C.8.25.14 Ophthalmic Axial Measurements Module
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#### C.8.25.14 Ophthalmic Axial Measurements Module

Table C.8.25.14-1 defines the Attributes used to encode axial measurements of the eye made by an axial measurements device. This is typically done for both eyes, but may be for just one.

Table C.8.25.14-1. Ophthalmic Axial Measurements Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Ophthalmic Axial Measurements Device Type | (0022,1009) | 1 | Describes the type of ophthalmic axial measurement acquisition device. Defined Terms: ULTRASOUND OPTICAL
Ophthalmic Ultrasound Method Code Sequence | (0022,1044) | 1C | The method used for obtaining axial measurements of the eye. Only a single Item shall be included in this Sequence. Required if Ophthalmic Axial Measurements Device Type (0022,1009) is ULTRASOUND.
>Include Table 8.8-1 “Code Sequence Macro Attributes” | >Defined CID 4230 “Ophthalmic Ultrasound Axial Measurements Type”
Anterior Chamber Depth Definition Code Sequence | (0022,1125) | 3 | The definition of anterior chamber depth for this instrument. Only a single Item is permitted in this Sequence.
>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 4239 “Anterior Chamber Depth Definition”
Ophthalmic Axial Measurements Right Eye Sequence | (0022,1007) | 1C | Axial measurements of a patient's right eye. Only a single Item shall be included in this Sequence. Required if the right eye is measured. ### Note If Ophthalmic Axial Measurements Right Eye Sequence (0022,1007) is present, Measurement Laterality (0024,0113), if present, will have a value of R or B as appropriate.
>Include Table C.8.25.14-2 “Ophthalmic Axial Measurements Macro Attributes” |
>Include Table C.8.25.14-5 “Ophthalmic Axial Measurements Selected Macro Attributes” |
Ophthalmic Axial Measurements Left Eye Sequence | (0022,1008) | 1C | Axial measurements of a patient's left eye. Only a single Item shall be included in this Sequence. Required if the left eye is measured. ### Note If Ophthalmic Axial Measurements Left Eye Sequence (0022,1008) is present, Measurement Laterality (0024,0113), if present, will have a value of L or B as appropriate.
>Include Table C.8.25.14-2 “Ophthalmic Axial Measurements Macro Attributes” |
>Include Table C.8.25.14-5 “Ophthalmic Axial Measurements Selected Macro Attributes” |

##### C.8.25.14.1 Ophthalmic Axial Measurements Macro

Table C.8.25.14-2 describes the attributes for the Ophthalmic Axial Measurements Macro.

Table C.8.25.14-2. Ophthalmic Axial Measurements Macro Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Lens Status Code Sequence | (0022,1024) | 1 | Lens status of the eye. See Section C.8.25.14.1.1.1 for further explanation. Only a single Item shall be included in this Sequence.
>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 4231 “Lens Status”
Lens Status Description | (0022,1065) | 3 | A free form text description of Lens Status (0022,1024).
Vitreous Status Code Sequence | (0022,1025) | 1 | Status of the vitreous cavity. See Section C.8.25.14.1.1.2 for further explanation. Only a single Item shall be included in this Sequence.
>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 4232 “Vitreous Status”
Vitreous Status Description | (0022,1066) | 3 | A free form text description of Vitreous Status (0022,1025).
Pupil Dilated | (0022,000D) | 2 | Whether or not the patient's pupils were pharmacologically dilated for this acquisition Enumerated Values: YES NO If this tag is empty, no information is available.
Degree of Dilation | (0022,000E) | 2C | The degree of the dilation in mm. Required if the value of Pupil Dilated (0022,000D) is YES.
Mydriatic Agent Sequence | (0022,0058) | 2C | Information about the agent administered. Zero or more Items shall be included in this Sequence. ### Note An empty sequence indicates that an agent was used for dilation, but the name was not entered. Required if the value of Pupil Dilated (0022,000D) is YES.
>Mydriatic Agent Code Sequence | (0022,001C) | 1 | The actual agent administered to dilate the pupil. Only a single Item shall be included in this Sequence.
>>Include Table 8.8-1 “Code Sequence Macro Attributes”. | Baseline CID 4208 “Mydriatic Agent”.
>Mydriatic Agent Concentration | (0022,004E) | 3 | The concentration of the agent.
>Mydriatic Agent Concentration Units Sequence | (0022,0042) | 1C | Units of measure for the Mydriatic Agent Concentration. Only a single Item shall be included in this Sequence. Required if Mydriatic Agent Concentration (0022,004E) is present.
>>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 4244 “Ophthalmic Agent Concentration Units”
Ophthalmic Axial Length Measurements Sequence | (0022,1050) | 1 | Measurements of the axial length of a patient's eye. One or more Items shall be included in this Sequence.
>Ophthalmic Axial Length Measurements Type | (0022,1010) | 1 | Identifies whether measuring the total axial length of the patient's eye or a segment of the eye for which a discrete measurement was obtained. Enumerated Values: TOTAL LENGTH the total axial length was taken with one measurement LENGTH SUMMATION a summation of segmental lengths that determine the total axial length SEGMENTAL LENGTH a segmental axial length
>Ophthalmic Axial Length Measurements Total Length Sequence | (0022,1210) | 1C | The axial length of a patient's eye, in mm. One or more Items shall be included in this Sequence. Required if Ophthalmic Axial Length Measurements Type (0022,1010) is TOTAL LENGTH. See Section C.8.25.14.1.1.4 for further explanation.
>>Ophthalmic Axial Length | (0022,1019) | 1 | The axial length measurement acquired, in mm. The type of measurement is specified in the Ophthalmic Axial Length Measurements Type (0022,1010). See Section C.8.25.14.1.1.3 and Section C.8.25.14.1.1.4 for further explanation.
>>Ophthalmic Axial Length Measurement Modified | (0022,1140) | 1 | Whether or not the clinician intervened to modify the output of the device. For example by forcing it to select a different peak in the display. Enumerated Values: YES NO
>>Referenced Ophthalmic Axial Length Measurement QC Image Sequence | (0022,1330) | 1 | Reference to the quality control image associated with this measurement. Only a single Item shall be included in this Sequence. See Section C.8.25.14.1.1.6 for further explanation.
>>>Include Table C.8.25.16-6 “Ophthalmic Axial Measurements Quality Image SOP Instance Reference Macro Attributes” |
>>Include Table C.8.25.14-4 “Ophthalmic Axial Measurements Related Information Macro Attributes” |
>Ophthalmic Axial Length Measurements Length Summation Sequence | (0022,1212) | 1C | Axial length of a patient's eye, in mm, when it is calculated by summation of multiple segmental axial length measurements. One or more Items shall be included in this Sequence. Required if Ophthalmic Axial Length Measurements Type (0022,1010) is LENGTH SUMMATION. See Section C.8.25.14.1.1.4 for further explanation.
>>Ophthalmic Axial Length | (0022,1019) | 1 | The axial length measurement acquired, in mm. The type of measurement is specified in the Ophthalmic Axial Length Measurements Type (0022,1010). See Section C.8.25.14.1.1.3 and Section C.8.25.14.1.1.4 for further explanation.
>>Ophthalmic Axial Length Measurement Modified | (0022,1140) | 1 | Whether or not the clinician intervened to modify the output of the device. For example by forcing it to select a different peak in the display. Enumerated Values: YES NO
>>Referenced Ophthalmic Axial Length Measurement QC Image Sequence | (0022,1330) | 1 | Reference to the quality control image associated with this measurement. Only a single Item shall be included in this Sequence. See Section C.8.25.14.1.1.6 for further explanation.
>>>Include Table C.8.25.16-6 “Ophthalmic Axial Measurements Quality Image SOP Instance Reference Macro Attributes” |
>>Ophthalmic Axial Length Measurements Segmental Length Sequence | (0022,1211) | 1 | Segmental axial length measurements of a patient's eye that contribute to an aggregate axial length measurement. One or more Items shall be included in this Sequence. See Section C.8.25.14.1.1.4 for further explanation.
>>>Include Table C.8.25.14-3 “Ophthalmic Axial Length Segmental Measurements Macro Attributes” |
>Ophthalmic Axial Length Measurements Segmental Length Sequence | (0022,1211) | 1C | Segmental axial length measurement of a patient's eye. Only a single Item shall be included in this Sequence. Required if Ophthalmic Axial Length Measurements Type (0022,1010) is SEGMENTAL LENGTH. See Section C.8.25.14.1.1.4 for further explanation.
>>Include Table C.8.25.14-3 “Ophthalmic Axial Length Segmental Measurements Macro Attributes” |

###### C.8.25.14.1.1 Ophthalmic Axial Measurements Macro Attribute Descriptions

###### C.8.25.14.1.1.1 Lens Status Code Sequence

Lens Status Code Sequence (0022,1024) refers to either the natural lens of the eye (phakic), or various types of lens implants inserted in cataract surgery, or lack of a lens in the eye (aphakic).

###### C.8.25.14.1.1.2 Vitreous Status Code Sequence

Vitreous Status Code Sequence (0022,1025) refers to either the natural status of the vitreous cavity (vitreous only) or to various possible states after vitreous surgery.

###### C.8.25.14.1.1.3 Ophthalmic Axial Length

If Ophthalmic Axial Measurements Device Type (0022,1009) is ULTRASOUND, the Ophthalmic Axial Length (0022,1019) measurement is taken from the anterior vertex of the cornea to the anterior surface of the retina (internal limiting membrane).

If Ophthalmic Axial Measurements Device Type (0022,1009) is OPTICAL, the Ophthalmic Axial Length (0022,1019) measurement is taken from the anterior vertex of the cornea to the level of the photoreceptors in the retina and compensated to adjust for the thickness of the retina to mimic the ultrasound technique.

This difference is an inherent property of the measurement method. Since optical devices measure to retinal pigment epithelium and ultrasound devices measure to internal limiting membrane, the difference must be subtracted to obtain comparable results for use in intraocular lens calculation formulas. The difference is the thickness of the retina, which has been determined empirically and varies with the axial length of the eye.

The intent is to measure along the patient's visual axis.

###### C.8.25.14.1.1.4 Ophthalmic Axial Length Measurements Segment Name Code Sequence

When the acquisition device type is ultrasound, the Ophthalmic Axial Length (0022,1019) may represent distance calculated using a single time value and an average presumed velocity for the entire eye. Alternatively it may represent the sum of multiple segmental axial length measurements with each distance value calculated using a different time value and a presumed velocity specific to that segment of the eye.

When the acquisition device type is optical, the whole length can be measured instead of measuring and summing up different segments of the eye. Nevertheless, optical axial measurement devices can also measure segments of the eye independently(e.g., the Anterior Chamber depth).

Each segment of the eye that is measured shall be identified by the Ophthalmic Axial Length Measurements Segment Name Code Sequence (0022,1101).

###### C.8.25.14.1.1.5 Observer Type

For attribute Observer Type (0040,A084), Ultrasound axial length measurement devices take many measurements in rapid sequence. The machine can be set to select a good quality measurement automatically, or it can be set so that the user presses a footswitch when he/she sees a quality measurement based on the graphical display.

###### C.8.25.14.1.1.6 Referenced Ophthalmic Axial Length Measurement QC Image Sequence

The attribute Referenced Ophthalmic Axial Length Measurement QC Image Sequence (0022,1330) references a quality control image that is a secondary capture of the presentation of a one dimensional waveform produced when performing ophthalmic axial measurements. It is acquired by the modality creating the ophthalmic axial measurements. The purpose of these images is to judge the quality of an axial length measurement for use in calculating the power of intraocular lens to place in a patient's eye in cataract surgery. The image is used for quality control and not for diagnostic purposes. See PS3.17.

The SOP Instance for the quality control image will meet the following requirements:

- Frame Increment Pointer (0028,0009) is set to 00182002 = sequencing by Frame Label Vector (0018,2002).

  ### Note

  The frame number is the recommended value for the label.

- The attribute Reference Instance Sequence (0008,114A) is conveyed and only a single item is used. The item in Reference Instance Sequence (0008,114A) contains the value "1.2.840.10008.5.1.4.1.1.78.7" = (this SOP Class) for attribute Referenced SOP Class UID (0008,0050) and attribute Reference SOP Instance UID (0008,1155) will reference this measurement SOP Instance.

- Burned In Annotation (0028,0301) is set to NO.

  The attribute Burned In Annotation (0028,0301) defines whether patient demographics have been burned into the image. This attribute does not prohibit non-demographic burned in annotation, such as position of gates, for image or waveform annotations that are very important to a user. Such annotations are expected to be conveyed and displayed.

- Quality Control Image (0028,0300) is set to YES.

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