Tear oxygen under hydrogel and silicone hydrogel contact lenses in humans.
OBJECTIVE
To determine the tear oxygen tension under a variety of conventional and silicone hydrogel contact lenses in human subjects.


METHODS
Three hydrogel and five silicone hydrogel lenses (Dk/t = 17 to 329) were coated on the back surface with an oxygen sensitive, bovine serum albumin-Pd meso-tetra (4-carboxyphenyl) porphine complex (BSA-porphine). Each lens type was placed on the right eye of 15 non-contact lens wearers to obtain a steady-state open eye tear oxygen tension using oxygen sensitive phosphorescence decay of BSA-porphine. A closed-eye oxygen tension estimate was obtained by measuring the change in tear oxygen tension after 5 min of eye closure. In separate experiments, a goggle was placed over the lens wearing eye and a gas mixture (PO2 = 51 torr) flowed over the lens to simulate anterior lens oxygen tension during eye closure.


RESULTS
Mean open eye oxygen tension ranged from 58 to 133 torr. Closed eye estimates ranged from 11 to 42 torr. Oxygen tension under the goggle ranged from 8 to 48 torr and was higher than the closed eye estimate for six out of the eight lenses, suggesting that the average closed eye anterior lens surface oxygen tension is <51 torr. For Dk/t >30, the measured tear oxygen tension is significantly lower than that predicted from previous studies.


CONCLUSIONS
The phosphorescence decay methodology is capable of directly measuring the in vivo post lens PO2 of high Dk/t lenses without disturbing the contact lens or cornea. Our data indicate that increasing Dk/t up to and beyond 140 continues to yield increased flux into the central cornea.
Bonanno
Joseph A
JA
School of Optometry, Indiana University, Bloomington, Indiana 47405, USA. jbonanno@indiana.edu
Clark
Christopher
C
Pruitt
John
J
Alvord
Larry
L
D000328:Adult; D003263:Contact Lenses, Hydrophilic; D003315:Cornea / Q000378:metabolism; D005260:Female; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D010313:Partial Pressure; D012828:Silicones; D013666:Tears / Q000378:metabolism*; D055815:Young Adult
D012828:Silicones; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D010100:Oxygen