Normal Aging Effects for Two Forms of Frequency Doubling Technology (fdt) Perimetry Using a 24-2 Stimulus Presentation Pattern

Abstract

Abstract: : Purpose: To compare normal aging effects using two different forms of Frequency Doubling Technology (FDT) perimetry, with smaller targets and a 24-2 stimulus pattern. One method uses the Quadravision test procedure (QFDT), while the other is a prototype being developed for commercial purposes (FDT2). The two procedures incorporate different stimulus backgrounds, stimulus sizes, target locations and threshold test strategies. Methods: Normal observers had to be between the ages of 18 and 85, have a normal anterior segment and posterior pole examination, normal visual fields for standard automated perimetry (SAP), no prior history of ocular disease or surgery, no history of systemic disease that could affect vision, visual acuity of better than 20/40, refractive errors of less than 5 D and less than 2 D of cylinder and could not be taking any medications known to affect vision OU. QFDT uses a 50 cd/m2 background luminance, a Modified Binary Search [MOBS] test procedure, and 4 degree diameter targets and a 24-2 stimulus presentation pattern. FDT 2 uses a 100 cd/m2 background, a ZEST (maximum liklihood) test strategy, 5 degree diameter targets and a pattern that is slightly different from a 24-2 stimulus presentation pattern. Both tests utilize a sinusoidal spatial frequency of 0.5 cycles/ degree and a counterphase flicker rate of 18 Hz. One hundred normal observers were tested with QFDT, and 101 normal subjects were tested with FDT2. Results: For stimuli within 15 degrees radius, both QFDT and FDT2 show linear effects of aging (approximately 0.6 dB loss per decade) that are similar to those obtained for the commercial version of FDT incorporating 17 or 19 large targets. Outside of 15 degrees, QFDT shows a larger aging effect (about 1.0 to 1.2 dB per decade) than FDT 2 (about 0.8 dB per decade). Conclusions: Aging effects (0.6 dB per decade) for the central visual field of both 24-2 FDT procedures were similar to earlier findings for the original FDT device. Outside 15 degrees, aging effects were greater for QFDT than for FDT 2. Differences in stimulus size and test duration account for the majority of these variations in aging effects for QFDT and FDT 2.

Keywords: visual fields • aging: visual performance • aging