Flashcards in Problem solving - Red eye + CS Deck (73):
What are the 3 main steps in working through a red eye case?
- where, what, how
- treatment plan
Where might you see redness in the eye?
- conjunctiva/ episclera/ sclera
- third eyelid
- anterior chamber
- anterior uvea
- posterior uvea and retina with funduscopy
- retrobullar area (cannot see directly)
What is the uvea?
ANTERIOR: iris and ciliary body
What should you consider for how you get a red eye?
- whole eye and adnexa
- from outside to inside
What are the 3 most important things to consider for how you get a red eye?
- what structures are in the tissue i am thinking of?
- how would each tissue respond to insult?
- how would changes in one tissue affect the other tissues around it?
What could cause a red eyelid?
- skin, meibomian glands, conjunctiva
- hyperaemia/ swelling/ ulcers/ crusts/ loss of hair
- dermatitis (various causes)
- Meibomian gland (infxn, neoplasia, granuloma)
What are eyelids intimately associated with? 2
- tear film
(problem could be loss of protective effect, loss of oily part of tear film from meibomian glands, contact problem). Leads to:
What is the conjunctiva?
Mucous membrane lining the eyelids, TE, sclera. Ends at the limbus where the 'white' meets the cornea = the corneoscleral junction
Describe conjunctival BVs
- dichotomous branching
- very sensitive to surface irritation
- dilatation of BVs and separation of ECs --> hyperemia and oedema (chemosis)
- show with superficial dz
- caution: possibly also episcleral BVs
When do episcleral BVs show prominently?
- these are deep BVs
- show with intraocular dz
- caution: possibly also conjunctival BVs
What is the episclera?
- CT under the conjunctiva
- up to limbus
- different looking BVs with no dichotomous branching, larger, meander (curves), signal intraocular disease mostly (glaucoma and uveitis) or sometimes severe/ chronic surface irritation
What is the sclera?
- the true white of the eye
- fibrous tunic
- continuous with cornea via limbus
- collagen fibres and fibroblasts
- Emisaria (= holes for BVs and nn)
How can you get redness in the TE?
- same as for the conjunctiva
- many lymphoid follicles in bulbar side (also palpebral side, very prominent in young animals and allergies, accompanied by hyperaemia). Can --> follicular conjunctivitis
- T-shaped cartilage core (holds TE against eye, can curl and cause an outward fold)
- contains lacrimal gland (30% tear film aqueous part), can prolapse + inflammation --> cherry eye)
- BVs are dichotomous and branching (n.b. TE doesn't have episcleral BVs).
List the 4 corneal layers
stroma (thickest part, hydrophilic so uptakes fluorescein)
endothelium (contacts air, eyelids, tears, bacteria/dust)
where descemet's membrane doesn't uptake stain due to a herniation in it, usually corneal wound or deep ulceraiton
Outline corneal oedema pathophysiology
stroma portion is hydrophilic so if there is a problem with epithelium, stroma will swell. It is essentially stromal overhydration.
How does the stroma stay relatively dehydrated?
Though action of:
- endothelium (which actively pumps fluid back into the AC)
3 main methods of damage to cornea
- loss of epithelium
- damage to endothelium
- vascularisation (leakage) of stroma
Structures that define the AC
iris, lens, cornea (endothelium), conjunctiva, ICA
What fills the AC?
Outline flow of A.H.
from CB, into posterior chamber, through pupil to AC then out at ICA.
Name 2 dz affecting the AC
- Glaucoma (ICA closure/ clogging of the ICA -> decreases uveoscleral outflow and increases IOP)
- Uveitis : increases uveoscleral outflow and decreases IOP
Name the 2 parts of the anterior uvea
CB and iris
What is the posterior uvea?
Outline uvea structure?
mesh of blood vessels, pigmented
Other structures in the uvea
- mm (constricotr, dilator and CB mm)
- anterior blood ocular barrier (separates blood and aquoeous)
- tapetum lucidum
What happens if the blood ocular barrier (BOB) of the uvea is broken?
you can have recurrent uveal / eye problem for the rest of your life.
What happens if the uveal epithelium separates?
- leakage into AC of keratic precipitates, hypopion, hyphema, fibrosis
- leakage around lens known as 'snow banking'
What is adhesion of iris to anterior lens?
Preiridal fibrovascular membrane:
- grow over iris and in pale irises are visible as rubeosis
- may lead to blinding to blinding of the eye (hyphema)
- closure/blockage of ICA - a type of secondary glaucoma
Define rubeosis iridis
BVs on iris (i.e. neovascularisation of iris)
- FIP, FIV, FeLV
When might sudden decompression of the anterior uvea occur?
- anterior synechiae
- bleeding form iris and ICA (retrograde flow of aqueous followed by blood)
Define iris bombe
apposition of iris to lens or anterior vitreous, preventing aqueous from flowing from posterior to anterior chamber.
How do anterior synechiae form with sudden decompression?
Corneal perforation, iris and lens damage (bleeding, cataract). As FB falls off, it causes iris prolapse and an adhesion of the pupillary edge of the iris to the posterior cornea.
Why are anterior and posterior uvea often simultaneously affected?
they are continuous
when posterior and anterior uveitis occur together
bleeding into anterior segment of the eye
What might you see with posterior uveitis? 3
- hyphema into AC
- retinal detachment
What happens if there is bleeding into the posterior segment?
not called hyphema (unlike AC) but causes retinal detachment
How can there be inflammation and ifxn in retrobulbar area?
- tooth removal and elevator enters posterior segment
- stick injuries in dogs --> retrobulbar abscess
- middle ear abscess
- conjunctival FB that travels posteriorly
- haematogenous spread
- blunt trauma - bleeding
- parasitic disease
Which tissues can be affected by neoplasia in retrobulbar area?
- extraocular mm
- optic nn (meninges, CSF)
- SNS and PNS, sensory nn
- lacrimal gland
- zygomatic salivary gland
- CT (e.g. bones)
- nearby anatomy (soft tissue with incomplete orbits, sinuses)
What do retrobulbar area problems lead to? Which 4 lead to red eye?
- altered position of eye within orbit -> dry -> red
- altered relationship with eyelids -> red eye
- possible increased pressure around eye (mass effect) -> red eye
- swelling/ infxn of tissues around it, including conjunctiva -> red eye
- vision loss (ON)
- pupillary problems
- restriction of ocular movement
Name 3 ancillary ophthalmology tests
- IOP test
What do you use transillumination/slit examination for?
anterior segment (AS) visualisation
Uses of DO
- nuclear sclerosis vs. cataract
- looking at pupillary shape/symmetry
How can you look at the fundus?
IO (monocular and binocular)
When does an eye have a blue hue?
when corneal thickening causes collagen fibres to fall out of arrangement as photons of light cannot pass through as they normally would.
What can corneal oedema cause?
Define ectopic cilia
usually one hair in one location, often central upper eyelid on conjunctival side of eyelid, grows in towards eye
can be single, usually numerous, not an extra line of eyelashes as the name means in latin, actually fur, NOT eyelash that exits from a meibomian gland near the TE.
normal hair that is poking you in the eye
What is Fucithalmic?
a topical AB that contains fucidic acid (stops protein synthesis)
T/F: distichiae can cause corneal abrasions but rarely ulers
If a STT has a reading of 15mm/min with an eye with an ulcer, what would this indicate?
technically this falls within normal limits for tear production, however an eye with an ulcer should have increased tear production, therefore this reading (especially as it is on the low end of normal), may indicate a problem
If there is positive uptake of fluorescein by ulcer walls and ulcer beds, which ddx can be eliminated?
How do cocker spaniels and weimeraners/ bulldogs differ in distichiae?
COCKER SPANIELS: long soft distichiae, may not cause (much) irritation
WEIMERANER/ BULLLDOG: short, stiff hairs, likely to cause irritation
Tx - distichiasis
* electrolysis - a current comes out of a probe --> radicals that destroy hair follicle epithelium
- wedge resection (but likely too many hairs, only really for ectopic cilia)
What is the commonest form of KCS?
primary immune-mediated KCS, can be uni/bilateral
T/F: dogs aren't particularly sensitive to FBs in the eye
True - their corneas aren't particularly sensitive (cats more so).
When might corneal oedema be seen?
epithelial disease or endothelial disease. endothelial disease may be caused by glaucoma or uveitis. IOP tanometry to differentiate.
Ddx - ulcerative disease in (young) dogs
- ectopic cilium of upper eyelid
- FB trapped under TE
- primary ulcers: SCCEDs
When might you perform surface ocular cytology?
when you suspect LPI (pannus), perhaps with an obvious cellular infiltrate (white/yellow abscess)
If a descemetocoele is present, what should you do?
Refer, don't attempt to sample for surface ocular cytology
When to perform surface culture and sensitivity?
with a melting cornea or a corneal abscess. DON'T sample with descemetocoele.
Medical tx for KCS
- Optimmune (BID)
- preservative free viscous tears
oculus uterque = both eyes
oculus dexter = right eye
oculus sinister = left eye
Sx - peripheral ulcer
conjunctival pedicle grafting
Sx - central ulcer
corneolimboconjunctival transposition (CLCT)
Why might atropine be bad to give to cats?
foul taste - cats are very sensitive to this and foam at the foam where food accumulates on lips/chin, huge volumes. In cats, give as ointment rather than injection to decrease the risk of it entering the mouth
T/F: anything you put in the eye can delay ulcer healing
True - especially preservatives