Use the Optic Disc (optic nerve head) as spatial reference

[fischeryann]

• Use the Optic disc as reference for all lenghts (and speeds)
• Optic disc diameter (papila diameter) should be an input parameter

[Zacharie-any]

This is handled by the BloodVolumeRate/PixelSize Parameter for now

[luismuncharazduran]

Optic disc diameter is variable in some pathologies like sickle cell disease (~30% maybe).