Diffuse lamellar keratitis: isolation of endotoxin and demonstration of the inflammatory potential in a rabbit laser in situ keratomileusis model.
OBJECTIVE
To systematically examine sources of endotoxin contamination in eye centers as a potential cause of diffuse lamellar keratitis (DLK) and to demonstrate the inflammatory potential of endotoxin in a rabbit model of laser in situ keratomileusis (LASIK) surgery.


METHODS
University of Calgary, Calgary, Alberta, Canada.


METHODS
In this prospective study, all water sources that routinely come in contact with LASIK instruments, including sterilizer reservoirs, eyedrops, microkeratome blades, and cleaning solutions, were examined for endotoxins at 5 eye centers. Bacterial cultures were performed on water samples from 5 sterilizer reservoirs. A LASIK flap was created in 8 rabbit eyes using an Automated Corneal Shaper microkeratome (Bausch & Lomb). The flaps were reflected, and a dose of endotoxin at various concentrations was placed on the interface. After 1 minute, the flap was irrigated and repositioned. The rabbit eyes were examined daily with a slitlamp biomicroscope for 3 days for the development of DLK, which was classified on a scale from grade 1 to 4 (mild to severe). The rabbits were killed at the conclusion of the study, and the interfaces were stained to rule out infectious etiologies.


RESULTS
Endotoxin was detected in significant concentrations in tap water, filtered and distilled water, instrument washbasins, and sterilizer reservoirs at all 5 centers. The cultures of the water samples taken from the sterilizer reservoirs ranged from no growth to the presence of >100 colony-forming units of Flavobacterium and Pseudomonas aeruginosa. Endotoxins caused DLK-like interface inflammation in all eyes tested. Examination of stained scrapings showed no microorganisms in the interface of the rabbit eyes.


CONCLUSIONS
Endotoxin contamination was detected in water sources that routinely come in contact with LASIK instruments. Endotoxins were capable of inducing interface inflammation in a rabbit model and may therefore be a significant factor in epidemic DLK.
Peters
N T
NT
Gimbel Eye Centre, Calgary, Alberta, Canada. lasik@nationwidevision.com
Iskander
N G
NG
Anderson Penno
E E
EE
Woods
D E
DE
Moore
R A
RA
Gimbel
H V
HV
D000818:Animals; D003319:Corneal Stroma / Q000187:drug effects* / Q000473:pathology; D004731:Endotoxins / Q000302:isolation & purification* / Q000633:toxicity; D004866:Equipment Contamination; D005417:Flavobacterium / Q000302:isolation & purification*; D006801:Humans; D007634:Keratitis / Q000139:chemically induced* / Q000473:pathology; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D023421:Models, Animal; D011446:Prospective Studies; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification*; D011817:Rabbits; D013524:Surgical Flaps; D014871:Water Microbiology
D004731:Endotoxins