Keratitis Flashcards
What are some infectious cases of keratitis ?
- bacterial
- viral
- protozoal
- fungal
What are some non-infectious cases of keratitis?
- Inflammatory
- Exposure
- Latrogenic
What is the structure of the cornea?
5 layers starting from anterior -Epithelium -Bowmans membrane -Stroma- bulk POSTERIOR surface - decements membrane -endothelium
What does the term keratitis mean?
inflammation of the cornea
What does rose bengal dye do ?
stains damaged and dead cells
What can you not see with severe case of dry eye ?
no/poor quality reflections of the surface of the cornea
What is microbial keratitis ?
-Encompasses bacteria, viruses. fungi and protozoa
for e.g keratitis caused by acanthoemeba
What are the risk factors of developing microbial keratitis ?
- Trauma- breaches through natural anatomical surface of the defence of the ocular surface and creates a portal through which the micro-organsim enters the cornea- true if its in the nature
- CL wearers - major- especially who wears the CL overnight
- surgery - penetrating ocular surgery
- ocular surface disease- e.g people who have dry eyes, lid margin disease, blepharitis.
- immunosuppression - e.g people taking corticosteroids for a disorder
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all the diseases are sight threatening ophthalmic emergencies - anything compromises corneal integrity is sight threatening.
What is bacterial keratitis ?
- the most common cause of microbial keratitis - 60-90% of cases
What are the variety of bacterial pathogens that cause bacterial keratitis ?
- Pseudomonas sp. (Gram -ve)
- Staphylococcus sp. (Gram +ve)
- Streptococcus sp. (Gram +ve)
- other Gram -ve organisms
In non CL wearers, what is the infection (bacterial keratitis) most likely caused by ?
- gram +ve organism e.g -Staphylococcus species and -Streptococcus species .
In CL wearers, what is the infection (bacterial keratitis) most likely caused by ?
- Gram -ve bacteria is most commonly e.g -Pseudomonas sp. (very serious and sight threatening emergency )
What are risk factors bacterial keratitis in CL wearers ?
-Incidence of contact lens -related microbial keratitis
- 2–4 per 10,000 wearers per year for daily soft lens wearers
- 20 per 10,000 for overnight soft lens wearers
- more Overnight CL wearers are at a risk
- Poor lens hygiene major risk factor- people who wear monthly lenses, dont change solution each night and gets infected etc - not good care
What are the risk factors in - non-contact lens wearers in bacterial keratitis ?
- Immunosupression- e.g people taking corticosteroids
- Ocular surface disease- people who have dry eyes, lid margin disease, blepharitis.
- Trauma
What are the signs on bacterial keratitis ?
- infiltrate - exavaction of epithelium- got localised epithelial damage , extending. deeper into the cornea - anterior stroma - lesion - the cloudy/fluffy white appearance - usually central
- the deeper the lesion will resolve with a scar
- generally central
- large >1mm
- anterior to mid-stromal- full thickness epithelial loss
- Severe hyperamia
AC reaction
cells, flare to hypopyon
-Lid oedema
What is hypopnea ?
- illustrating there is significant anterior chamber inflammation
- see cells flare - inflammatory cells can deposit on the back surface of cornea
- collections of pus and dead bacteria will sit at the bottom of the cornea to form this hypopneon
- The flare is a breakdown at the blood aqueous barrier where protein floods into aqueous
What are the symptoms of the bacterial keratitis ?
- Unilateral
- Moderate to severe pain, rapid onset
- Reduced vision (location)
- Photophobia- sensitivity to light
What is the impact of vision in bacterial keratitis ?
impact on vision depends on location so for e.g if its peripheral the impact is minimal but off central it
What is the management for bacterial keratitis ?
-Immediately discontinue lens wear
-Refer to A&E (specialist unit)
.corneal scrape or biopsy- remove some of the infectious material with a view of determining the microorganism causing it
.Intensive anti-microbial treatment
.fluoroquinolone antibiotic e.g. levofloxacin
close monitoring - good antibiotics
- check antibiotic has particular sensitivity to the pathogen- so px need to be closely monitored.
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what is the corneal scrape process ?
- corneal biopsy
-done with a hypodermic needle - the important thing is to get deep into the lesion so not just scrape it - its a full scrape of the corneal ulcer/infiltrate
-then put the sample in a variety of different media
-could make assumption however need to check if more than 1 pathogen involved
-so uses a medium which supports fungal growth - such as as Saboraud agar (fungi)- most commonly used - some transport medium would allow them to look for viruses
-the technique used for this is PCR
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What are the different types of medium which support growth of pathogens in corneal scrape ?
A. Saboraud agar (fungi)
B. Chocolate agar (fastidious microorganisms, particularly Haemophilus and Neisseria )
C. Blood agar (Streptococci)
D. Thioglycolate broth (differentiates between aerobes and anaerobes)
E. Viral transport media
Why can px get antibiotic susceptibility ?
due to the increase in antimicrobial resistance antibiotic resistance- have these strains which develop resistance to the antibitotics
How do they test for antibiotic susceptibility ?
- looking for Zones of inhibition of bacterial growth may be present around the antibiotic disk. and the size of the zone of inhibition is dependent on the degree of sensitivity of the bacterium to the antibiotic
- this will give an idea of the the effectiveness of the particular antibiotic
What is the most common cause of microbial keratitis ?
bacterial keratitis
