Abstract/Details

Oxygen transport through soft contact lens and cornea: Lens characterization and metabolic modeling


2007 2007

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Abstract (summary)

The human cornea requires oxygen to sustain metabolic processes critical for its normal functioning. Any restriction to corneal oxygen supply from the external environment (e.g., by wearing a low oxygen-permeability contact lens) can lead to hypoxia, which may cause corneal edema (swelling), limbal hyperemia, neovascularization, and corneal acidosis. The need for adequate oxygen to the cornea is a major driving force for research and development of hypertransmissible soft contact lenses (SCLs).

Currently, there is no standard technique for measuring oxygen permeability (Dk) of hypertransmissible silicone-hydrogel SCLs. In this work, an electrochemistry-based polarographic apparatus was designed, built, and operated to measure oxygen permeability in hypertransmissible SCLs. Unlike conventional methods where a range of lens thickness is needed for determining oxygen permeabilities of SCLs, this apparatus requires only a single lens thickness. The single-lens permeameter provides a reliable, efficient, and economic tool for measuring oxygen permeabilities of commercial hypertransmissible SCLs.

The single-lens permeameter measures not only the product Dk, but, following modification, it measures separately diffusivity, D, and solubility, k, of oxygen in hypertransmissible SCLs. These properties are critical for designing better lens materials that ensure sufficient oxygen supply to the cornea.

Metabolism of oxygen in the cornea is influenced by contact-lens-induced hypoxia, diseases such as diabetes, surgery, and drug treatment, Thus, estimation of the in-vivo corneal oxygen consumption rate is essential for gauging adequate oxygen supply to the cornea. Therefore, we have developed an unsteady-state reactive-diffusion model for the cornea-contact-lens system to determine in-vivo human corneal oxygen-consumption rate.

Finally, a metabolic model was developed to determine the relation between contact-lens oxygen transmissibility (Dk/L) and corneal oxygen deficiency. A new parameter "Oxygen Deficiency Factor" (ODF) is defined to quantify oxygen deficiency in local regions of the cornea. We use this concept to determine the minimum required contact-lens oxygen transmissibility, Dk/L = 150 Barrer/cm, to avoid hypoxia-induced corneal physiologic complications.

Indexing (details)


Subject
Biomedical research;
Chemical engineering;
Materials science
Classification
0541: Biomedical research
0542: Chemical engineering
0794: Materials science
Identifier / keyword
Applied sciences; Contact lens; Cornea; Metabolism; Oxygen; Oxygen transport; Polarographic; Silicone hydrogels
Title
Oxygen transport through soft contact lens and cornea: Lens characterization and metabolic modeling
Author
Chhabra, Mahendra
Number of pages
212
Publication year
2007
Degree date
2007
School code
0028
Source
DAI-B 69/03, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780549528074
Advisor
Radke, Clayton J.; Prausnitz, John M.
University/institution
University of California, Berkeley
University location
United States -- California
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3306100
ProQuest document ID
304901209
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304901209
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