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The Role of Hypoxia in the Limbal Vascular Response to Soft Contact Lens Wear

Purpose. Increases in limbal vascular blood flow frequently occur as an accompaniment to conventional soft contact lens wear. This study attempted to discover whether these changes can be induced by the direct influence of oxygen alone in the absence of contact lenses. Methods. Nine people were subjected to monocular anoxia by bathing one randomly chosen eye with 100% nitrogen using gas-tight goggles. Their other eyes served as controls and were exposed to normal air throughout the study. Vascular changes were quantified by image capture and subsequent analysis, with the change in the proportion of the image corresponding to blood vessels (per area) being used as the measure of hyperemia. Results. Nitrogen-exposed eyes showed significantly greater hyperemia (mean perarea change ± 95% confidence interval, 0.023 ± 0.016 compared with control eyes, −0.013 ± 0.013;P =0.004, paired t test). Conclusion. Reduced oxygen concentration at the ocular surface induces more blood flow in limbal vessels. This result provides further evidence that similar changes occurring during soft contact lens wear are caused by lens-induced hypoxia.