Swap perimetry

SWAP perimetry

SWAP perimetry stands for short-wavelength automated perimetry and is a visual field test that uses blue stimuli on a bright yellow background to examine how well the short-wavelength (blue) sensitive cones and their pathways are functioning. By bathing the eye in a yellow background, the test suppresses the responses of the long- and medium-wavelength cones so the blue-sensitive system stands out, making it easier to detect subtle losses in that pathway. This method was developed because certain eye conditions can affect these blue-yellow pathways early, so SWAP can sometimes reveal early damage that standard white-on-white tests miss. During the test you look at a fixation point while brief blue spots appear in different parts of your peripheral vision and you indicate when you see them. The test can be more demanding than routine tests because the stimuli are dimmer and the bright background can be tiring, which means it may take longer and be less comfortable for some patients. Another important limitation is that aging lenses and cataracts filter blue light, which can make results harder to interpret, so clinicians must account for lens status. Because of its sensitivity and variability, results are best used together with other clinical findings and tests. SWAP matters because it provides an additional way to detect early changes in the visual system, helping guide earlier intervention or closer monitoring when standard tests appear normal. Clinicians may choose SWAP for patients where early damage is suspected or when they want a different perspective on visual function, but they balance its benefits against issues of patient comfort, test duration, and optical factors that influence blue light transmission.