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Laura E. Walter, David A. Quillen, John G. Edwards, D. A. Owens, Gregory R. Jackson; Measurement Error Of The AdaptRx Adaptometer For Healthy Adults and AMD Patients. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3535.
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The purpose of this study was to assess the measurement error (precision) of the AdaptRx (Apeliotus Vision Science, Atlanta, GA). The AdaptRx is a dark adaptometer useful for measuring dark adaptation in patients with a broad range of physiological responses. Basic performance data like measurement error will be useful for the design of future natural history and interventional studies.
Each participant’s dark adaptation was measured twice with the AdaptRx. The second dark adaptation measurement was made two weeks after the first measurement. The speed of each dark adaptation function was characterized by two parameters: the rod-cone break and the rod intercept. The rod-cone break is the time at which rods become more sensitive than cones and is characterized by the classic inflection point in the dark adaptation function. The rod intercept is the time at which visual sensitivity recovers to a criterion level (0.005 scotopic cd/m2). The rod-cone break and the rod intercept were estimated using an unbiased modeling method. Measurement error was calculated using a method based on within standard deviation.
The study sample consisted of 14 adults with normal retinal health (mean age = 47 years, range = 28 to 75 years) and 8 patients with age-related macular degeneration (mean age = 74 years, range 63 to 87 years). The measurement error for the rod-cone break was calculated to be 1.13 minutes. The measurement error for the rod intercept was calculated to be 1.12 minutes. For both the rod-cone break and rod intercept, the variability of the measurement did not change as a function of the magnitude of the parameter. The rod-cone break and rod intercept parameters were highly correlated (r = 0.89, p < 0.0001).
The measurement error (precision) of the AdaptRx is about 1 minute. That is to say, a change of more than 1 minute represents a real change. For comparison, the measurement error of the AdaptRx is slightly better than the Goldmann-Weekers Adaptometer (rod cone break: 1.2 minutes; rod intercept: 1.7 minutes).
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