March 1994
Volume 35, Issue 3
Free
Articles  |   March 1994
Stromal acidosis modulates corneal swelling.
Author Affiliations
  • N A McNamara
    Morton D. Sarver Laboratory for Cornea and Contact Lens Research, School of Optometry, University of California, Berkeley 94720.
  • K A Polse
    Morton D. Sarver Laboratory for Cornea and Contact Lens Research, School of Optometry, University of California, Berkeley 94720.
  • J A Bonanno
    Morton D. Sarver Laboratory for Cornea and Contact Lens Research, School of Optometry, University of California, Berkeley 94720.
Investigative Ophthalmology & Visual Science March 1994, Vol.35, 846-850. doi:
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      N A McNamara, K A Polse, J A Bonanno; Stromal acidosis modulates corneal swelling.. Invest. Ophthalmol. Vis. Sci. 1994;35(3):846-850.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

PURPOSE: Studies have shown that stromal acidosis reduces the rate of corneal thickness recovery after induced edema, providing the first human in vivo evidence that corneal pH can influence corneal hydration control. This finding raises the question of the possible effect that pH may have on induced corneal swelling. To explore this question, the corneal swelling response to hypoxia was measured while stromal pH was controlled. METHODS: Corneal edema and stromal acidosis was induced in ten subjects by passing a mixture of nitrogen and carbon dioxide gas across the eyes through tight-fitting goggles. One eye of each subject received 100% N2, whereas the contralateral eye received a mixture of 95% N2 and 5% CO2. Exposures of 95% N2 + 5% CO2 lower pH on average to 7.16 versus 7.34 for 100% N2 alone. Before and after 2.5 hours of gas exposure, central corneal thickness (CCT) was measured. RESULTS: Eyes exposed to the lower pH environment (eg, N2 + CO2) developed less change in CCT compared to the eyes receiving N2 alone. Overall increase in CCT was 29.9 +/- 5.3 microns for eyes exposed to the 95% N2 + 5% CO2 gas mixture, versus 37.1 +/- 4.8 microns for 100% N2 eyes (P < 0.0001). CONCLUSIONS: The corneal swelling response to hypoxia can be reduced by lowering stromal pH. Because changes in corneal pH alone have not been found to alter steady-state CCT, it is proposed that pH exerts its effect only under non-steady-state conditions (ie, corneal swelling and deswelling). This suggests that acidosis may produce changes in the rate of lactate metabolism or alter endothelial hydraulic conductivity.

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