasis?
Hair rubbing on eye
Should you clip for eye surgery?
Enucleation - full surgical clip
Eyelid surgery - surgical field only
Corneal, conjunctival or third eyelid surgery - no clipping
Innervation of the eyelids?
Orbicularis oculi muscle (VII nerve) encircles the lid margin to close the eye
Levator palpebrae superioris muscle (III nerve) and Muller’s muscle (smooth muscle, sympathetic) - raises upper eyelid
Why are SharPeis special? When to intervene?
Upper and lower lid problems
Can show lower lid entropion at a very early age
Downward angle to upper lid lashes due to convexity of the lid (most common problem in older SharPeis)
Excision surgery not advised in young puppies as may overcorrect
Can use tacking sutures as temporary measure until mature - but cut in and migrate away
When mature most need skin-muscle excisions on all four lids
What is ectropion? Problem?
Out turning of lid margin with conjunctival exposure
Mostly not a problem
Extreme = diamond eye - can result in entropion on upper and lower lateral edges - need to correct to get hairs out of eyes
What is upper lid trichiasis/entropion? Is it a problem? Treatment?
Not true entropion but definitely trichiasis
“Middle aged cocker spaniel upper eyelid syndrome”
Laxity of upper lid lashes which turn downwards and abrade eye causing discomfort and debility
Need Stades procedure rather than standard skin-muscle excision (not day one skill)
Eyelid “warts”/papillomas - significance?
Common and may remain unchanged for years
Check inside of lid and watch for growth and change
What is the most common eyelid tumour in the dog? Significance? Treatment?
Sebaceous adenoma/epithelioma
Arises from tarsal glands
Well defined mass requiring minimal clearance
Very low metastatic potential
Can bleed/ulcerate/irritate
Treatment - full thickness excision (check inside of lid):
- aim for perfect eyelid margin apposition
- knots must never contact the eye
- pentagonal by incising either side of tumour and then create a point or V incision if small
- remove as little lid margin as possible
- engage tarsal plate with at least one suture
- don’t use sliding grafts
- suturing conjunctiva as a spare layer risks knots contacting the eye - figure of 8 suture better at top and then simple interrupted
Significance of persistent scratching of the eye with periocular hair loss?
May be pruritus rather than eye pain
Scratching not common clinical sign for eye pain
What is cherry eye? Which breed mainly? Treatment options?
Prolapse of the nictitans gland of the third eyelid Mainly bulldogs Burying but preserving the gland (pocket technique): - preserves function - relatively expensive - failure rate Excision of the gland: - cheap - comes with guarantee won't come back - 30% of aqueous tear capacity lost
How to do the pocket technique for cherry eye?
2 curved incisions around gland and sutured over it
Adequate depth of the incisions to give a secure suture line (mucous membranes alone is too thin)
Blunt dissection through the incision closer to the eye to create some space for the gland
Strip a small area of conjunctiva off the apex of the swelling to allow adhesions to form
Tie first knot on outside
Problems with the third eyelid? Can you excise the third eyelid?
Cherry eye
Scrolling of the cartilage - far less common
Foreign bodies trapped underneath - turn out and removed (LA or sedation)
Only justified to excise third eyelid for neoplasia (especially cats, do badly without)
What conjunctiva of the eye is there? Normal colour?
Palpebral and outer third eyelid conjunctiva - dense pink Bulbar conjunctiva (covers globe) - white with discrete blood vessels
Normal appearance of eye mucus?
Off white-grey and darkens with time (may dry as black crusty lumps)
May accumulate in large amounts in dogs with deep medial pockets
Non specific conjunctivitis appearance? Treatment?
Diffuse redness without corneal, pupil or vision changes
Antibiotic responsive
Clears up in a few days
Never use oral antibiotics
Don’t do C+S
Occasionally do a snip biopsy of ventral conjunctiva in difficult cases
Fusidic acid - only effective against Staph
Broad spectrum drops
If persists then must be:
- something keeping it going (most commonly due to dry eye)
- or not conjunctivitis
Causes of a red eye?
Conjunctivitis Corneal ulcer or trauma Glaucoma Dislocated lens Uveitis Dry eye
Causes of dry eye in the dog? Which one causes the majority and how does it present?
Immune mediated inflammation of the glands with secondary loss of function (majority) - natural untreated pattern is gradual decline in tear values Sulphonamides Neurological (dry eye-dry nose syndrome) Trauma Distemper Chronic conjunctivitis/lid abnormalities Endocrine abnormalities
What produces and drains the tears?
Lipid part - tarsal glands
Aqueous part - lacrimal and third eyelid glands
Mucus part - conjunctival goblet cells
Tear duct openings on inside of medial upper and lower lids (lower more important) - join to form single tear duct (elongated Y) to nose
Clinical signs of dry eye?
Chronic conjuncitivits Dull appearance of ocular surface Mucopurulent discharge - tenacious and adherent Discomfort Corneal ulceration Corneal vascularisation and pigmentation
Diagnosis/monitoring and treatment for dry eye?
Schirmer tear test strips put on lateral lower lid for one minute (hold lids together) 20mm +/- 5 = normal 15mm = minimum 10-15mm = moderate dry eye <10mm = moderate to severe dry eye Re-measure each time comes in
Tear stimulants (for life):
- optimmune licensed (expensive, takes 3-4 weeks to reach maximum effect)
- tacrolimus skin ointment (expensive tube but lasts 6 months)/drops
Tear film replacements (poss for life):
- carbomer gel
- viscotears
- artelac nighttime gel
Reduce cyclosporin/tacrolimus treatment very cautiously (problem doesn’t usually go away)
What is follicular conjunctivitis?
Numerous lymphoid follicles appear as circular raised pink swellings especially in the ventral fornix
Relatively mild condition with mild or no irritation only and no purulent discharge
Aetiology etc uncertain
What does poor lacrimal drainage of the eye cause? How to test? What to do if not draining?
Painless “wet eye”
Fluorescein drainage test
Flushing:
- local anaesthetic +/- sedation
- flush upper duct first, watch lower duct
- nose down, VN on nose watch
- then occlude lower duct and flush again to test flow to the nose
Tear ducts may be non patent - can cut open (but painless problem so not essential to fix)
What is the cornea? Layers?
Transparent window, continuous with sclera
4 layers: epithelium, collagen, endothelium, descemet’s membrane
What is a corneal ulcer? are they important? Do they heal well? what can it progress to?
A full thickness defect in the epithelium
Must take seriously as cause pain and potential for progression
Corneal epithelium heals rapidly if favourable conditions - heals from perimeter inwards
Corneal stroma (collagen) is susceptible to proteolysis/melting/keratomalacia by enzymatic destruction - turns superficial damage into a deep ulcer
Proteolytic enzymes may be released by:
- gram -ve bacteria
- inflammatory cells
- corneal cells
Enucleation needed if ulcer perforates (everything prolapses forwards, even if heals will have no vision)
Signs of a perforated corneal ulcer?
Sudden pain
Convex protrusion of brown/black tissue with overlying fibrinous material
Blood from the eye
Larger and more central is worse
Diagnosis of corneal ulcers?
Fluorescein = orange dye which turns green in alkaline conditions
Lipophobic so runs off an intact epithelium
Hydrophilic so adheres to exposed stroma
Flush with saline to avoid false positives (won’t flush it out of genuine ulcers)
Dark blue light helps
What does it mean if there’s a clear area in the middle of a corneal ulcer?
Descemet’s membrane doesn’t stain with fluorescein and doesn’t become oedematous so stays clear at all times
Worrying as very thin last layer of cornea - close to perforating
Causes of corneal ulcers?
Direct mechanical damage: eyelids, trauma, foreign bodies
Unhealthy superficial environment: dry eye, poor blink
Inherent corneal defects: indolent (boxer) ulcer
Unknown or multifactorial: brachycephalics
Which types of dog breeds have a higher incidence of corneal ulcers? Why are they worse?
Brachycephalics
Spread and deepen faster
Often require surgery
Potentially including enulcelation
Medical therapy for corneal ulcers? What not to use?
Topical antibiotics (q4-6h if needed):
- chloramphenicol if simple and non infected superficial ulcer (=prophylactic use): broad spectrum, safe for epithelial cells and good penetration, won’t work if pseudomonas
- ofloxacin if infected
- gentamicin if pseudomonas
- (fusidic acid licensed for conjunctivitis so higher on cascade but narrow spectrum)
Lubrication - covers exposed nerve endings so eye more comfortable
Systemic analgesia e.g. NSAIDs
Parasympatholytic for cycloplegia (as reflex uveitis -> pain):
- atropine most effective (contraindicated if dry eye as can exacerbate, use cyclopentalate instead)
- cyclopentalate
- tropicamide
- contraindicated if glaucoma
If need systemic antibiotics: tetracyclines (esp. if melting ulcer)
Serum if melting ulcer (and hospitalise, may need surgery)
Not:
- not topical steroids as can cause keratomalacia and inhibits healing
- not topical NSAIDs as delays healing
- not local anaesthetic for pain relief as only lasts 1 hour, toxic to epithelium and prevents blinking
When is corneal ulcer surgery needed? Methods?
May be required for deep ulcers - eye becoming fragile/weak due to stromal loss, risk of perforation
Specialist:
- conjunctival pedicle graft
- corneo-conjunctival transposition (strip of cornea, limbus and conjunctiva advanced over defect, better for future vision)
Third eyelid flap - may help in comfort and healing but mostly not necessary or not enough and interferes with monitoring
Advantages of natural healing (non surgical) for corneal ulcers?
Less painful
Better end result
Cheaper
Simpler
Why are blood vessels important for corneal ulcer healing?
They regress when healing is complete
Vascularised cornea does not get infected, melt or perforate
What are indolent “Boxer” ulcers? Presentation? Breeds?
= Spontaneous chronic corneal epithelial defects (SCCEDs)
Breeds - boxers, corgis, staffies
Epithelial only - no concavity/crater
Loose epithelium (under-run edges)
Stain well with fluorescin (runs under epithelium at edges)
Vascularisation varies from none to extreme
Very different treatments to normal corneal ulcer
Generally don’t get infected, deepen or melt
Don’t heal by themselves or with medical treatment alone, minor surgery always needed!
Only ulcer to ever debride!!
Surgery and treatment for indolent “Boxer” ulcers?
Anaesthesia - LA drops +/- sedation, or GA
Debridement to remove loose epithelia and disrupt hyaline layer
Use a cotton bud or scalpel blade (sedation needed), plus:
- nothing
- grid keratotomy: must be very fine scratches, barely visible
- diamond burr: can use contact lens for pain relief
- superficial keratectomy: heals very well, most scarring, most expensive, reserved for stubborn cases
- TKP
Cotton bud debridement only in cats as grid etc risks sequestrum
Supported by:
- topical b/s antibiotics plus lubricants
- contact lens
- third eyelid flap
Debridement must be thorough - rub firmly, and keep going until stops, if comes off it needs to come off
Only repeat if loose edges again
This is dangerous for stromal ulcers!
What are the two types of corneal foreign bodies?
Adherent to surface:
- shallow curvature
- embedded in/on surface with little penetration
- can be wiped off or squirted off with saline under LA
Intracorneal = thorns:
- easier with a reasonable amount protruding
- microsurgical problem in many cases
- needle(s) for removal (better than forceps)
What is pigmentary keratitis?
Common non specific response of the cornea to a variety of insults
Common in medial quadrant of brachycephalics
What is a dermoid?
A congenital malformation where a patch of skin grows on the ocular surface
Usually hairy - irritant to cornea so need to be removed
French bulldog speciality
What is pannus? Treatment?
Inflammatory and vascular tissue advances across the cornea always from the ventrolateral direction
Strong association with GSDs
Treatment: topical cyclosporin/tacrolimus or topical steroids
What is paracentral lipid dystrophy?
Painful fat deposition in eye
Not proven to be associated with hyperlipidaemia or any systemic disease (atypical peripheral lipid depositions may be associated with hyperlipidaemia)
Causes of uveitis?
Lots! Anterior uveitis more common than posterior
Spontaneous/idiopathic - rare in dogs, lymphoplasmacytic uveitis in cats
Deep or infected ulcers - reflex uveitis
Lens-induced uveitis (e.g. cataracts)
Corneal trauma/laceration
Remote sites of infection inc. pyometra
Post intraocular surgery
Specific intraocular infections - adenovirus in dogs (rare), FeLV, FeCoV, FIV?, TB in cats
Treatment for anterior uveitis?
Mydriatics (e.g. atropine) - relieve pain and reduce risk of adhesions
Topical steroids - reduce inflammation
Oral NSAIDs
What do uveal cysts look like and significance?
Look like little cannon balls
Most cases not significant
May affect vision
Ocular melanomas in dogs? Types? Behaviour?
Uveal - not much can do except enucleate
Limbial - debulk followed by cryotherapy (respond well)
Benign
Can cause pain and glaucoma as grow into eye
What is glaucoma? Significance?
Abnormal rise in intraocular pressure
Always a problem of aqueous flow or drainage (not overproduction)
Always serious because great pain and rapidly destroys retina and optic nerve
It is the ultimate reason for eye removal in most cases
Causes of secondary glaucoma? How bad it it?
Uncontrolled inflammation Tumours Trauma Anterior lens luxation Perforations Severe intraocular haemorrhage Chronic retinal detachment
Development of secondary glaucoma indicates the primary problem is out of control and is usually untreatable
