Confirming SAP results with further test is the best way to diagnose VF abnormalities

It is best to confirm visual field (VF) abnormality as shown by Standard Automated Perimetry (SAP) with either a further SAP test or a Short-Wavelength Automated Perimetry (SWAP) test, concluded a study published in the March 2009 issue of Investigative Ophthalmology and Visual Science.

Professor Robert Weinreb of the Hamilton Glaucoma Center and Department of Ophthalmology, University of California at San Diego, US and colleagues evaluated data from glaucomatous (n=174) and healthy (n=164) eyes, each with reliable 24-2 SAP-SITA, SWAP-SITA and Matrix FDT tests. The researchers created three definitions of VF abnormality: single-test abnormality, abnormality as confirmed by repeating the same test, and abnormality as confirmed by conducting a second, different, test. Using these three abnormality definitions, the team assessed each test’s sensitivity, the agreement between tests, the deficit locations and machine-generated pattern standard deviation (PSD) to compare the testing methods.

Professor Weinreb’s team discovered that single tests of SAP, SWAP and FDT had sensitivities of 30%, 29% and 28%, respectively. When confirming the abnormality with the same test, sensitivities were 24–27%; when confirming with a different test, the sensitivity range was 20–23%. The sensitivities of the combinations of different tests were all lower than the SAP/SAP test, and the sensitivities of the same-tests were higher than that of the SWAP/FDT test.

Therefore the team concluded that it is important to confirm a diagnosis of VF abnormality on SAP by subsequently testing again, either with SAP or SWAP.