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Oxygen: how well is the closed eye being served?
K E Galvin1, B A Fink, R M Hill
1Ohio State University, College of Optometry, Columbus, USA.
Optometry (St. Louis, Mo.)
|September 7, 2000
Summary
Contact lens wear significantly impacts corneal oxygen levels, especially with closed eyes. This study models these oxygen uptake rates, revealing a persistent "hypoxic gap" between closed and open eye conditions even with high Dk/t lenses.
Area of Science:
- Ophthalmology
- Corneal Physiology
- Contact Lens Science
Background:
- The naturally closed eye environment stresses corneal oxygen-dependent processes.
- Contact lens wear further intensifies these oxygen stresses on the cornea.
Purpose of the Study:
- To quantify human corneal responses to various Dk/t levels under closed-eye conditions.
- To define the "hypoxic gap" between closed-eye and open-eye corneal responses.
- To develop predictive models for corneal oxygen response functions.
Main Methods:
- Measured oxygen uptake rates polarographically in open eyes.
- Assessed corneal responses after closed- and open-eye wear of six rigid contact lenses with varying transmissibilities (Dk/t).
Main Results:
- Corneal responses under closed-eye conditions were modeled using natural log equations (R2 > 0.99).
- A significant separation (p < 0.05) between closed- and open-eye responses was observed at Dk/t levels above 12.8 x 10(-9).
- Even at the highest Dk/t (91 x 10(-9)), closed-eye responses remained higher than open-eye responses.
Conclusions:
- Corneal oxygen uptake under closed-eye conditions is significantly different from open-eye conditions.
- A predictive model for Dk/t effectiveness in meeting corneal oxygen needs was developed.
- The "hypoxic gap" appears to stabilize at higher Dk/t levels, indicating persistent oxygen stress during closed-eye wear.