Opthamology Flashcards
Persistent pupillary membrane
Foetal vasculature remnants that arise for the iris collarette and may stay in the iris of reach the cornea causing an opacity of either
Eyelid agenesis
Congenital
Abscess/cellulitis
Developmental
Strep or staph infection
Extra ocular polymyositis
Development Enlargement of the extra ocular muscles Bilated, very dilated pupil If not treated in time -> scarring -> permanently affected eye movement, optic nerve damage 2 weeks steroids
Blepharitis
Developmental
Trichiasis
Hairs from normal location contact the ocular surface
Not healthy for the eye - irritation to ulceration
Various causes
Distichiasis
Often multiple hairs - many present along eyelid margin of upper and lower eyelid
Arise from Meibomian glands
Ectopic cilium
Very irritating to cornea, frequently ulcerating, really early on
Usually associated with meibomian glands but do not ‘sprout’ through the gland opening
Come out through the conjunctiva of the bulbar surface of the eye and are nearly always located in the central upper eyelid of young dogs (
Ectropion
Developmental
Eyelid begins to fold out
Medial lower eyelid +/- canthus - brachycephalic dogs and cats esp pug
Upper eyelid - cockers, hounds etc. heavy eyes and forehead
Lateral upper and lower eyelid, lower canthus - Shar-pei
Lateral lower eyelid - young dogs, medium-to-big, old cats, blepharospasm
Dacryocystitis
Generally FB present but can be idiopathic
Idiopathic - unidentified debris
Infection of the lacrimal sac, secondary to obstruction of the nasolacrimal duct at the junction of lacrimal sac.
Pain, redness, and swelling over the inner aspect of the lower eyelid and epiphora.
Prolapsed gland of the third eyelid
Aka cherry eye - becomes inflamed
Developmental
LPI of the third eyelid
Lymphocytic-plasmacytic infiltrator if the third eyelid aka plasmoma
Developmental
Scrolled third eyelid
Part of T shaped cartilage grows excessively fast and folds
Corneal oedema
Developmental
Loss of epithelium - ulcer
Endothelial damage - increased IOP (glaucoma), inflammation (uveitis, low pressure), primary epithelial degeneration, contact (lens, surgery)
Vascularisation (developing vessels leak)
Corneal ulcer
Developmental
Fluorescein test
When corneal epithelium is missing
May develop red bed of granulation tissue
Corneal granulation tissue is formed by coalescing blood vessels (always arise at limbus and travel to trouble)
Eye muscles
Orbicularis - eyelid closure
Levator palpebral superioris - lift upper eyelid
Mueller’s muscle - supportive, upper eyelid
Nasolacrimal system
Blink brings tears back to medial canthus (puncta to collect tears)
Involves upper and lower punctum, canaliculi, lacrimal sac, nasolacrimal duct. nasal punctum
Jones test
Fluorescein drop on eye and wait for stain to come through nose
3rd eyelid/nictatins/nictating membrane
Leading edge cartiliginous core gland of the 3rd eyelid (30% tears)
Lacrimal gland
Below the dorsolateral orbital mm (70% of tear)
Subconjunctival tissues
Tennon’s capsule and the episclera (contain episcleral blood vessels - meander dont’ branch)
Episcleral vessal pattern
See typically with intraocular disease
Tear film
Lipid layer: on top, secreted by Meibomian glands, avoid evaporation of aqueous part
Aqueous layer: middle and most abundant, water, many solutes, defense mechanisms (immunoglobulin and lactoferrin)
Mucus layer: inner, secreted by corneal epithelial cells and goblet cells of the conjunctiva
Corneal epithelium
Few cells thick, most external layer
Basal cells in the deepest layer will ultimately shed as squamous cells in 1 week cycle
Basal cells act as stem cells
Cornea - Stroma
Thickest part
Several layers of collagen - each layer = lamella
Relative state of dehydration and GAGs keep orderly state of each lamella
Created by keratocytes
Corneal transparency
Achieved by lack of blood vessels and lack of myelin on corneal nerves
Cornea - Descemet’s membrane - surgical emergencies!
During progressive ulceration of the cornea, right before perforation this layer forms a descemetocele
Corneal endothelium
I cell thick layer
keeps cornea dehydrated - action of NaK-ATPase pump - takes fluid for aqueous humour -> stroma -> aqueous humour
Has almost no regenerative capabilities - limited ability to deal with cell loss
Sclera
White fibrous tunic, continuous with limbus and cornea - covered by subconjunctival connective tissue (episclera/Tennon’s capsule) and conjunctiva
Very thin near equator and optic disc
Several holes for nerve and blood vessels
Also contains the lamina - ribosa through which the axons of the ganglia exit the eye to form the optic nerve
Lamina Cribrosa
Hole in sclera which axons of the ganglion cells leave the eye to form the optic nerve
Synechia
Adhesions of the iris to other structures
Occur with inflammation of the iris - uveitis
Posterior synechiae - iris and lens
Anterior synechiae - iris and cornea, sudden loss of aqueous humour eg corneal perforation
Ciliary body
Has own musculature - focusing
When this musculature is contracted during disease can be source of pain
Has capacity to produce aqueous humour
NB involves action of carbonic anhydrase enzyme
Choroid - posterior uvea
Contain tapetum - reflects light inside the eye, better night vision, feeds outer retina (mostly the photoreceptors)
Horses have stars of Winslow all over tapetal fundi (end on capillaries that give tapetal fundus a subtle pin-prick spotted appearance)
Tapetum brighter in carnivores than herbivores
Iridocorneal angle
Outflow of the aqueous humour -> venous circulation (ultimately)
360 degree structure found between the iris and cornea
Zonules
Arise from ciliary body and attach to the lens. Anteriorly and posterior to the lens equator
Retinal epitheliam
Outermost layer
Retinal pigment epithelium (RPE) - nurses photoreceptors it is in contact with
Retina
9 neural layers
Outermost contain the photoreceptors, the rods and cones
Innermost layers contain the ganglion cells and the neural fibre layer which are an accumulation of axons - untimately form optic nerve
Retinal vasculature
Dogs, cats, farmed ungulates
Venules and arterioles that are generally paired
Dorsal, lateral and medial one - smaller ones branch from them
More subtle in horse
Optic nerve head, disc or papillae
Species differences
Various degrees of fluffy myelin
Dog: square/diamond shaped, anostomic branches of the retina on top
Cat: very round, no obvious myelin
Horses: oval, salmon colour
Vitreous body/gel
gelatinous structure fills large space in the psterior segment
Fundic reflex
Reflection of light we see coming back through the pupil
Usually yellow/green but can be orange
Red in atepetal animals
Pharmacology Mydriatic (short term)
Tropicamide
Pharmacology
Mydriatic/cycloplegic (long term)
Atropine
Pharmacology
Antibiotics
Fucidic acid
Chloramphenicol
Gentamycin
Fluoroquinolones (as Ciloxin and Exocin)
Triple antibiotic preparations:
e. g. neomycin, polymixin B, bacitracin
e. g. neomycin, polymixin B, gramicyclin (more common in USA)
Pharmacology
Steroids
Dexamethasone phosphate
Prednisolone acetate
Pharmacology
Immune-mediator
Optimmune
Pharmacology
NSAIDs
Flurbiprofen
Diclofenac
Pharmacology
Antihypertensive
Ca channel blocker (timolol - in Timoptic and Cosopt) Carbonic anhydrase inhibitors (dorzolamide - in Trusopt and Cosopt) Prostaglandin analogue (Iatanoprost)
Canine Lymphocytic-Plasmocytic Infiltrative
AKA corneal pannus, chronic superficial keratosis (CSK)
Especially greyhounds/lurchers, sunny/snowy countries
Cellular infiltrative and vascularisation +/- pigment
Dorsolateral corneoconjuctiva usually affected first
Primary immune mediated disease
Diagnosis: cytology
Treatment: Proxymetacaine 0.5% (topic anaesthetic)
-OOA: 30-60s
-DOA: 15-30mins
-Decrease blink, increase dryness, ulcer formation
Feline eosinophilic keratitis (EK)
also rabbits and horses
(Rabbits and horses)
Corneal inflammation with eosinophilic keratitis
Primary, immune-mediated, idiopathic
Fluorescein stain uptake - can be confused with ulcer
Dorso-lateral corneoconjunctival area normally affected first
Cellular infiltrate with: neutrophils, plasma cells, clusters of eosinophils - white/pink in the form of plaque/clumps - lumpy cottage cheese
Treatment of EK and LPI
Topical use of immune modulators 4xday
Taper after many weeks (week 1: 4xd, weeks 2-4: 2xday etc)
Lowest dose possible for long term maintenance
Canine dry eye (KCS - keratoconjunctivitis sicca)
Primary KCS:
History: recurring persistent ocular surface problems
Signs: conjunctivitis, surface dullness, mucus discharge, ulcers, low STT-1
Treat: topical ciclosporin bid/sid, long term, Optimmune, surgery (C;CT, conjunctival pedical graft)
Usually primary and bilateral
Acute: young and older dosg, less mucus and less hyperema
Chronic: scarring, pigment changes, vascularisation
Other causes: Evaporative, anaesthesia and sedatives, Drug-related (sulfonamide, atropine), Neurogenic (affected nerve supply to lacrimal gland)
KCS improvement
If positive changes in at least 3/5
- Mucus production
- Redness
- Comfort
- Keratitis
- Tear readings
Lipid infiltrate
Reflective white crystals in superficial stroma
Primary form: most common, no vascularisation, several breeds eg CKCS, huskies
Secondary: degeneration, vascularisation, associated with chronic corneal problems and hyperthyroidism
Might be removed if affecting sight - not painful
Usually slowly progressive
Calcium infiltrate
Chalky non-reflective white crystals in superficial stroma - may adapt reticulated pattern
Secondary: (degeneration) associated with chronic, corneal problems, accompanied by vascularisation
May need to be removed via keratectomy if painful - can spiculate -> breaks through epithelium - painful
Difficult to tell apart from lipid in early cases
Corneal scar
Associated with chronic keratitis, ulceretive keratitis and surgery
May be accompanied by residual vascularisation and pigment
Whitish discoloration: non-reflective, non-crystalline, dull
Corneal abscess
Accumulation of WBCs
Enzymes can lead to rapid collagen melting
Not a pocket of fluid - cannot be drained
Pigment keratosis - pugs
Associated with medial canthal and lower eyelid entropion
Overexposure of the cornea and conjunctiva (macropalpebral fissure: big space between the eyelids)
Occasionally associated with dry eye (KCS)
Can be sight impairing by 2yo