Microbiology & Disinfection Flashcards
Major predisposing factors for MK
CL wear
Trauma
Ocular surface disease
Minor predisposing factors for MK
Non-compliance
Age (university age)
Male sex
Smoking
MK risk factors from Stapelton et al
Over night wear Poor case hygiene Smoking Internet CL purchase <6mos wear Higher socioeconomic class
MK risk factors from Dart et al
Daily disposables (SpecSavers, abuse of lenses) Occasional overnight wear Overnight wear Days worn/wk Hypermetropia Lack of hand washing Younger age Male gender
EW SiHy and MK
No reduction in incidence
But lower morbidity, and swifter recovery (more O2)
Ocular defence mechanisms
Lids - blinking, flushing effect
Mucin - barrier
Epithelium - intact
Tears - antibacterial proteins (lysozyme)
Occurrence of Staph on the lids
90%
Occurrence of Corynebacterium on lids
20%
Occurrence of Propionibacterium on lids
80%
What bugs cause MK in non-lens wearer?
G+
S aureus (50%), S pneumoniae
Stretococci
What bugs cause MK in CL wearer?
G-
P aeruginosa (70%)
Haemophilus influenzae
Serratia marcescens
What bugs can invade an intact cornea?
Corynebacterium diptheriae
H influenzae
N gonorrhoea
What is the increased risk of MK in Px’s who don’t wash their hands prior to lens handling?
1.49x
What is the difference in the bacterial counts of a lens that has been handled vs a lens that has been worn?
Handled = 100% contaminated Worn = 43% contaminated
Approx what percentage of people wash their hands before handling lenses?
About 56% in the morning, only 51% at night
