A single-lens polarographic measurement of oxygen permeability (Dk) for hypertransmissible soft contact lenses

Chhabra, Mahendra; Prausnitz, John M.; Radke, Clayton J.

doi:10.1016/j.biomaterials.2007.06.024

Cited by 21 publications

(30 citation statements)

References 51 publications

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“…Partition coefficients values are those from Table II. Also shown in Table III is the tortuosity (τ) of each hydrogel established from the relation: 40 where D 0 is the molecular self‐diffusion coefficient of aqueous sodium chloride (2.089 × 10 −5 at 35°C41). The tortuosities decrease with increasing water content, as expected.…”

Section: Resultsmentioning

confidence: 99%

Permeability and partition coefficient of aqueous sodium chloride in soft contact lenses

Guan

Jiménez

Walowski

et al. 2011

J of Applied Polymer Sci

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Transport of physiologic saline through soft contact lenses is important to on-eye behavior. Using a specially designed Stokes-diaphragm cell, we measure aqueous NaCl permeabilities through commercial soft contact lenses at 35 C. The permeabilities increase exponentially with the water content of the lenses spanning a range from 10 À7 to 10 À5 cm 2 /s. Equilibrium partition coefficients are obtained by the backextraction of lenses initially immersed in 1M aqueous NaCl. Partition coefficients also increase with lens water content but over a smaller range, from 0.1 to 0.7. Because the partition coefficient values are smaller than the water content of the lenses, ideal theory is not followed. Donnan exclusion, bound water, and excluded volume are proposed explanations. The diffusion coefficients of aqueous NaCl through soft contact lenses increase with increasing lens water content following free-volume theory. Aqueous NaCl diffusivities in the lower water-content lenses are smaller than the diffusion coefficient of NaCl in water by factors up to 100 indicating very tortuous diffusion paths.

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Section: Resultsmentioning

confidence: 99%

Permeability and partition coefficient of aqueous sodium chloride in soft contact lenses

Guan

Jiménez

Walowski

et al. 2011

J of Applied Polymer Sci

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“…Using a new approach, a recent study showed that these Dk values were consistent except for Lotrafilcon A (140), which gave a significantly different value (180). 7 All lenses had back surface radii of ~8.6 mm, diameter of 13.5 mm, and −0.50 D power to achieve uniform thickness. An ET-1 thickness gauge (Rehder Development Co., Castro Valley, CA) was used to verify lens thickness.…”

Section: Methodsmentioning

confidence: 99%

“…2–4 These factors were the major impetus for the contact lens industry to develop highly oxygen permeable materials and resulted in the introduction of silicone hydrogel (SiH) lenses several years ago. Although there have been a number of studies examining clinical complications of SiH lens use relative to conventional hydrogels, and measuring the oxygen transmissibility of SiH lenses, 5–7 there has been very little measurement data gathered for the “on eye” oxygen delivery performance of SiH lenses.…”

mentioning

confidence: 99%

Tear Oxygen Under Hydrogel and Silicone Hydrogel Contact Lenses in Humans

Bonanno¹,

Clark²,

Pruitt³

et al. 2009

Optometry and Vision Science

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Purpose To determine the tear oxygen tension under a variety of conventional and silicone hydrogel contact lenses in human subjects. Methods Three hydrogel and five silicone hydrogel lenses (Dk/t = 17 to 329) were coated on the back surface with an oxygen sensitive, bovine serum albumin-Pd meso-tetra (4-carboxyphenyl) porphine complex (BSA-porphine). Each lens type was placed on the right eye of 15 non-contact lens wearers to obtain a steady-state open eye tear oxygen tension using oxygen sensitive phosphorescence decay of BSA-porphine. A closed-eye oxygen tension estimate was obtained by measuring the change in tear oxygen tension after 5 min of eye closure. In separate experiments, a goggle was placed over the lens wearing eye and a gas mixture (PO2 = 51 torr) flowed over the lens to simulate anterior lens oxygen tension during eye closure. Results Mean open eye oxygen tension ranged from 58 to 133 torr. Closed eye estimates ranged from 11 to 42 torr. Oxygen tension under the goggle ranged from 8 to 48 torr and was higher than the closed eye estimate for six out of the eight lenses, suggesting that the average closed eye anterior lens surface oxygen tension is <51 torr. For Dk/t >30, the measured tear oxygen tension is significantly lower than that predicted from previous studies. Conclusions The phosphorescence decay methodology is capable of directly measuring the in vivo post lens PO2 of high Dk/t lenses without disturbing the contact lens or cornea. Our data indicate that increasing Dk/t up to and beyond 140 continues to yield increased flux into the central cornea.

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“…Provided the flow evaporimeter obeys eq 3 with an evaporative resistance of the TFLL independent of flow velocity, measurement of ΔC/J E as a function of air velocity to the negative β power for differing relative humidities yields a straight line independent of relative humidity. 71 The slope of that line depends only on the instrument, independent of the human subject. The intercept specifies the resistance of the TFLL which in the dissolution/ diffusion picture of Figure 1 is given by…”

Section: Evaporimeter Designmentioning

confidence: 99%

Flow Evaporimeter To Assess Evaporative Resistance of Human Tear-Film Lipid Layer

Peng

Cerretani

et al. 2014

Ind. Eng. Chem. Res.

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A novel in vivo flow evaporimeter is developed to measure human tear-evaporation rates. The flow evaporimeter relies on a well-defined flow field to the eye with known and adjustable flow rates and relative humidities, and quantitatively reproduces evaporation rates for pure water. Mass-transfer analysis of the evaporimeter data elucidates, for the first time, the resistance of the human tear-film lipid layer (TFLL) toward minimizing tear loss to the environment. A pilot study on human subjects validates the feasibility of the flow evaporimeter to obtain the tear-film evaporation rates in vivo. Resistance of the TFLL against tear evaporation is found subject specific. Our flow evaporimeter offers an accurate, safe, and convenient diagnostic tool for clinical evaluation of dry-eye-related maladies.

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A single-lens polarographic measurement of oxygen permeability (Dk) for hypertransmissible soft contact lenses

Cited by 21 publications

References 51 publications

Permeability and partition coefficient of aqueous sodium chloride in soft contact lenses

Permeability and partition coefficient of aqueous sodium chloride in soft contact lenses

Tear Oxygen Under Hydrogel and Silicone Hydrogel Contact Lenses in Humans

Flow Evaporimeter To Assess Evaporative Resistance of Human Tear-Film Lipid Layer

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