The effect of induced intraocular straylight on perimetric tests.

PURPOSE To investigate the effect of intraocular straylight (IOS) on threshold measurements made by four types of perimetry: standard automated perimetry (SAP), frequency-doubling technology (FDT) perimetry, flicker-defined form (FDF) perimetry, and the Moorfields Motion Displacement Test (MDT). METHODS Six healthy young (21-29 years) psychophysically experienced observers were tested five times with each perimeter, each time with one of five different white opacity filters (WOFs), to induce various levels of IOS. Each WOF gave rise to an increase in IOS, measured with a straylight meter, of between 10% and 200% from baseline and ranging in effect from normal ageing to significant cataract. The change in sensitivity from baseline was normalized, allowing comparison of standardized (z) scores (change divided by the standard deviation of normative values) for each instrument. RESULTS Average SAP, FDT, and FDF thresholds were significantly affected (P < 0.001) by moderate to large increases in IOS (50%-200%), whereas MDT remained largely unaffected over the same range of straylight levels. CONCLUSIONS The Moorfields MDT shows greater resilience to the effects of additional straylight compared with SAP, FDT, or FDF.