Short wavelength automated perimetry (SWAP) in ophthalmic practice

Short Wavelength Automated Perimetry (SWAP) uses a two-color increment threshold procedure (blue-on-yellow) to assess the functional status of short-wavelength-sensitive (SWS) mechanisms. This functional test has been shown to detect visual field abnormalities in patients at high risk of developing glaucoma and in patients with optic neuritis when standard (white-on-white) visual fields are still within normal limits. Often times, damage uncovered by SWAP precedes standard field loss by three or more years. SWAP also reveals a greater spatial extent of visual field damage in glaucoma patients than standard perimetry and can herald progression of standard visual field damage into the areas already classified as abnormal by SWAP.

This paper describes the SWAP technique and briefly discusses the current theories that account for SWAP's ability to detect visual field damage at an earlier stage than standard perimetry. Several cases that demonstrate the usefulness of this technique are reported.

SWAP testing appears to be the most sensitive functional test for early detection of glaucomatous damage currently available. Although SWAP testing has a few disadvantages, none of them significantly restrict the clinical application of SWAP for glaucoma evaluation.