Abstract
Purpose: :
To compare the outcome and the reproducibility of MPOD testing with two HFP-based method, a standard, well established instrument (MaculaMetrics, Rehoboth, MA) and the QE (ZeaVision, Chesterfield, MO).
Methods: :
Eighteen White volunteers (age range: 50-66 yo; M/F=7/11) completed a test-retest session within 3 weeks. MPOD was tested 0.5-deg from the fovea (MPOD-0.5). With the Std-HFP method, a stimulus at 460nm in counter-phase with a 570nm one, referenced to a 7-deg eccentricity peripheral target was used (Iannaccone et al. IOVS 2007; 48: 1458-65). Unlike the Std-HFP method, with the QE observers respond to flicker appearance to a 470nm stimulus in counter-phase with a 540nm one, the peripheral reference value is estimated automatically by the device based on age-specific normative data obtained at 8-deg eccentricity, and stimuli are presented on a white photopic (250 cd/m2) background. Pearson’s coefficients, r, and coefficients of variation (CV) were calculated to estimate the correlation between, and the reproducibility of the two instruments. Since measurements between eyes were highly correlated, analyses were performed on inter-ocular averages.
Results: :
The mean MPOD-0.5 was 0.40 (±0.16, SD) by Std-HFP and 0.38±0.16 with the QE. Correlation between the two methods was very high (r = 0.818). The CV was 6.5±5.8% with the QE and 3.8±3.1% with the Std-HFP. The latter CV compares very favorably with our previous experience in elderly >70 yo (18.4%, Gallaher et al. Vis. Res. 2007; 47: 1253-59). The mean MPOD-0.5 testing time for both eyes was 10.7±5.2 min with the QE, which is 1/3 of the time required by Std-HFP (30.7±15.2 min; p=0.00009).
Conclusions: :
Both instruments provided MPOD-0.5 estimates in this age range that were highly reproducible and strongly correlated with one another. Because of its shorter duration, the QE instrument appears especially suitable for the measurement of MPOD-0.5 values in large-scale clinical or epidemiological settings.
Keywords: macular pigment • clinical (human) or epidemiologic studies: systems/equipment/techniques