Fig. 4
From: Estimating the location and size of retinal injections from orthogonal images of an intact retina
The wedge coordinate system. The coordinate of each point can be found by taking a plane through the nasal pole (N), temporal pole (T) and the point of interest (red dot). The intersection of the plane and the sphere forms an arc (solid arrow and dotted line). The nasotemporal coordinate is the fraction (f) of the distance along the arc from the nasal to the temporal pole. The rim angle (\(\phi _0\)) is used when calculating the wedge coordinates. The dorsoventral coordinate is defined analogously