Soft contact lens wear at altitude: effects of hypoxia

In the U.S. Air Force, aircraft can be divided into two categories--those with cabin pressures equivalent to high altitudes and aircraft with cabin pressures equivalent to lower altitudes, with longer duration exposures. The purpose of this study was to determine the effects of soft contact lens wear under atmospheric pressures simulating these two types of aircraft environments. Ten subjects were tested to 7620 m (25,000 ft) in hypobaric chamber flights of 75 min and eight subjects were tested in hypobaric chamber flights at 3048 m (10,000 ft) for 4 h. Four subjects were also tested in dry air to further simulate cabin conditions. Vision and physiologic response were monitored by measurements of visual acuity, contrast sensitivity, and slit-lamp biomicroscopy examinations. The results of this study indicate that the physiologic responses of the cornea to soft contact lens wear at altitude are subject to higher levels of manifested stresses, but these occurred without measurable degradation in vision and did not preclude normal wear of soft contact lenses.