Ophthalmic Mapping Device Type

(0022,1415)

1

Describes the type of ophthalmic mapping acquisition device. See Section C.8.30.3.1.1 for further explanation.

Corneal Vertex Location

(0046,0202)

1

Location of the corneal vertex. This is used for the reference point for other Attributes within this SOP Instance and determined by the Image referenced in the Attribute Source Image Sequence (0008,2112). Given as column\row. Column is the horizontal offset and row is the vertical offset.

Image relative position specified with sub-pixel resolution such that the origin at the Top Left Hand Corner (TLHC) of the TLHC pixel is 0.0\0.0, the Bottom Right Hand Corner (BRHC) of the TLHC pixel is 1.0\1.0, and the BRHC of the BRHC pixel is Columns\Rows (see Figure C.10.5-1). The values must be within the range 0\0 to Columns\Rows.

This location shall anchor the corneal vertex at the x, y and z coordinates of 0.0, 0.0, 0.0, in mm. See Section C.8.30.3.1.4 for further explanation.

Corneal Topography Surface

(0046,0201)

1

Identifies the surface of the corneal topography map.

Pupil Centroid X-Coordinate

(0046,0203)

1C

The horizontal coordinate of the centroid of the pupil relative to location of the cornea vertex specified in the Attribute Corneal Vertex Location (0046,0202), in mm, such that toward the right is positive. See Section C.8.30.3.1.4 for further explanation.

Required if Attribute Corneal Topography Surface (0046,0201) is A (Anterior).

Pupil Centroid Y-Coordinate

(0046,0204)

1C

The vertical coordinate of the centroid of the pupil relative to location of the cornea vertex specified in the Attribute Corneal Vertex Location (0046,0202), in mm, such that up is positive. See Section C.8.30.3.1.4 for further explanation.

Required if Attribute Corneal Topography Surface (0046,0201) is A (Anterior).

Equivalent Pupil Radius

(0046,0205)

1C

The average physical distance in mm from the pupil centroid specified in the Attributes Pupil Centroid X-Coordinate (0046,0203) and Pupil Centroid Y-Coordinate (0046,0204) to the measured perimeter of the pupil.

Required if Attribute Corneal Topography Surface (0046,0201) is A (Anterior).

Vertices of the Outline of Pupil

(0046,0208)

1C

A set of row/column vertices that outline the perimeter of the pupil.

Two or more pairs of values follow and are the row and column coordinates of the other vertices that outline the perimeter of the pupil. For a two dimensional curve: X1, Y1, X2, Y2, etc. The first (X) dimension corresponds to the image column (horizontal offset), and the second (Y) dimension corresponds to the image row (vertical offset). This is a Polyline and the points are to be interpreted as an n-tuple list of end points between which straight lines are to be drawn.

Required if Attribute Corneal Topography Surface (0046,0201) is A (Anterior).

Include Table C.8.25.10-2 “Keratometric Measurements Macro Attributes”

Minimum Keratometric Sequence

(0046,0215)

1

A sequence that specifies the lowest power obtained when averaging individual meridian.

Only one item shall be permitted.

>Radius of Curvature

(0046,0075)

1

The radius of curvature of the principal meridian of the cornea, measured in mm.

>Keratometric Power

(0046,0076)

1

The refractive power of the cornea at the principal meridian, measured in diopters.

>Keratometric Axis

(0046,0077)

1

The meridian where the keratometric radius of curvature or power is measured, measured in degrees.

Simulated Keratometric Cylinder Sequence

(0046,0218)

1

A sequence that specifies simulated keratometric cylinder power of the corneal surface, measured in diopters.

Only one item shall be permitted.

>Keratometric Power

(0046,0076)

1

The refractive power of the cornea at the principal meridian, measured in diopters.

>Keratometric Axis

(0046,0077)

1

The meridian where the keratometric cylinder or power is measured, measured in degrees.

Average Corneal Power

(0046,0220)

1

The area-corrected average of the corneal power ahead of the entrance pupil, measured in diopters.

Corneal I-S Value

(0046,0224)

1

Quantifies the inferior-superior dioptric asymmetry along the vertical meridian to discriminate Keratoconus, measured in diopters.

Analyzed Area

(0046,0227)

1

The corneal surface area that can be analyzed, measured in mm squared.

Maximum Corneal Curvature Sequence

(0046,0211)

3

A Sequence to convey the maximum curvature and location of the measured corneal topography. Only a single Item is permitted in this sequence.

>Maximum Corneal Curvature

(0046,0212)

1

Maximum curvature in diopters of the measured corneal topography.

>Maximum Corneal Curvature Location

(0046,0213)

1

Location of the corneal maximum curvature.

Given as column\row. Column is the horizontal offset and row is the vertical offset.

Image relative position specified with sub-pixel resolution such that the origin at the Top Left Hand Corner (TLHC) of the TLHC pixel is 0.0\0.0, the Bottom Right Hand Corner (BRHC) of the TLHC pixel is 1.0\1.0, and the BRHC of the BRHC pixel is Columns\Rows (see Figure C.10.5-1). The values must be within the range 0\0 to Columns\Rows.

Surface Regularity Index

(0046,0230)

3

Measures local fluctuations in corneal power (i.e., irregular astigmatism) over the pupil (no units).

Surface Asymmetry Index

(0046,0232)

3

This index sums the meridional mire-to-mire power changes over the entire corneal surface, increasing as topographic irregularities increase (no units).

Corneal Eccentricity Index

(0046,0234)

3

Index used to measure the eccentricity of the cornea (no units).

Keratoconus Prediction Index

(0046,0236)

3

Index used to indicate the presence of Keratoconus (no units)

Decimal Potential Visual Acuity

(0046,0238)

3

The range of best spectacle-corrected distance that might be expected from a functionally normal eye with the topographical characteristics of the analyzed cornea, measured in decimal.

Corneal Topography Map Quality Evaluation

(0046,0242)

1C

Identifies the quality of the topography examination.

Required if a quality rating value exists for the corneal topography map

Corneal Topography Map Type Code Sequence

(0046,0207)

1

The type of corneal topography map encoded in this SOP Instance. It specifies the meaning of the pixel values.

Only a single Item shall be permitted in this sequence.

>Include Table 8.8-1 “Code Sequence Macro Attributes”

Defined CID 4268 “Corneal Topography Map Value Type”

Corneal Topography Mapping Normals Sequence

(0046,0210)

1C

Identifies the data set used for corneal topography mapping values from a normative data base. Required if a normative data base was used.

Only a single Item shall be permitted in this sequence.

>Include Table 10-22 “Data Set Identification Macro Attributes”

Source Image Sequence

(0008,2112)

1

The Image SOP Class/Instance pair of the Image that was used to generate this corneal topography map.

See Section C.8.30.3.1.2 for further explanation.

Only a single Item shall be permitted in this sequence.

>Include Table 10-3 “Image SOP Instance Reference Macro Attributes”

>Purpose of Reference Code Sequence

(0040,A170)

1

Describes the purpose for which the reference is made, (i.e., the role the source image or frame(s) played in the generation of this image). Only a single Item shall be permitted in this sequence.

>>Include Table 8.8-1 “Code Sequence Macro Attributes”

The code used shall be (121322, DCM, "Source image for image processing operation").

Source Image Corneal Processed Data Sequence

(0046,0244)

1

Attributes that contain various power, elevation and wavefront measurements at specific points on the cornea of the SOP Instance referenced in Attribute Source Image Sequence (0008,2112). The Attributes are obtained from measurements of curvature or shape of the cornea. See Section C.8.30.3.1.3 for further explanation.

One or more Items shall be present.

>Corneal Point Location

(0046,0247)

1

The x, y, and z coordinate of a point in the image within the cornea, in mm. Where the origin is conveyed by the Attribute Corneal Vertex Location (0046,0202).

>Corneal Point Estimated

(0046,0248)

1

The point defined in Attribute Corneal Point Location (0046,0247) is an estimated point (i.e., interpolated or extrapolated; not an actual measured point).

>Axial Power

(0046,0249)

1

Conveys corneal shape characteristics, in diopters. It is determined from the curvature, r in mm, of the equivalent sphere with the same slope at a given point on the surface. Axial power = Km/r, where Km is the Keratometric Index.

>Tangential Power

(0046,0250)

1

Determined from the curvature (2nd derivative = d2y/dx2) of a point on the cornea, in diopters; also called Instantaneous Power. Emphasizes irregular astigmatism (large variations in higher order aberrations).

>Refractive Power

(0046,0251)

1

Conveys the optical refraction properties of the cornea, in diopters. It is determined from ray tracing using Snell's Law to calculate the true refractive power.

>Relative Elevation

(0046,0252)

1

Relative elevation, in micrometers, is calculated from the corneal surface distance from a reference surface (i.e., a sphere or ellipsoid) that intersects the corneal vertex. This value is determined from z - z_ref. Where z is conveyed in Attribute Corneal Point Location (0046,0247) and z_ref is the elevation of the reference surface.

>Corneal Wavefront

(0046,0253)

1

Corneal wavefront, in micrometers, is calculated from the elevation data by fitting with the Zernike Series expansion.