Table C.8.26.4-1 defines the Attributes used to represent the test measurement values determined during a patient's visual field test.
Table C.8.26.4-1. Visual Field Static Perimetry Test Measurements Module Attributes
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Laterality of body part (eye) examined. See Section C.8.26.4.1.1 for further explanation. |
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Whether the device was able to determine presented visual stimuli. |
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The total number of visual stimuli presented to the patient. This includes the number of stimuli repetitions. Required if Presented Visual Stimuli Data Flag (0024,0037) is YES. |
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Total time the visual field machine was actively presenting visual stimuli to patient, in seconds. |
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Foveal Sensitivity is the reciprocal of foveal threshold (1/foveal threshold), in dB. Foveal Threshold is the minimum amount of luminance increment on a uniform background that can be detected by the patient at coordinates 0,0 (relative to the center of the patient's fixation). See Section C.8.26.4.1.2 for further explanation. Required if the value for Foveal Sensitivity Measured (0024,0086) is YES. |
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Existence of normative data base for the foveal point sensitivity. |
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The percentile of the foveal point sensitivity within an age corrected normal visual field, in percent. Required if the value for Foveal Sensitivity Measured (0024,0086) is YES and Foveal Point Normative Data Flag (0024,0117) is YES. |
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Information about the starting luminance screening values. One or more Items shall be included in this Sequence. Required if the value for Screening Baseline Measured (0024,0120) is YES. |
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Method used to determine starting luminance screening values. |
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The horizontal coordinate of the patient's blind spot relative to the center of the patient's fixation, in degrees, such that toward the right is positive. Required if the value for Blind Spot Localized (0024,0106) is YES. See Section C.8.26.4.1.3 for further explanation. |
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The vertical coordinate of the patient's blind spot relative to the center of the patient fixation, in degrees, such that up is positive. Required if the value for Blind Spot Localized (0024,0106) is YES. See Section C.8.26.4.1.3 for further explanation. |
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The minimum sensitivity value generated by the equipment used for this visual field test, in dB. |
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Existence of normative data base for at least one of the test points in this set of test points. |
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Normative data base used for this test sequence. Only a single Item shall be included in this Sequence. Required if Test Point Normals Data Flag (0024,0057) is YES. |
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>Include Table 10-22 “Externally-Sourced Data Set Identification Macro Attributes” |
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Software algorithm used to provide the probability that the age corrected sensitivity deviation values at each test point belong to a normal visual field. Only a single Item shall be included in this Sequence. Required if Test Point Normals Data Flag (0024,0057) is YES. |
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>Include Table 10-19 “Algorithm Identification Macro Attributes” |
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Software algorithm used to provide the probability that the sensitivity deviation values at each test point belong to a normal visual field. Only a single Item shall be included in this Sequence. Required if Test Point Normals Data Flag (0024,0057) is YES. |
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>Include Table 10-19 “Algorithm Identification Macro Attributes” |
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The horizontal coordinate of a single test point relative to the center of the patient fixation, in degrees, such that toward the right is positive. |
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The vertical coordinate of a single test point relative to the center of the patient fixation, in degrees, such that up is positive. |
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Whether the patient saw a stimulus presented at a luminance other than maximum, a presentation at maximum luminance, or did not see any presented stimulus. Enumerated Values: |
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If Stimulus Results (0024,0093) is SEEN then this value is the sensitivity, in dB. Required if Content Item Modifier Sequence (0040,0441) within Performed Protocol Code Sequence (0040,0260) contains an Item with the value (261004008, SCT, "Diagnostic"). May be present otherwise. |
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Whether the retested stimulus presented was seen by the patient. |
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If the Retest Stimulus Seen (0024,0095) is YES, then this value is the sensitivity, in dB. |
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Difference between the expected and the determined sensitivity, each in dB. |
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Information about normal values for each visual field test point. Zero or more Items shall be included in this Sequence. May be empty if there is no normative data for this test point. Required if Test Point Normals Data Flag (0024,0057) is YES. |
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Difference between the patient's local sensitivity and the age corrected normal sensitivity, in dB. |
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The percentile of the age corrected sensitivity deviation within the normal population of visual field, in percent. |
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Whether generalized defect corrected data are available for this point. |
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The age corrected sensitivity deviation after correction for the Generalized Defect, in dB. Generalized defect is proportional to the loss in sensitivity shared by all points in the visual field. Required if Generalized Defect Corrected Sensitivity Deviation Flag (0024,0102) is YES. |
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>>Generalized Defect Corrected Sensitivity Deviation Probability Value |
The percentile of the generalized defect corrected sensitivity deviation within the normal population of visual field, in percent. Required if Generalized Defect Corrected Sensitivity Deviation Flag (0024,0102) is YES. |
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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.
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.
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.
