Irving Fatt

Oxygen tension under an oxygen-permeable contact lens.

&NA; The oxygen tension at the anterior corneal surface under an oxygen‐permeable contact lens is shown to be a function of the oxygen transmissibility and the thickness of the lens. The oxygen transmissibilities of several gel contact lenses and a silicone rubber lens are reported together with the procedure for making this measurement. Several of the lenses are shown to give, for an open eye, an oxygen tension at the corneal surface sufficient for maintenance of normal corneal thickness. None of the lenses tested will do this for the closed eye.

Effect of Fractional Wettability on Multiphase Flow Through Porous Media

The concept of fractional wettability is examined. Fractional water wettability of a reservoir rock is defined as the fraction of the internal surface area that is in contact with water. Capillary pressure and relative permeability of unconsolidated sand are shown to be functions of fractional wettability.

Flow conductivity of retina and its role in retinal adhesion

Abstract The flow conductivity of the rabbit retina has been measured and found to be 9·4 × 10 −9 cm 4 dyn −1 sec −1 at 37°. The measured density of the retina was found to be 1·0174 g/cm 3 . These properties of the retina are used to explain the adhesion of the retina to the underlying tissue. The major conclusion is that the retina cannot detach unless a tear or hole develops.

Oxygen tension distributions in the cornea: A re-examination

Abstract Previous calculations of the steady-state oxygen distribution in the in vivo cornea were made using assumed values for the needed parameters. Recent work has yielded experimental results on these quantities and we have used these to compute the oxygen tension distributions in the cornea for several conditions. The main result, which differs from the earlier calculations, is that there is an oxygen flux from the aqueous into the cornea in the open-eye steady-state condition. Oxygen tension profiles are also presented for the closed eye and for a corneal-contact lens system. Implications of the various profiles are discussed.

Oxygen Uptake from a Reservoir of Limited Volume by the Human Cornea in vivo

Oxygen flux across the anterior surface of the human cornea from a closed reservoir of air-saturated, physiological, isotonic saline was measured in vivo as a function of time. The rate of oxygen consumption calculated from this flux compares favorably with estimates given in the literalure, which were based on studies in which the microrespirometer technique of Warburg was used.

Flow of water in the sclera.

The flow conductivity of rabbit and human sclera as a function of hydration was measured. At normal hydration, 2·14 g water per g dry tissue, the flow conductivity at 37°C is 19 × 10−13 cm4 dynes−1 sec−1 for both species. If the aqueous humor is assumed to be hydraulically connected to the liquid in the suprachoroidal space, then there is an outflow via the sclera of 0·74 μl/min in rabbit and 0·53 μl/min in man. The fraction of the total aqueous humor drainage via the sclera is then 18% in the rabbit and 21% in man.

Dynamics of water transport in the corneal stroma.

The rate at which corneal stroma imbibes water is shown to be related to the flow conductivity and the slope of the imbibition pressure-hydration relationship. The equation that gives imbibition rate in terms of these static (time invariant) properties was obtained previously from a purely physicochemical treatment of water movement in a swelling membrane. A new experimental procedure to obtain imbibition pressure and flow conductivity as a function of hydration is described. The new procedure is more rapid and economical of tissue material needed than are previous methods. Flow conductivity appears to be related only to the physical properties of the stroma whereas imbibition pressure is related to both physical and chemical properties. The rate of water imbibition, therefore, is related to both the physical and chemical properties of the stroma.

Steady-state distribution of oxygen and carbon dioxide in the in vivo cornea: II. The open eye in nitrogen and the covered eye

The oxygen and carbon dioxide tension profiles in the in vivo cornea were calculated for the open eye in nitrogen and for the eye covered by a tight-fitting, oxygen-impermeable contact lens. The calculated profiles are somewhat dependent upon the relation of oxygen consumption rate to oxygen tension. A reasonable assumption for the oxygen consumption rate-oxygen tension relationship leads to the conclusion that for both the eye in nitrogen and the covered eye the endothelium has normal oxygen tension, the stroma has severely reduced oxygen tension, and the epithelium is almost anoxic.

Temperature measurements in the eye

Abstract An experimental and theoretical study shows that a metallic needle temperature probe reads in vivo eye temperatures significantly lower than the actual temperatures. In this study an epoxy-encased fine wire thermocouple probe was used to obtain in vivo ocular temperatures in rabbits. Radiometric surface temperatures were obtained over a range of wind velocities. The results obtained from a mathematical model were compared with the data obtained from the needle and fine wire temperature probes placed in the rabbit eye. The comparison suggests that intraocular temperature measurements are in error due to heat conduction losses from the probe and trauma to the eye. The errors are smaller for probes of fine wire than for needle-type probes. Results from the mathematical model can be used to predict intraocular temperatures in rabbits and humans for various air temperatures and wind velocities.

Theory of Oxygen Transport through Hemoglobin Solutions

A combination of equations describing diffusion, gas solubility, and mass conservation yields a general relation for oxygen transport in hemoglobin solutions. Total oxygen flux is shown to be the sum of the flux in the plasma and the flux due to transport by hemoglobin. The total flux depends not only on oxygen concentration gradient but also on absolute oxygen concentration.