Short Wavelength and Frequency Doubling Technology Perimetry
Short Wavelength Automated Perimetry (SWAP) is based on the principal to evaluate different retinal ganglion cells population. SWAP detects the visual field defects by testing sensitiveness to short—wavelength (blue-yellow light) by isolating S cone system and reducing the participation of other cone systems (red—long wavelength, green—medium wavelength). SWAP uses the same perimeter, blue 440 nm narrow band stimulus on yellow screen to selectively activate the short—wavelength cones and small ganglion cells. Test is performed within 30° of the visual field. Unfortunately this type of perimetry is influenced by media opacity (cataract), so is not routinely performed .