May 2008
Volume 49, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2008
On-Eye Contact Lens Central vs. Temporal PO2 Measurements Compared to FEA Model of Corneal Oxygen Distribution Predicted Trends
Author Affiliations & Notes
  • C. F. Morgan
    RD&E, CIBA Vision Corp, Duluth, Georgia
  • G. Zhang
    Driftmier Engineering Center, University of Georgia, Athens, Georgia
  • L. Alvord
    RD&E, CIBA Vision Corp, Duluth, Georgia
  • J. A. Bonanno
    School of Optometry, Indiana University, Bloomington, Indiana
  • J. Hall
    RD&E, CIBA Vision Corp, Duluth, Georgia
  • Footnotes
    Commercial Relationships  C.F. Morgan, CIBA Vision Corporation, E; G. Zhang, CIBA Vision Corporation, C; L. Alvord, CIBA Vision Corporation, E; J.A. Bonanno, CIBA Vision Corporation, C; J. Hall, CIBA Vision Corporation, E.
  • Footnotes
    Support  None.
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 2018. doi:https://doi.org/
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      C. F. Morgan, G. Zhang, L. Alvord, J. A. Bonanno, J. Hall; On-Eye Contact Lens Central vs. Temporal PO2 Measurements Compared to FEA Model of Corneal Oxygen Distribution Predicted Trends. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2018. doi: https://doi.org/.

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

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Abstract

Purpose: : Recent modeling of corneal oxygen distribution based on Finite Element Analysis (FEA) predicts significant differences between PO2 beneath the central region of a contact lens compared to the periphery. The FEA model predicted differences are due to thickness profiles of the lens and the cornea. PO2 beneath two regions under two different lens geometries on the same eye are measured and compared to results predicted with the FEA model.

Methods: : The posterior surface of a -0.50D and a -6.00D ACUVUE®2 lens were coated with BSA-Pd-coproporphyrin. Phosphorescent decay rates measured from a 2.25 mm square spot in the open eye were used to calculate PO2 beneath the lenses. The spot was centered on the pupil for the central region and ~3.5 mm off-axis for the temporal region. A minimum of seven measurements were made in central and temporal regions. The FEA model employed a Monod constant of 4 torr with nominal maximum consumption coefficients (Qx) associated with the epithelium, stroma and endothelium of 25.9, 2.3, and 47.8 x10-5 mlO2 •sec-1 •cm-3. A single scaling factor was applied to these nominal values of Qx to fit the observed PO2.

Results: : The approximately constant thickness profile (~115 µm) of the -0.50D lens exhibited an approximately flat response in PO2 of between 62 and 72 Torr O2 in the central and temporal regions. The -6.00D lens thickness profile ranged from ~75 µm centrally to between 130 to 160 µm temporally. The PO2 response ranged from 82 to 90 Torr O2 centrally to 40 to 45 Torr O2 in the temporal region. The results from the FEA model were consistent with the observed PO2 from the -0.50D lens when Qx values ~70% of the nominal were used. The results from the FEA model were not consistent with the observed PO2 from the -6.00D lens when the same values of Qx were used.

Conclusions: : The approximately constant thickness profile (~115 µm) of the -0.50D lens exhibited an approximately flat response in PO2 of between 62 and 72 Torr O2 in the central and temporal regions. The -6.00D lens thickness profile ranged from ~75 µm centrally to between 130 to 160 µm temporally. The PO2 response ranged from 82 to 90 Torr O2 centrally to 40 to 45 Torr O2 in the temporal region. The results from the FEA model were consistent with the observed PO2 from the -0.50D lens when Qx values ~70% of the nominal were used. The results from the FEA model were not consistent with the observed PO2 from the -6.00D lens when the same values of Qx were used.

Keywords: contact lens • cornea: basic science • oxygen 
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