Hydrogel contact lens dehydration and oxygen transmissibility
Efron, N.; Morgan, P.B.
Clao Journal Official Publication of the Contact Lens Association of Ophthalmologists Inc 25(3): 148-151
1999
ISSN/ISBN: 0733-8902 PMID: 10444050 Document Number: 502780
Purpose: Oxygen transmissibility is a key determinant of the physiological response of the cornea to contact lens wear. Because transmissibility is related to hydrogel water content, we conducted a study to determine the change in water content during lens wear and to quantity the impact any such change would have on transmissibility. Methods: In a double masked clinical investigation, two subjects each wore 17 different pairs of contact lenses. Water content was measured before lens wear at 35degreeC and immediately after 4 hours of contact lens wear. Contact lens oxygen transmissibilities were calculated on each occasion. Results: The absolute changes in water content for the 17 lenses varied from +0.5% to -5.3%. For some lenses, this change in water content altered the lens oxygen transmissibilities to a clinically significant degree. The changes in water content and oxygen transmissibilities were greatest with FDA Group IV lenses. Conclusions: Dehydration during contact lens wear can alter the oxygen transmissibility of hydrogel lenses, and in some situations, this factor may be clinically significant.