Contrast Sensitivity

Bailie-Lovie Test Chart 100%

Bailie-Lovie Test Chart 10%

Contrast is the difference in luminance between two objects as seen by an individual and this is an important component in the ‘real’ visual world. Contrast sensitivity (CS) tests, therefore, have the ability to provide an assessment of this aspect of visual perception and provide a better understanding of an individual’s true functional vision.

Assessing contrast sensitivity function (CSF) can be difficult compared to the measurement of visual acuity, but it can be useful as some patients can have near normal VA (visual acuity), but still complain of visual difficulties due to poor CSF.

The two tests can be equated and a simple practical example of this is the Bailie-Lovie Test Chart where a 100% contrast (black against white) assessment is compared with a 10% (grey against white) chart.

There are also a number of eye conditions that will have an impact on contrast sensitivity such as cataract and age related macular degeneration.

In the practical sense a loss or decrease in contrast sensitivity function could be very relevant, especially in poorly-lit surroundings (e.g. when a step or torn piece of carpet might not be noticed, and could lead to a trip or fall with the potential for injury).

In certain circumstances contrast strips on steps and doors can help people with visual impairment, allowing them to appreciate the ‘edge’ of a surface. For example, hospitals often now have strongly-coloured lines on walls or floors, leading people to various departments, and in public places, the edges of steps are often painted bright yellow, as are the handles on buses.