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Stromal acidosis modulates corneal swelling
N A McNamara1, K A Polse, J A Bonanno
1Morton D. Sarver Laboratory for Cornea and Contact Lens Research, School of Optometry, University of California, Berkeley 94720.
Investigative Ophthalmology & Visual Science
|March 1, 1994
Summary
Lowering stromal pH reduces corneal swelling during hypoxia. This suggests that corneal pH influences hydration control, particularly during swelling and deswelling, potentially by affecting lactate metabolism or endothelial function.
Area of Science:
- Ophthalmology
- Corneal Physiology
- Acid-Base Balance
Background:
- Stromal acidosis is known to slow corneal thickness recovery after induced edema.
- This suggests corneal pH influences hydration control.
- The effect of pH on induced corneal swelling requires further investigation.
Purpose of the Study:
- To investigate the effect of stromal pH on corneal swelling response to hypoxia.
- To determine if controlling stromal pH impacts corneal hydration during hypoxic stress.
Main Methods:
- Hypoxic corneal edema and stromal acidosis were induced in ten subjects using nitrogen and carbon dioxide gas mixtures.
- One eye received 100% N2 (higher pH), while the contralateral eye received 95% N2 + 5% CO2 (lower pH).
- Central corneal thickness (CCT) was measured before and after 2.5 hours of gas exposure.
Main Results:
- Eyes exposed to lower pH (N2 + CO2) showed significantly less corneal swelling compared to eyes exposed to higher pH (N2 alone).
- The average increase in CCT was 29.9 ± 5.3 microns in the lower pH group versus 37.1 ± 4.8 microns in the higher pH group (P < 0.0001).
Conclusions:
- Lowering stromal pH reduces the corneal swelling response to hypoxia.
- The effect of pH on corneal swelling appears to occur under non-steady-state conditions, such as during swelling and deswelling.
- This suggests that acidosis may alter lactate metabolism or endothelial hydraulic conductivity, impacting corneal hydration.