C.8.26.4.1 Visual Field Static Perimetry Test Measurement Attribute Descriptions

C.8.26.4.1.1 Measurement Laterality

When B (both left and right together) eyes are provided for Measurement Laterality (0024,0113) it shall mean that both eyes are open during the test (binocular). It shall not be used to provide two monocular tests (i.e. one for the left eye and one for the right). Two monocular tests require two SOP Instances and two monocular tests with one binocular test require three SOP Instances.

C.8.26.4.1.2 Foveal Sensitivity

For Foveal Sensitivity (0024,0087), the terminology commonly used for perimetric measurements is employed, with reference to visual thresholds designated by a decibel (dB) scale. The decibel scale for conventional perimetry is based on the maximum stimulus luminance that can be superimposed on a uniform background, and it is given a value of 0 dB of sensitivity. Sensitivity is the inverse of threshold (sensitivity = 1/threshold) and vice versa. In other disciplines, visual threshold is usually defined by the probability of seeing a difference in luminance, brightness, hue or saturation, or a difference in some other attribute exhibited by a given set of stimuli. As such, a threshold is usually described in terms of the minimum amount of luminance, contrast, hue or other attribute that can be minimally detected. However, many sources that refer to perimetry have described threshold in terms of decibel (dB) values rather than attributing the dB measures to sensitivity. It would be advisable to check each individual device to determine how dB is defined.

C.8.26.4.1.3 Blind Spot X and Y Coordinates

For Blind Spot X-Coordinate (0024,0107) and Blind Spot Y-Coordinate (0024,0108), the convention described below for the Cartesian coordinate system specifies that to the right is positive on the x axis and up is positive on the Y axis. Figure C.8.26.4.1-1 illustrates how visual fields are displayed in standard format with the temporal visual field from the right eye displayed to the right and the nasal visual field from the right eye to the left.

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Figure C.8.26.4.1-1 Convention of coordinate system used in visual field representation.