kontrasztképesség

Kontrasztképesség, often translated as contrast sensitivity, is a measure of an individual's ability to perceive differences in luminance or brightness within a visual scene. It quantifies how well the eye can distinguish an object from its background, especially when the difference in brightness is small. This is a critical aspect of visual function, as it directly impacts our ability to see clearly and navigate our environment effectively.

Unlike visual acuity, which measures the ability to discern fine details at a specific distance, contrast sensitivity assesses the ability to detect gradual changes in brightness. Low contrast sensitivity means an individual may struggle to see objects that do not stand out sharply from their surroundings, even if they are otherwise large enough to be seen by standard visual acuity tests. This can lead to difficulties in various situations, such as reading text with low contrast, recognizing faces in dim lighting, or driving at dusk.

Several factors can affect contrast sensitivity, including the health of the eyes, particularly the clarity of the cornea and lens, and the function of the retina and optic nerve. Conditions such as cataracts, glaucoma, diabetic retinopathy, and even simple aging can reduce contrast sensitivity. Furthermore, the lighting conditions under which a visual task is performed play a significant role. Good lighting generally enhances contrast sensitivity, while poor lighting can diminish it.

Testing contrast sensitivity typically involves using charts with progressively lower contrast patterns, such as gratings of varying spatial frequencies. The lowest contrast level at which a person can still detect the pattern is recorded, providing a measure of their contrast sensitivity function. This measurement is valuable in diagnosing and monitoring various eye diseases and can inform decisions about visual rehabilitation and environmental modifications to improve visual performance.