The relation between contact lens oxygen transmissibility and binding of Pseudomonas aeruginosa to the cornea after overnight wear.
OBJECTIVE
To assess adverse effects of contact lens-induced hypoxia on the rabbit cornea in vivo and determine the relation between binding of Pseudomonas aeruginosa and oxygen transmissibility for rigid and hydrogel lenses.


METHODS
Six rigid lenses with Dk/Ltotal values between 0 and 97 x 10(-9) (cm/second) (ml O2/ml mmHg) and four hydrogel lenses (Dk/Ltotal 9, 20, 39, 51) were tested. All lenses had 14.0-mm diameters and a thickness (parallel) of 0.12 or 0.15 mm. Tear lactate dehydrogenase activity and tandem scanning confocal microscopy determinations were performed after the lens was worn for 24 hours. Binding of P. aeruginosa then was separately determined by the colony-forming unit method. Scanning electron microscopy was used to confirm in vivo tandem scanning confocal microscopy findings.


RESULTS
Lens oxygen transmissibility determines binding of P. aeruginosa to the cornea after the lens is worn for 24 hours; epithelial damage produced by lenses of lower Dk/Ltotal appears to be the dominant biologic factor for P. aeruginosa binding and not lens rigidity.


CONCLUSIONS
These results suggest that the risk of P. aeruginosa keratitis developing with overnight wear will be enhanced significantly for contact lenses with Dk/Ltotal values less than 50 x 10(-9) (cm/second) (ml O2/ml mmHg) (human equivalent oxygen percentage < or = 15%), and this risk will increase with further decreases in oxygen transmissibility. Because no hydrogel lenses approved by the Food and Drug Administration are available with oxygen transmission at this level, patients should be made aware of the increased risk of infectious keratitis associated with the overnight wear of current extended wear hydrogel lenses. Results of this study also demonstrate that quantitative clinical tandem scanning confocal microscopy imaging and tear lactate dehydrogenase activity measurements can provide prospective, noninvasive methods for assessing the ongoing interaction between contact lens and cornea in vivo.
Imayasu
M
M
Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas 75235-9057.
Petroll
W M
WM
Jester
J V
JV
Patel
S K
SK
Ohashi
J
J
Cavanagh
H D
HD
D000818:Animals; D001422:Bacterial Adhesion; D015169:Colony Count, Microbial; D003261:Contact Lenses; D003315:Cornea / Q000382:microbiology / Q000502:physiology* / Q000648:ultrastructure; D003320:Corneal Ulcer / Q000382:microbiology / Q000473:pathology; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D020366:Methylmethacrylate; D008768:Methylmethacrylates; D010100:Oxygen; D011092:Polyethylene Glycols; D011550:Pseudomonas aeruginosa / Q000502:physiology* / Q000648:ultrastructure; D011817:Rabbits; D013666:Tears / Q000201:enzymology
D008768:Methylmethacrylates; D020366:Methylmethacrylate; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols; D007770:L-Lactate Dehydrogenase; D010100:Oxygen