Drusen Field: a Reaction-Diffusion Map of Dry AMD

This is the 2D-native counterpart to the 3D drusen simulator. Instead of instanced spheres growing and merging beneath a deformable membrane, it solves a reaction–diffusion equation for a deposit-concentration field on a grid under the macula: every cell obeys the same deposition-minus-clearance rate law as a single drusen, while a diffusion term lets nucleated deposits spread laterally and coalesce purely by field overlap. A live en-face heatmap shows the whole macula from above; a radial cross-section plot shows the local deposit thickness along one diameter, the way an OCT B-scan shows RPE elevation. Flood-fill connected-component analysis turns the continuous field back into a drusen count, largest equivalent diameter and AREDS size classification, exactly as the 3D model reports them.