Appendix

This appendix keeps reference material separate from the main workflow pages.

Keyboard shortcuts

The list below reflects the current shortcut registrations in the GUI.

View and overlay controls

Action	Shortcut
Show artery overlay	1
Show optic-disc overlay	2
Show vein overlay	3
Show all vessels	4
Show all masks	5
Hide mask overlay	6
Change mask opacity	Ctrl + Scroll
Fit the current view	Double-click in the canvas

Editing tools

Action	Shortcut
Brush	B
Smart paint	Shift + B
Eraser	E
Swap artery/vein classification	C
Fovea location tool	F
Increase brush size	=
Decrease brush size	-
Change brush size	Shift + Scroll
Save edits	Ctrl + S
Undo	Ctrl + Z
Redo	Ctrl + Shift + Z
Temporary pan while editing	Hold Space

Navigation

Action	Shortcut
Previous image	Left Arrow
Next image	Right Arrow

Metric definitions

The tables below describe the current metric families documented by the active calculators. Metric availability depends on the presence of the required landmarks, ROI selection, and geometry support.

Note

Geometry-dependent metrics such as disc_area_mm2, *_area_mm2, *_density_area, and geodesic distance conversions may be skipped when the geometry backend is unavailable or incomplete.

Landmark metrics

These are image-level metrics that do not depend on the selected ROI combination.

Metric key	Description
laterality	Eye laterality inferred from the disc-fovea relationship.
disc_center_x, disc_center_y	Optic-disc center coordinates in image space.
disc_area_px	Optic-disc area in pixels.
disc_area_mm2	Optic-disc area in square millimetres when geometry area support is available.
disc_diameter_px, disc_diameter_um	Equivalent optic-disc diameter in pixels and micrometres.
disc_major_axis_px, disc_major_axis_um	Major axis of the fitted optic-disc ellipse in pixels and micrometres.
disc_minor_axis_px, disc_minor_axis_um	Minor axis of the fitted optic-disc ellipse in pixels and micrometres.
disc_orientation_deg	Orientation of the fitted optic-disc ellipse in degrees.
disc_circularity	Circularity estimate for the optic-disc region.
disc_eccentricity	Eccentricity of the fitted optic-disc ellipse.
fovea_center_x, fovea_center_y	Fovea coordinates saved for the current image.
disc_fovea_distance_px, disc_fovea_distance_um	Disc-to-fovea distance in pixels and micrometres.
disc_fovea_angle_deg	Angle between the disc and fovea reference line.

ROI definitions

ROI-dependent metrics are currently organized around these definitions:

ROI code	Display name	Purpose
full	Full image	Whole-image vessel summary.
central	Central retina	Central retinal measurements around the optic-disc landmark.
mid_periphery	Mid-periphery	Template-based mid-peripheral measurements.

ROI metric key patterns

For ROI-dependent metrics, the calculators use three prefixes:

• vessel_ for all vessels combined

• a_ for arteries only

• v_ for veins only

The current key families are:

Metric pattern	Description
*_density	Vessel-pixel fraction inside the active ROI.
*_fractal_dimension_sandbox	Fractal dimension estimated with the sandbox method.
*_fractal_dimension_boxcount	Fractal dimension estimated with box counting.
*_area_mm2	Vessel area in square millimetres when geometry area support is available.
*_density_area	Vessel area divided by ROI area when both geometry areas are available.
*_tortuosity_density	Mean density-style tortuosity measure across extracted vessel paths.
*_tortuosity_distance	Mean chord-versus-curve tortuosity measure across extracted vessel paths.
*_width_px	Mean vessel width in pixels.
*_width_um	Mean vessel width in micrometres.
*_width_gradient_px	Linear width gradient in image space.
*_width_gradient_um	Linear width gradient in real-space micrometres.
*_width_intercept_px	Linear width-fit intercept in pixels.
*_width_intercept_um	Linear width-fit intercept in micrometres.

Relationship metrics

Metric key	Description
av_ratio	Ratio of artery density to vein density when both are available.
av_crossings	Number of artery-vein crossings estimated from overlapping skeleton pixels.
av_arcade_concavity	Central-ROI arcade concavity estimate when the necessary landmarks and vessel data are available.

Notes on exported workbooks

• Landmark metrics are saved once per image.

• ROI metrics are saved per ROI selection.

• Some database columns may remain empty when the corresponding landmarks or geometry operations are unavailable for a given image.