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Corneal oxygen consumption and concentration levels during corneal cross-linking with and without supplementary oxygen

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First Author: T.G.Seiler SWITZERLAND

Co Author(s):    M. Komninou   K. Schuerch   B. Früh              

Abstract Details

Purpose:

To measure the oxygen consumption and concentration during corneal cross-linking (CXL) in different depths and compare different protocols with and without supplementary oxygen.

Setting:

Laboratory comparative study at the Department of Ophthalmology, University of Bern, Switzerland

Methods:

In de-epithelialized porcine eyes, a femtosecond-laser generated channel was used to place a fiber-probe in corneal depths of 100, 200 and 300 microns to measure the local oxygen concentration. After a 10 minutes imbibition of 0.1% riboflavin the corneas were irradiated at 3, 9, 18 and 30 mW/cm2 while the oxygen concentration was continuously measured. To assess the benefit of supplementary oxygen, all experiments were performed under atmospheric (21% O2) as well as under hyperoxygenic (more than 95% O2) conditions.

Results:

The equilibrium oxygen concentration under atmospheric oxygen conditions at 3mW/cm2 was 5% in 100 microns decreasing to 3% in 200 microns and 0% at 300 microns. With 9, 18 and 30 mW/cm2 no oxygen was available in 100 microns or deeper. Using a hyperoxygenic environment the oxygen concentration was 50% using 3mW/cm2 in 100 microns decreasing to 46% in 200 microns and 39% in 300 microns. At 9 mW/cm2 the concentrations were 5%, 3% and 1% in 100, 200 and 300 microns, respectively. Using 18 and 30 mW/cm2 all oxygen was depleted during CXL and no equilibrium was established, however, the time until all oxygen was consumed was longer in the 18mW/cm2 than in the 30mW/cm2.

Conclusions:

Supplementary environmental oxygen increases the stromal oxygen-availability during CXL. In particular at higher irradiances with increased oxygen consumption, supplementary oxygen is beneficial and eliminates the bottleneck of oxygen and, therefore, allows a more efficient cross-linking.

Financial Disclosure:

... receives non-monetary benefits from a company producing, developing or supplying the product or procedure presented