• We noted that the adjustable fixation device present on some models of the Goldmann-Weekers dark adaptometer has a calibration error that results in a consistent and predictable overestimation of retinal eccentricity. The error occurs because the eye being tested is not in the geometric center of the projection sphere. The true retinal locus may be computed by trigonometric analysis. A conversion table is available for reference.
Maggiano JM, Fishman GA, Evans LS, Sieving P, Goldbaum M. Calibration Error in Dark Adaptometer. Arch Ophthalmol. 1978;96(6):1082-1083. doi:10.1001/archopht.1978.03910050602024