Effects of hypoxia on color vision with emphasis on the mesopic range

Abstract

The ability to see clear images, to resolve fine spatial detail in faint objects, to see and appreciate small color differences, to discriminate motion direction and to detect rapidly flickering lights over a very large range of natural illumination is something we often take for granted. Good vision is our expectation, but as we grow older, we become aware of very gradual visual deficits that in some cases can lead to severe loss of vision. These deficits are often caused by changes in the optics of the eye and/or the retina. A normal supply of oxygen and nutrients to the retina is essential to maintain good vision, but when the supporting mechanisms fail, local hypoxia can trigger structural changes that affect normal vision. In this article, we review endogenous and exogenous factors that cause changes in the supply of oxygen to the eye and how these can affect color vision when oxygen demands vary with light adaptation level. We review the latest color vision assessment techniques and show how the level of retinal oxygenation can affect color vision in normal trichromats and in subjects with congenital color deficiencies. We also discuss acquired loss of color vision in relation to hypoxia and how it may soon become possible to use advanced vision and optometric tests to detect the earliest signs of disease that precede clinical diagnosis and to monitor disease progression and effectiveness of treatment. We explore how knowledge of normal differences between photopic and mesopic visual performance and the expected limits of normal variability as a function of age can help achieve this goal.