30. Microbial Keratitis Flashcards
Every ...
causes an ...
, but not every ...
is infectious.
Every infection
causes an infiltrate
, but not every infiltrate
is infectious.
The cornea is an immune ...
environment due to being ...
and ...
. ...
represent an immune response to a corneal insult. In response to an evading pathogen or insult, the corneal epithelial cells release ...
and ...
. Immune cells are released from ...
. The ...
is an aggregation of ...
, ...
and ...
as part of the inflammatory response.
The cornea is an immune privileged
environment due to being avascular
and alymphatic
. Corneal infiltrates
represent an immune response to a corneal insult. In response to an evading pathogen or insult, the corneal epithelial cells release cytokines
and chemokines
. Immune cells are released from limbal blood vessels
. The infiltrate
is an aggregation of neutrophils
, lymphocytes
and macrophages
as part of the inflammatory response.
Sterile corneal infiltrative events are associated with ...
have been previously categorised as ...
(CLPU) and ...
(CLARE).
Sterile corneal infiltrative events are associated with contact lens wear
have been previously categorised as contact lens peripheral ulcer
(CLPU) and contact lens acute red eye
(CLARE).
What should be considered when differentially diagnosing sterile infiltrates and microbial keratitis?
- Consider px history & presentation
- Consider treating all infiltrative events as infectious in nature
What are the differences between sterile infiltrate and microbial keratitis in terms of aetiology, prevalence, pain, vision, photophobia, tearing and discharge?
Sterile infiltrate:
* Inflammatory
* More common (22x more common than MK)
* Pain: mild to moderate
* Vision: usually unaffected
* Mild photophobia
* Mild tearing
* Mild discharge (not always)
Microbial Keratitis
* Infective
* Relatively rare
* Increasing & severe pain
* Usually reduced vision
* Moderate/ Severe photophobia
* Intense tearing
* Significant discharge
What are the differences between sterile infiltrate and microbial keratitis in terms of numbers, location, shape, size, staining, & staining association?
Sterile infiltrate:
* Sometimes multiple infiltrates
* Peripheral or mid-peripheral
* More likely circular
* < 2.0mm
* Staining possible
* Staining smaller in size than infiltrate
Microbial Keratitis
* Single lesion ulcer, satellite lesions possible
* Anywhere, including central
* More likely irregular shape
* > 1.0mm
* Staining present
* Staining matches ulcer size
What are the differences between sterile infiltrate and microbial keratitis in terms of depth,conojunctival response, lid oedema, anterior chamber reaction, and discontinuing CL wear?
Sterile infiltrate:
* Anterior stroma only
* Conjunctival hyperaemia: sectorial, mild to moderate
* No lid oedema
* None or minimal anterior chamber reaction
* Discontinuing CL wear helps resolve infiltrates
Microbial keratitis:
* Anterior to mid stromal, raised edges
* Conjunctival hyperaemia: generalised, moderate to severe (meaty)
* Lid oedema usually present
* Moderate anterior chamber reaction, occasional hypopyon
* Discontinuing CL wear usually worsens microbial keratitis
What is the abbreviation for differentiating between sterile infiltrate and microbial keratitis?
PEDALS = Pain, Epithelial defect, Discharge, Anterior chamber, Location & Size
What are the differences between sterile infiltrate and microbial keratitis in terms of appearance of fluorescein staining?
Sterile infiltrate
* White/ faint grey colour, distinct margins, circular/ oval
* Stains patchy, incomplete staining pattern
Microbial keratitis
* Grey/green-yellow colour, hazy, ill-defined margins of any shape
* Pools, fills area of tissue excavation
What is the name of the grading scale that help differentiate between sterile infiltrate and microbial keratitis? What does it account for and what do the scorings represent?
Modified Aasuri Grading Scale, accounting for multiple infiltrates.
< 8 = non-severe keratitis
> 8 = severe keratitis
> 12 = microbial keratitis
Sterile infiltrates can result from the ...
response from ...
. These often present as ...
infiltrates, which may have overlying ...
. There is often a ...
of 1-2mm between the infiltrate and the ...
. There may be confluent ...
with delayed ...
in to the epithelium and superficial ...
. Lesions appeaer in areas of direct contact between the ...
and ...
(...
o’clock and ...
o’clock)
The risk factors assocaited with this type of sterile infiltrate are: ...
, current or recent ...
and previous episodes of ...
Sterile infiltrates can result from the toxic or hypersensitivity
response from Staphylococcal bacteria exotoxins
. These often present as peripheral subepithelial marginal
infiltrates, which may have overlying epithelial breakdown
. There is often a clear intervening zone
of 1-2mm between the infiltrate and the limbus
. There may be confluent superficial punctate keratitis
with delayed fluorescein staining
in to the epithelium and superficial stroma
. Lesions appeaer in areas of direct contact between the peripheral cornea
and eyelid margin
(2-10
o’clock and 4-8
o’clock)
The risk factors assocaited with this type of sterile infiltrate are: anterior blepharitis (staphylococcus)
, current or recent upper respiratory tract infection
and previous episodes of marginal infiltrates
What are the two associations with sterile infiltrates?
Blepharitis and contact lens wear (CLPU, CLARE, CLAIK)
CLPU stands for ...
. These have characteristic small, ...
, ...
...
sterile infiltrates. Other symptoms include ...
and ...
redness, ...
sensation and ...
pain. There are up to ...
% CLPU px that are asymptomatic.
CLPU stands for contact lens associated peripheral ulcer
. These have characteristic small, single
, circular
focal
sterile infiltrates. Other symptoms include limbal
and bulbar
redness, foreign body
sensation and severe to moderate
pain. There are up to 50
% CLPU px that are asymptomatic.
CLARE stands for ...
. This is characterised by the moderate to severe ...
of the conjunctiva. This also associates with small, ...
, more ...
, focal, sterile infiltrates. Other symptoms include ...
pain, ...
and ...
soon after waking.
CLARE stands for contact lens associated red eye
. This is characterised by the moderate to severe circumferential redness
of the conjunctiva. This also associates with small, multiple
, more diffused
, focal, sterile infiltrates. Other symptoms include moderate
pain, tearing
and photophobia
soon after waking.
CLAIK stands for ...
. This is associated with ...
infiltration, with or without ...
involvment, ...
of the cornea. These sterile infiltrates are ...
and can present in ...
. Other symptoms include mild to moderate ...
, ...
and occasional ...
.
CLAIK stands for contact lens associated infiltrative keratitis
. This is associated with anterior stromal
infiltration, with or without epithelial
involvment, mid periphery to periphery
of the cornea. These sterile infiltrates are small
and can present in multiples
. Other symptoms include mild to moderate irritation
, redness
and occasional discharge
.
Risk factors for sterile infiltrates associated with contact lens wear:
* ...
- highest risk between ...
yo
* ...
> ...
* High ...
>...
* Higher ...
* Current or recent ...
(Haemophilus influenzae)
* ...
* ...
(Staphylococcus)
* Previous episode of ...
event (4-6x increased risk)
* Use of ...
contact lenses - ...
* ...
of contact lens case
* ...
purchasing of contact lenses
* ...
wear of contact lenses
* ...
contact lens material (2x increased risk)
* ...
contact lens disinfection system
* ...
to contact lenses or lens cases
Risk factors for sterile infiltrates associated with contact lens wear:
* Age
- highest risk between 5-29
yo
* Males
> Females
* High refractive error
>5D
* Higher socio-economic status
* Current or recent upper respiratory tract infection
(Haemophilus influenzae)
* Smoking
* Anterior blepharitis
(Staphylococcus)
* Previous episode of corneal infiltrative
event (4-6x increased risk)
* Use of reusable
contact lenses - monthly or fortnightly
* Age
of contact lens case
* Online
purchasing of contact lenses
* Overnight
wear of contact lenses
* Silicon hydrogel
contact lens material (2x increased risk)
* Multipurpose
contact lens disinfection system
* Water exposure
to contact lenses or lens cases
What are the 6 differential diagnosis of sterile marginal infiltrates?
- Contact lens associated microbial keratitis
- Rosacea keratitis
- Peripheral keratitis associated with rheumatoid arthritis or another systemic collagen vascular disease
- Mooren’s ulcer
- Phlytenular keratoconjunctivitis
- Terrien’s marginal degeneration
What are the treatments for Staphylococcal marginal infiltrates associated with blepharitis? (7)
Lids
* Lid hygiene - warm compresses, lid cleansers, lid debridement
* Antibiotic ointment to reduce bacterial load on lids
* Steroid ointment to reduce lid inflammation
Cornea
* Steroid drops to treat infiltrate -> FML 0.1% loading dose (every 15 mins for first hour, then QID until resolved, slowly taper equivalent to treatment period)
* Antibiotics -> chloromycetin 0.5 drops (chlorsig) QID no taper
* If no improvement -> oral doxycycline
* Emphasise the condition is chronic and requires ongoing compliance to adequately manage symptoms
What are the treatments for CL associated marginal infiltrates (CLPU, CLARE, CLAIK)?
”* Cease CL wear -> Signs/ symptoms usually improve rapidly after
* Prescribe antibiotic against staphylococcus and pseudomonas
-> Mild = Tobramycin 0.3% drops (Tobrex)
-> Severe = Fluoroquinolone (ciprofloxacin 0.3% (Ciloxan) or ofloxacin 0.3% (Ofloxacin)
* initially every 15mins then QID, no tapering
* Monitor px closely over first 12-24 hours
* Continue antibiotic for 2 days following epithelium healing, then stop and no taper
* Once epithelium has healed, prescribe steroid -> Fluorometholone acetate 0.01% drops (Flarex) QID until inflammation has resolved
* Slowly taper steroid over equivalent of treatment period
What are the long term management for CL associated marginal infiltrates (CLPU, CLARE, CLAIK)?
Long term management - intervene on modifiable risk factors
* Eyelid hygiene maintenance
* Recommend stop smoking
* Avoid or minimise extended CL wear
* Consider hydrogen peroxide cleaning regime
* Consider swapping from SiHy to hydrogel lenses
* Increase frequency of CL and case replacement
* Consider stopping from reusable CLs to daily replacement lenses
What is the prognosis of CL associated marginal infiltrates?
(2 points)
- Scarring is rare, but it is does, it will appear as a Bull’s eye scar
- Recurrence is likely
There are 4 microbe classes that can cause microbial keratitis: ...
, ...
, ...
and ...
. All MK infections begin as ...
and situates ....
. MK may result in corneal ....
and possible ...
. MK keratitis rarely occurs in the absence of ...
factors. There severity of MK is based on ...
, ...
, and ...
. MK affects both ...
and ...
quality of life. Even when visual recoery was complete, px demonstrated ...
. At RVEEH, there are ...
cases each year.
There are 4 microbe classes that can cause microbial keratitis: bacteria
, virus
, fungus
and parasites
. All MK infections begin as small infiltrates
and situates peripherally
. MK may result in corneal perforation
and possible endophthalmitis
. MK keratitis rarely occurs in the absence of predisposing
factors. There severity of MK is based on infiltrate sizes
, location
, and anterior chamber reaction
. MK affects both vision related
and psychological
quality of life. Even when visual recoery was complete, px demonstrated a lower quality of life score following MK
. At RVEEH, there are 100
cases each year.
What are the 4 risk factors of microbial keratitis?
- Contact lens wear
*Trauma - Ocular surface disease
- Post corneal surgery
Diagnosis requires careful ...
and assessment of ... and ...
. ...
is the gold standard to determine the microbe involved and is recommended in ...
. Treatment must be initiated ...
in suspected MK cases. A delay of even ...
can increase the likelihood of ...
and ... of the disease
.
Diagnosis requires careful history
and assessment of signs and symptoms
. Corneal culture
is the gold standard to determine the microbe involved and is recommended in all cases of MK
. Treatment must be initiated urgently
in suspected MK cases. A delay of even 12 hours
can increase the likelihood of vision loss
and duration of the disease
.